PDF- Ford Motor Company, 2018 Model -sync handbook - Motorwebs - How to Modify Ford s.o.h.c Engines - David Vizard

ntains all the proffesional tuning proceedures applyable to Ford Pinto engines

Description

BY DAVIDVIZARD

FOUNTAIN PRESS LTD

Contents Introduction CHAPTER ONE

How Do We Make Horsepower

CHAPTER TWO

Heads for Power & Economy

CHAPTER THREE

Cam Drives,

Cam & Valve Trains

CHAPTER FOUR

Air Filters,

Carburation & Manifolds

CHAPTER FIVE

Exhaust Manifold & Exhaust System

CHAPTER SIX

Ignition Systems

CHAPTER SEVEN

Blocks,

Pistons,

Cranks & Flywheels

CHAPTER EIGHT

Lubrication & Cooling

CHAPTER NINE

Fuels &Water Injection

CHAPTER TEN

Nitrous Oxide

CHAPTER ELEVEN

Turbocharging & Supercharging

CHAPTER TWELVE

Building a C3 Automatic Transmission for a Turbo Engine

CHAPTER THIRTEEN

Off-Roadingthe Pinto Engine

CHAPTER FOURTEEN

Building the Engine for a Purpose

CHAPTER FIFTEEN

Dyno Tuning

Suppliers & Manufacturers Index

CREDITS

Writing a book like this is never a five minute wonder

A lot of time,

effort and hard thinking went into it,

but it would all have been for nothing if it had not been for the generous assistance of many people

Some people were able to help more than others,

and almost all helped as much as they could

My special thanks must go to Duane Esslinger,

Jim Flynn,

Carl Schattilly,

Denny Wyckoff,

Dave Egglestone,

Keith Roof,

Doug Somerville for many,

To these I must add the names of my able Australian contacts,

John Bruderlin and Doug Huntley

From here,

the names belong to people all over the English-speaking world,

so here are sincere thanks to all the following: Racer Walsh,

Steve Burton,

David Ray,

Bill Quinne,

Sig Erson,

Harvey Crane,

John Reid,

Barry Reynolds,

Ron Capron,

Ak Miller,

Jerry Branch,

Darryl Koppel,

Dan Swain,

Ken Johnson,

Mike Urich,

Derek Sansom,

Geoff Howard,

Bill Nelson,

Kevin Rottie,

Joe Antonelli,

John Campanelli,

Terry Davis,

Frank Casey,

Harold Bettes 11,

Gary Polled,

Mike Anson,

John Shankle and John Lievesly

To this I must add a special thankyou to Daphne for one year's hard typing

Introduction

The Ford Motor Company introduced their single overhead cam (SOHC) eng n e in 1970,

and since then they have been installing it in close on a million vehicles a year

This means that by now there are a lot of these engines around

In Europe,

this engine fulfils a number of duties ranging from everyday workhorse requirements to the higher performance needs of Ford's more sporting vehicles like the RS Escort

The same basic engine can displace 1300,

In some countries such as the USA,

only the 2000cc engine was used,

this being installed in Capris,

Pintos and Bobcats

This is Ford's universal engine,

a power unit designed to b e put to as many uses as possible

I had the opportunity to pull one of these engines apart not long after their introduction and from the racer's point of view,

I liked what I saw

At the time I was writing a technical chat page for Cars & Car Conversions magazine in England and I did not hesitate to extol the virtues of this engine,

as well as criticising some of the possible drawbacks as I saw them

I pointed out that this engine had all the ingredients for high horsepower outputs at modest cost

Its overhead cam,

I said,

b e capable of allowing this unit to produce in excess of 100 bhp per litre in normally aspirated form,

and tmce that amount per litre in supercharged form

With all it had going for it I expected this engine to be an instant,

overnight hit with the speed equipment companies and the general public alike,

just as the British Leyland Minis had been eleven years previously

You don't have to b e a student of automotive history to know that my enthusiasm was not shared by all and sundry

After my initial acquaintance with

many years were to pass before one came into my hands again

During those intervening years,

one of the great unsolved mysteries of life for me was

a few enterprising folk did spend some time making them produce more power but few,

remotely approached anything llke the true potential of an engine of this configuration

Those clever souls who did manage to produce reasonable horsepower from Ford's single overhead cam (SOHC) engine usually found a very limited response to their effortsby the public

About 1976 I became re-acquainted with Ford's SOHC engine

I became the proud owner of a MK I11 1600 Cortina GT

Although it was not quite the car I expected,

I grew very attached to the machine,

and as a result I slowly became more involved with the performance aspect of its engine

As time passed,

I began to formulate a theory as to why this engine had not achieved wholesale acceptance by motoring enthusiasts

Ford's European competition involvement is probably well known throughout the free world

Their principal competition engine is the CosworthIFord BDA four-valveper-cylinder engine

This unit is available from Ford at displacements from 1100- 2000

Power output in excessof 280 horsepower normally aspirated can b e achieved with this engine,

though for long distance events such as rallies,

Since Ford already possessed a highly successful engine,

it seemed to them to b e pointless to develop its poorer,

less-endowed cousin the SOHC engine

Having acquired the easy-to-come-by horsepower from the SOHC engine,

At time of writing (1983),

if you built an engine using Ford parts,

about 155bhp would b e the limit you could reasonably expect

I am sure you will agree this is not a lot for an almost bullet-proof SOHC engine

The argument that since Ford has the Cosworth in its stable,

why should it spend time and money on an alternative unit holds water except for one point: not everyone can afford the price of a four-value-per cylinder engine

On the other side of the coin,

a lot of vehicles are already equipped with the SOHC engine

If Ford has to date,

declined to explore the true potential of the engine,

? Many people tried their hand at making the engine go but precious few,

have actually found the key to unlock the true horsepower potential from this ' unit

You would think that the efforts of those who did make horsepower would b e readily received,

Unfortunately,

it appears that the reverse applies

The situation seems more akin to a castaway on a Pacific island,

Was this apathy on somebody's part

Ineffective lines of communication would describe it better

My low acceptance theory is based on what I have already said

It hinges on the fact that for an engine to be an instant performance hit,

we must see leadership from the factory to constantly keep the unit in the'public eye

Morever,

it must b e responsive to even the simplest modifications

The factory leadership we don't have,

but this situation is changing with the increasing popularity of Group I now group A competition (the use of mass-produced vehicles with factory speed equipment)

The engine itself is only semi-repon-

sive to simple modifications but highly responsive to the right modifications

Making horsepower is only a question of finding the weak link in the chain of power production events

Those few who did find the way to high horsepower outputs were not in a position to publicize their findings in a wholesale manner

Instead,

the information filtered down through the ranks so that now,

a decade or so after it introduction,

the engine is only now beginning to achieve the status it deserves

The validity of this theory will b e difficult to prove one way or the other but to my mind it contains enough seeds of truth to cause me to restructure the concept of this book

Normally I would start witl-1 simple,

bolt-on modifications and fronn

each subsequent chapter would delve deeper into the engine in the search for more and more horsepower and,

a good insight as to what you can expect the results of any modification to be

It should also allow you to get the best increase in performance for the money you intend to spend

If you are anything Not so with this engine

economics play a vital role a s'to what you can do to your vehicle

As I have already said,

it is only semiBearing these factors in mind,

I inresponsive to relatively simple,

con- tend to go straight into the engine and ventional modifications

This is part of deal with its idiosyncrasies first

When the reason for its slow acceptance,

and I you have a greater understanding of do not intend to b e found guilty of the engine,

w e will then deal with the further retarding matters

Indeed,

which falls into the intention is the reverse

more accepted bolt-on category

This Whether you are loohng for a big and the more complex task of building horsepower increase or a small one,

a competition engine will b e dealt with you need to have a reasonable under- last

In other words I will deal with the

Hopefull

this boc3k will give you comprising parts

CHAPTER ONE

How Do We Make Horsepower

I am going to stick my neck out and tell you that really there are no such things as speed secrets

If more power is required from an engine,

then improvements must b e made in one or more of the following areas: 1

Increased volumetric efficiency

Increased thermal efficiency

Increased mechanical efficiency

Let's look at each of these three factors in turn and analyse them in a little more detail

First of all,

increasing volumetric efficiency

In simple terms,

this means improving the breathing efficiency of the induction and exhaust system

When you realize that at 1,500 RPM a typical engine has only six thousandths of a second to fill or expel the gases in the cylinder,

you will realize the ease of doing so becomes important

To improve volumetric efficiency,

w e make changes to air filtration,

exhaust manifolds and silencers (mufflers)

Into this cauldron of parts,

throw the effect of the camshaft profile or

and you will begin to appreciate there are a lot parameters affecting the end product

While on the subject of cams,

I should point out that high performance cams very often (but not always) increase high RPM breathing at the sacrifice of low RPM breathing

In other words,

they trade low end performance for top end

Improving the breathing ability of the engine is the most important single factor affectingpower output

Because of this,

it's hardly surprising this book deals with various aspects of improving the volumetric efficiency in detail

Pay attention to that detail and you will find the extra power you are loolang for

The concept of volumetric efficiency is relatively easy to understand,

but the term thermal efficiency,

Let me explain: when a certain quantity of fuel is burnt,

it releases a certain known quantity of heat

All forms of energy are interchangeable

If our engine converted all the heat energy to mechanical energy,

it would have a thermal efficiency of 100% Remember,

the fuel is burnt to heat the air in the cylinder so that it expands and pushes the piston down the bore

The more heat the air contains,

the higher the pressure it reaches and the harder it pushes down on the piston

the heat is taken away from the air,

it will not want to expand as I much,

so cylinder pressures will b e lower and the power will b e down

Typically 80% of the fuel we burn in our engine is wasted heating up the rest of the world

The remaining 20% is all that is converted to mechanical energy to propel the vehicle

Heat that is'dissipated in the cooling system or goes out as hot exhaust is heat that the engine burned fuel to produce and did not convert to mechanical energy

The factors which affect thermal efficiency are important to those of you requiring fuel economy as well as horsepower

The principal factors affecting thermal efficiency ,are the quality and correct timing of the ignition spark,

proper atomization or vaporization of the fuel in the airstream,

correct cylinder to cylinder distribution,

and correct calibration of the carburettor to deliver the optimum aidfuel ratio

The compression ratio is also a factor

The higher thls goes,

the better the thermal efficiency gets

Reducing heat losses to the cooling and lubrication system increases the thermal efficiency

Lastly,

reduced frictional losses help thermal efficiency,

but this really comes under the heading of mechanical efficiency

As far as mechanical efficiency is concerned,

take to improve it is to build the engine to the finest tolerances possible

Things like con rod accuracy,

piston to bore clearances all affect the final frictional losses the engine will have

Care in selecting and establishing the right clearances when building the engine will produce higher mechanical efficiencies

The overall concept of building a high performance engine is attention to every detail,

In the following pages I will elaborate on the points that were touched upon here

I will give you the necessary details or acceptable ground rules so you can successfully build or modify an engine to your particular needs

CHAPTER TWO

Heads for Power and Economy

the challenge of coaxing extra horsepower from a modern cylinder head produces interesting (

Gone are the days when a little thoughtful use of the grinder,

were all one needed to get one step ahead of the competition

combustion effi- cessively large port will sometimes ciency and heat losses

To optimize the flow less air than a smaller one

The most important factor in cylinder cylinder head,

attempts must b e made head development is shape

This is the to lmpove all these areas

There is no doubt that cylinder head most important consideration with any design is a very complex subject

It is cylinder head modifications

The often regarded by laymen as being a shapes of the ports,

As a result,

bers 'and valves dictate just how effecNo Sir

and one of these is that polishing the tive that cylinder head will be

If you inports is the trick to make a head work

tend to grind your own cylinder heads,

These days sophisticated equipment Nothing could b e further from the truth,

don't worry about a polished finish

A is required to produce cylinder heads A polish does nothing to increase the rough-ground finish is usually entirely of advanced performance

Foremost ,powerofan engine

In fact on occasions adequate

among this hardware are the flow it can reduce horse-power

unfortuAnother myth you should dispel,

TEE STANDARD BEAD nately,

such equipment is outside the fi- especially with the Pinto,

is that big nancial means of most enthusiasts

They do not

an exThe first step toward improving a Fortunately,

I have over the i years acquired such equipment

FIG 2-1A TESTED BY: DAVID VIZARD MARCH 1977 160,

in the following pages I will detail cerFLOWBENCH: SUPERFLOW 300,

STANDARD PRESSURE tain easier modifications,

as well as DROP OF 2 5 H20 1 many more exotic modifications

all have been developed on the flow 140 bench and thoroughly dynamometertested

As a result,

the changes will help the engine develop the amount of power one would expect from a SOHC,

ELEMENTARY PRINCIPLES The production of horsepower depends to a large extent on air flow

If a head has insufficient air flow,

it will never produce good horsepower but good air flow or an air flow increase does not guarantee a horsepower increase

Sometimes achieving extra air flplkr into the engine may upset some other aspect of the engine's functioning,

leading to a situation where little or no gains are made

A rule which works almost 100 percent of the time is ifairflow increases and nothing else changes,

Other factors affect horsepower apart from air flow,

STANDARD FORD SOHC 2000 HEAD I

INTAKE: 1

EXHAUST: I

I I I I I I

VALVE LIFT INCHES

FIG 2-18 EXHAUST PORT

PORT ANOLE TOO SHALLOW

SHORTSIDE RADIUS TOO TIOHT

A section through an unmodified 2000 head reveals that if nothing else,

the intake port has plenty of area

PORT ANQLE TOO SHALLOW

RADIUS TOO SMALL E SEAT LVE SHAPE FLOW REDUCING EDGE

LOW SPEED AIR

N CAN BE FILLED IN WITH LITTLE OR NO RE-

FIG 2-1c

AIR FLOW PAlTERN IN STANDARD INTAKE PORT

mechanical contrivance is to understand the nature of the device

?his let us analyse the standard head in a little detail

Take a look at the graph Fig

This shows the amount of air that can be passed through the standard ports on a 2000 head

The dotted line starting on the horizontal axis of the graph is a typical maxim lift achieved

Follow it up until it meets the inlet flow curve

Then turn 90 degrees and follow it to the vertical axis

This indicates that the head flows 131

For a 1

this is not a very good showing

In fact the head,

As it comes

from the factory it falls short on many counts as far as air flow and its power potential are concerned

First of all,

especially on the intake are very constrictive to flow

Secondly,

the shape of the inlet valve is far from optimum

The port angle in the head is also disappointing,

because it closely approaches the worst angle possible for flow

And last,

the final approach to the back of the value is too short

In other words there isn't enough length of straight port behind the valve head to allow the air a more direct shot to the back of the valve

Interestinalv

Both 1600 and 1300 heads have shallower chambers and longer valves

This means the air can make a more favourable approach to the back of the valve,

especially on the floor of the port around the tight turn just upstream of the valve seat

Apart from its breathing ability,

the inlet port does suffer one other ailment: the port itself appears to b e too large for the engine

The resultant slow gas speeds allow fuel to drop out of suspension easier than if the port were smaller

A study of the air flow pattern in the port reveals that most of the air flows at the top of the port,

and the bottom of the port is almost redundant

Flow bench tests show that if the bottom of the port is filled in as much as l/4 inch,

almost no drop in air flow results

Any modifications to this engine must b e done bearing in mind that fuel dropout can occur

When fuel dropout takes place the engine will lose horsepower,

Any changes ' which help produce a more homogenous mixture entering the cylinders will usually improve the engine's performance in these areas

Straight away this should tell us two things about these heads: enlarging the ports is definitely out,

and polishing them is not a good idea because a coarse finish is more likely to reintroduce puddled fuel back into the airstream

A shiny finish will allow fuel to stay on the surface as a liquid or drops which will run into the cylinder ,

and subsequently pass through the engine unburnt

EXHAUST PORT The exhaust-port suffers many of the

Unnecessary shrouding by the chamber though,

The only shrouding suffered is caused by the proximity of the cylinder walls and there is little we can do about that

IMPROVING THE HEAD

Too many abrupt changes in direction mean bad flow through the standard exhaust port

Arrows indicate the prime sources of inefficiency

same ailments that the inlet port has

The valve seat geometry needs improvement

On the other hand,

The exhaust port shape,

is even worse than the intake port

its flow figures are way below those attainable by a highly developed port

COMBUSTION CHAMBER

I am not suggesting this he

Far from it

The factory designea tne head to do a particular job,

and this it does in a satisfactory manner

They did not desian it for racers and for high perilt will nee3d some redesignf o:mance ~ in(J

You may well Eisk if the re is anythlng that dl3esn't net

'me combustion cnamber is a very good design and has many factors in its favour

Many production cylinder heads suffer from what is known asvalve shrouding

This is the situatioi where,

ween the edge of the valve and thc

combustion chamber wall is insufficient to allow air out

On vertical valve engines,

the cylinder bore will almost always cause shrouding

Although the Pinto engine has inclined valves,

the inclination is not sufficient,

nor is it in the right direction to obviate shrouding

Valve shrouding caused by the unnecessarily close proximity of chamber walls to valve heads is all but non-existent on the standard cylinder head

The prime factor of an engine's power characteristics,

b e it a well developed unit or not,

Because of this,

I will deal in depth with head modifications and how they affect airflow

I will show precisely what modifications are needed to produce the required results

Improving airflow is finding the right combination of shapes

Two head modifiers starting off with the same basic head casting may arrive at two different combinations of parts and shapes to produce compatible airflow figures

And importantly,

trying to combine the specifications of one with the other may well ~roduceworse airflow figures than you s

A more precise C A ~ I let's I ~ say ~ ~ that ~ : somebody develops a trick valve shape which really turns the flow on with a standard port: There is no guarantee such a valve is goincI to work in the same manner if the port is steeply downdrafted

It all come

!sback to combinations of shapes

don't reckon on producing a super trick head by using what may appear to b e the best points of severa1 different heads

More than likely,

whafc3ver you do will b e worse,

as this is not a]n easy head to improve upon

The only way to find out what will work for

is by testincr on the flow bench and 3ULc dynamometer n

SIMPLE MODIFICATIONS My policy,

is always to try the simple modifications first in an attempt to extract the most for the least

In the category of simple modifications,

we have such things as multi-angle valve seat jobs,

removing sharp edges from valves,

plus going into the port with a grinder and just taking off any flash marks or sharp edges produced from machining in the port

I have news for you

the 2000 head does not often respond positively to such moves

In fact,

the first week I spent on the flow bench with one of these heads produced a large number of negative results

Whoever designed this head,

made it so you have to fight all the way to get any flow increase

Let's consider those multi-angle valve seats that are often touted as the trick thing for a few extra horsepower for next to nothing

I tried such valve seats on brand new heads,

the usual result is reduced airflow compared with the standard 30,

Ford putson the head

This doesn't mean we can't improve the head

it just means that an elaborate 15,

Take a look at the chart (Fig

To b e truthful,

tsking the sharp edges off the yalve makes things even worse

If you do any grinding on the back of the valve,

it must b e a substantial 30" cut as shown in Fig

For such a simple modification,

as you can see from the graph,

the flow was substantially increased

This led me to test many valve shapes to determine which

FIG 2-2 Comparison between standard valve seat and mun~rangleseat

Valve Lift In Inches

Standard

MultilAngle

NOTE: Standard width valve seat used in all tests

Test pressure drop 25" H20

MODIFICATION TO STANDARD INTAKE VALVE FOR IMPROVED FLOW TESTPRESSUREDROPZS"H20

TESTED BlDAVIDVIZARDIPAIL77

FIG 2-4 THIS SHOWS DIRECTION OF THE MAIN MASS OF AIR IN A 2000cc HEAD WHEN TIHE VALVE IS AT MID OR CLOSE TO FULL VALVE LIFT

Flow testing quickly established that the flatter the profile on the back of the valve and the thinner the stem,

the more air the port would flow

Velocity probing the port quickly showed the reason the flat valve worked best

If you look at Fig

rather than in a downward direction toward the valve head and around its sides

This shows that most of the air entering the cylinder FIG 2-5 ,

ValveLii In Inches 0

Test pressure drop 25" H20

exits the port on the plug side of the valve profile is the shape to have

and little air exits the port on the opposite side

A valve with a large tulip section on the back presents a consid- VALYE SEAT AREA erable obstruction to the airflow

A flat valve presents less obstruction and as a Any competent head modifier will result mid-lift airflow is increased con- tell you the most important part of any siderably as Fig

2-5 shows

This trend head modification is the area 1/4 inch in valve shapes predominates through- before the valve seat and '/4 inch after out all flow testing,

In other Because the multi angle valve seat words,

unless we put in a new set of proved singularly unsuccessful,

a new steeply downdrafted ports,

the flat line had to b e tried

The obvious thing was to bore out the throat of the intake port

This would give a useful increase in the breathing area

Such modifications don't always result in extra flow C

because very often the efficiency of the ,

Flat Back Valve StandardValve port may drop due to the abrupt changes in shape in the vicinity of the 12

However,

1 head,

this modification did work out

The easiest way to do this modification 42

This leaves you with a seat 119

010 inch,

The step produced 135

After boring the port,

A needle file can b e used for this,

The amount of chamfering required at this point is minimal

FtG 2-6

TEST PRESSURE DROP25" HZ0 TESTED BVDAVlDVIZAIDAPIILI7

MODIFICATION T O T H E VALVETHROAT2000CC ENGINE FOR INCREASEDAIR FLOW

FIG 2-7

TEST PRESSURE DROP 2s" H2o

MODIFIED SHAPE

MODIFIED SHAPE B

INLET VALVE GUlDE BOSS MODlFlCATlON FOR USE WlTH STANDARD GUlDE AND N O BRONZE GUlDE INSERT

THIS SHAPE IS BEST SUrrED TO CAMS GIVING VALUE LIFTS I N THE 0

have broken the corner with a ,010 inch wide cut,

The resultant increase in airflow is shown in Fig

At this point,

compare these figures with graph showing flow performance of a flat-back valve

All these modifications work using a more conventional valve with the back cut at the 30" angle

135 130

The proportional crain is similar but the results achieved with the more conventional valve shape are less than those achieved with the flat-back valve

Moving farther down the port brings you to the guide boss

Here you must make a decision

The guide boss

If you are buying a head and you are paying big money for a so-called trick head,

be very wary of one that still contains the guide boss,

as the head will flow more air with the guide boss cut away

Just how much cutting away needs to be done depends on the lift of the cam you will run in the engine

Look at Fig

Note that with no guide boss there is only a substantial increase in flow at lifts over

412 inches

It is unlikely you will see any benefit by cutting the guide boss completely away,

unless you are running with a cam of at least ,500 inch lift

Importantly,

cutting away the guide boss does bring about its own problems

Because the guide length is shortened,

valve guide wear increases drastically

The trick approach to running short guides without sacrificing guide life is to install bronze guide inserts

In the U

K-Line thin-wall bronze guide liners or Winona helical bronze inserts are commonly used

In Europe,

bronze guides are more commonly used

If you don't want to go to the expense of bronze guides,

you can still shorten that guide boss and make an appreciable gain in flow

Shape A of Fig

the shorter guide life will be

If you are using a stock cam,

modified shape A will probably b e good for around 50,000 miles

As cams approach 0

you will find guide life reduced to a s'little as 25,000 miles

Consider this guide life before you decide whether or not to use a bronze guide and the expense it involves

Moving on to the parallel part of the port,

you will find that this is critical

It is already too big for best results on the dyno

don't waste time giving it a super highpolish finish

In fact,

you can usually get the best results by not touching this part

The main thing to remember when you are modifying the cylinder head is that it's shape that counts more than finish

The shape can make hundreds of percent greater difference in flow than polish

All your efforts at this stage should go on careful shaping in the area around the valve seat and

When you've gone that far,

This flow bench model valve gave almost as much airflow increase in a standard port as a complete porting job gave with a standard valve

INTAKE PORT DEVELOPMENT So far,

simple modifications to the intake port have been considered

Now let's begin to get a little more exotic while retaining the standard size valve

If you are good with your cylinder head grinder,

a venturi around part of the valve seat will p e p up the flow

This works with either a re-profiled standard valve or a flat profile valve

Such a venturi shape will not generally increase peak flow but it certainly does help in the all-important mid-range flow

Remember,

the valve reaches full lift only once in the lift curve but it reaches half-lift twice

With the venturi,

substituting the conventional shaped valve for the flat profiled valve pays off with even greater flow

See Fig

F I G 2-8

This head is being prepared at Shankle Automotive

A lot of attention is being given to the shape of ports and chambers

However,

a chrome-like polish is nowhere to be seen

This is as it should be

INCREASING PORT FLOW AM) only about two-thirds the velocity

I will VELOCITY not spout lots of different numbers So far,

all tKe re-shaping w e have considered has been done by remwing metal only from the port

But let us consider this problem of the too large a port diameter

W e can largely overcome this by adding material to the port,

which on the inlet side is not too difficult to do

A material or bonding agent with metal in it,

such as Devcon or an epoxy resin such as JBs Weld,

makes a good job of putting material back where it's missing

The point is,

where should w e add it and what sort of velocities do w e need

? If a comparison of the air velocities in the port of a 2000 engine is made with,

INCREASE I N AIR FLOW W l'T H VENTURI VALVE THROAT

TEST PRESSURE DROP 25"H20

75rma,io

VENTURI EXTENDS ONLY AROUND THIS SECTION

WlTH VENTURI

WITHOUT VENTURI

NOTE: BOTH TESTS USE FLAT VALVE VALVE LIFT

suggesting that you should have this or that port velocity

Port velocity is a subject which is very much misinterpreted

The thing to consider most when juggling with port velocities is that the prime objectives are to achieve a higher and more even port velocity so fuel stays in suspension and better inertial ramming of the cylinder

Dyno testing indicated that reducing the port size while retaining the same airflow in cubic feet per minute gives a worthwhile increase in horsepower

This is especially so if there is no intake charge heating present,

as is often encountered on factory manifolds

Even if intake charge heating is present,

w e can still come out on the winning side with more power and economy by not aggravating fuel dropout

Let me give you an example

Some time ago,

I was testing an engine with engine builder David Ray

This engine had a very high specific fuel consumption

Its thermal efficiency was low

The head had fully re-worked and hlghly polished ports

This head was then substituted with another head with a rough intake port

Only the area in the immediate vicinity of the valve had been reworked

Airflow of both heads was about the same

The rough port head produced its best horsepower with a secondary barrel main jet two sizes smaller than required for maximum power letting for the polished port head--this engine produced 1

5bhp more

! Summing up: the rough-port produced more horsepower on less fuel

Adding material to the port to increase velocity is all very well but the

FIG 2-9 Comparison of conventional port shape V ramp port

The "ramp port" was a successful experiment as far as airflow and gas speed were concerned,

but its shape was rather too critical to produce even on a four-off (one per port) basis

? Making the port into a D-shape by adding material to the floor will decrease the port size and galn the higher gas velocity required for better fuel suspension without significantly affecting the airflow

Usually,

only a very small reduction in airflow occurs

However,

it would b e much better to see whether material could b e added so as to increase airflow as well as increase port velocity

To do this w e need to plot out where and in which direction the air is moving in the standard port

The drawing on an earlier page tells us most of the air is travelling along the ceiling of the port when the valve is at working lifts

air flowing at the top of the port makes good use only of the far side of the intake valve to feed the cylinder

If the core airflow can b e moved so that it utilizes a greater amount of the intake valve,

an increase in both port velocity and airflow are likely to result

Many hours experimentation were done along this line and it resulted in a port which,

I call a ramp port

With the ramp in the intake port as shown in the photographs,

airflow was increased as shown in Fig

and port velocity was evened out to a much more consistent figure

The curve on the ramp also tends to direct any fuel that is running low down in the port into the centre of the cylinder,

rather than onto the cylinder wall where it is unlikely to burn

The addition of the ramp produced a port velocity which fell in line with many engines known to produce good specific fuel

Lift Inches

Conventional Port

Ramp Port

Standard pressure drop 25" HzO

Valve Dia 1

Making this ramp is a difficult job

To begin with,

a rough form of the ramp needs to b e added to the port,

followed by the final shaping,

which must b e done in conjunction with the flow bench to make sure it's working right

It is not really a job for the amateur head modifier

Fortunately,

the ramp does not need to extend upstream into the intake manifold

I tried this with a 45 Weber manifold and all I succeed in doing was reducing the total airflow

My advice: if you intend to build a ramp port,

do it as shown in the photos and leave it at that

To make sure you don't have some Devcon or JB Weld disappearing into the engine,

b e sure when you use it that the port is totally oil-free

Also grind some grooves in the FIG 2-10 SIMPLE COMBUSTIONCHAMBER MODIFICATIONS REMOVE SHADED AREAS OF COMBUSTION CHAMBER,

BUT W NOT GRIND PAST GASKET LINE

ONLY if larger valves are used does the combustion chamber require any significant reshaping

Even when ground to suit a larger valve,

the chamber still retains a similar appearance to the standard shape

This photo of a virtually finished big valve chamber,

when compared to the standard chamber

MARK OUT GASKET LINE

base of the port for the Devcon or JB Weld to grip securely

An engine which swallows a lump of the intake port isn't going to produce as much horsepower as it should

COMBUSTION CRKMBER

As long as the standard intake valve is used,

the combustion chamber suffers no unnecessary valve shrouding,

apart from that caused in the area adjacent to the cylinder wall

you should lay the head gasket on the cylinder head and mark out where the gasket comes to

Then cut the combustion chamber wall to that line

This will give the air the maximum chance of coming round on the chamber wall side

The same situation also applies to the exhaust valve and the same technique can b e used to grind the combustion chamber to the limits of the gasket to relieve the exhaust valve of any unnecessary shrouding

COMPRESSION RATIO Some easy increases in power can be achieved by raising the compression ratio

These engines are available in a variety of compression ratios

Those with ratios in the range of about 8:1 respond very favourably even to only small increases in compression

As a rough guide,

050inch (1

21mm) off

Machiningthe head face to raise the CR is an easy way of boosting power and economy from your Ford SOHC engine

the head raises the compression ratio about 3/4 of a ratio point,

Typically,

these engines will respond with about a fiveto-seven-percent increase in torque and horsepower

Because the power increase is brought about by more efficient use of the fuel,

In some areas of the world,

the octane rating of available fuels is little better than that of peanut butter

Once compression ratios start exceeding about 9

Where 100 octane fuel is available,

compression ratios up to about 11

5 or 12

As compression ratios increase,

less metal has to b e taken from the head to raise it a corresponding amount

For instance,

if it took ,065 inch to raise the compression ratio from 8

it will probably only take another ,040 inch to raise it from 9

3 to 10

About the maximum that can b e machined from a 2000 head is 0

165 inch

For now,

we are dealing only with minimal compression ratio rises to obtain cheap and easy horsepower increases for normal street purposes

we'll discuss the matters of maximum compression for maximum power

From the factory,

the compression ratio on these engines is altered

through the crown height of the piston

RS 2000 engines already have a compression ratio a little in excess of 9:1

Forty thousandths off the head on these would put the compression ratio close to 10

Don't b e too greedy on compression ratios for street engines

Overdo it,

and you may ultimately incur further expense by either measures to suppress detonation or lowering the compression ratio

One means of suppressing detonation with very high compression ratios is the use of water injection

and its effects on horsepower and emissions are dealt with in Chapter 9

To get your engine's compression ratio raised it will b e necessary to take the head to a motor machine shop and have the required amount machined off

Before reinstalling the head,

be sure to remove the sharp corners from the edges of the combustion chamber left as a result of the machining operation

If this is not done,

the possibility of pre-ignition is greatly increased

A needle file is the simplest means of taking off these sharp corners

SIMPLE EXHAUST PORT MODIFICATIONS So far,

ways and means of filling the cylinder and effectively burning the mixture have been dealt with

Once the mixture is burnt,

the gases must b e expelled as efficiently as possible

Ineffi-

FIG 2-1 2

MODIFICATION

" TO PORT JUST BELOW VALVE SEAT ON SHORT SIDE (TIGHT RADIUS SIDE) OF EXHAUST PORT

VALVE SEAT WIDTH EXAOElUTED F011MICE OF C U R m

DOTTED U N E REPRESENTS

DRAWING FIG

VALVE L'I F T

cient exhaust ports not only cost horsepower,

An exhaust port which does not flow very efficiently causes higher pumping losses on the exhaust stroke

This saps power previously generated by burning fuel on the power stroke

The simplest,

most effective modification to the exhaust port is to reprofile the valve as shown in FIG

This involves radiusing the chamber side of the valve and back-cutting the back face of the valve on a valve seat grinder to the 30" angle shown in the drawing

This results in flow increases of up to eight percent in the mid-lift range of the valve lift cycle

krflow over ,400 inch llft changes little

This suggests that the port is limiting the flow at valve lifts of this height

Although it's not the raving success one would wish for,

a multi-angle valve seat job on the exhaust does help the situation a little

At lifts up to ,330 inch,

flow is increased a worthwhile amount

However,

The trade-off is definitely in favour of the multi-angle valve seat but it's certainly nothing to write home about

If you have a high-speed electric drill or a small high-speed grinder,

then five minutes' grinding in each exhaust port will considerably aid the flow

After the multi-angle valve seat has been cut,

grind the short side of the port as shown in Fig

I should point out at this stage that you need a steady hand

If you slip and gouge the valve seat,

you will have to have it re-cut

The graph shows that this grinding operation pulls up the mid-range and top end flow considerably for such a simple modification

Basically,

it's allowing more area for the air to pass out of the cylinder and it's making more effective use of the area available in view of the direction the exhaust gases are moving when higher lifts are attained

The tight curve on the short side of the port is so acute that the exhaust flow in this area at high lifts is minimal

At low valve lifts,

where the speeds are highest right at the seat,

the exhaust is able to make it round this corner without undue problems

Enlarging the throat area immediately under the seat helps the midrange flow

If further gains in the exhaust port are intended,

you'll have to get deeper into the port and make some substantial changes to its shape

Looking down the

FIG 2-14

EXHAUST PORT RESHAPING FOR U S E W l'T H STANDARD VALVE

This kink and the proximity of the port wall opposite is responsible for flow loss,

but to remove it effectivelyentails grinding quite a bit of metal out of the port

A profile you should aim for is in Fig

HOW MUCH HORSEPOWER INCREASE

? So far you have been presented with ways and means of increasing the airflow potential of the head

But when we get right down to it,

it's not airflow that gets you down the road,

it's how much horsepower your engine has

The question is,

if you have done all the modifications suggested to improve the intake and exhaust ports,

plus raised the compression ratio about one point,

what sort of horsepower increase can you expect from a typical 2000cc engine

Curve number 1 is a standard Escort RS specification engine

The compression ratio is 9: 1 and the engine ran on the dyno less the air filter element and with the dyno exhaust system

As a result the horsepower figures for the standard engine are slightly above those obtained in the as-installed condition

TEST PRESSURE DROP^^" H20

TESTED BV DAVID VIZARD MAY 77

NOTE:TO MUCH METAL REMOVED HERE WILL BREAK INTO WATER JACKET

&SEAT 6 THROAT MODIFIED AS SHOWN I N DRAWING FIG

VALVE LIFT

Curve number 2 is the horsepower output of a cylinder head utilizing all the simple modifications described so far

The compression ratio on this engine is 10

This requires 100 octane fuel,

water injection with lower octane fuel

BIG VALVE BEADS We will deal first with the Group 1 (or

FIG 2-1 5 FIG

TESTED BY: DAVID RAYIDAVID VIZARD OCT

OXFORD,

ENGLAND

TESTED BY: DAVID VIZARD OCT

CORRECTED TO STANDARD TEMP 6 PRESSURE

FLOW BENCH: SUPERFLOW 3M) STANDARD PRESSURE DROP: 25" H 2 0 2

1201 100-

FORD SOHC 2000cc HEAD BUILT TO GROUP I SPECS 1 INTAKE VALVE 1

SO (38mm)

RPM STANDARDHEAD MODIFIEDHEAD 2500 47 50 3000 62

4 3500 77

5 4000 87

3 4500 98

9 5000 105

7 5500 99

ENGINE RPM x 1 0 0

VALVE LIFT I N INCHES

available from Ford in ~ n g l'a n d'

This is a specially selected casting machined to accept larger valves

The valves employed in a Group 1 head are 1

If you are going to compete in any sort of competition where Group 1 rules apply,

you have little option but to run with this cylinder head

An out-of-thebox Group 1 head gave the flow figures shown in Fig

A comparison with the flow curves given by the standard head shows that the increase is not very substantial

If this engine is to be competitive,

then Ford will have to develop a better Group 1 head

My own flow and dyno testing has revealed a rule-ofthumb formula which is useful for predicting approximate maximum power output from a 2000cc engine,

based on the airflow of the inlet valve: Horsepower 1

when intake cfm is measured at 25 inches HzO

OR Horsepower = 1

when intake cfm is measured at 10 inches Hz0 For this formula to 'be even close,

several conditions must b e met: first the exhaust flow should b e about 70 percent of the intake flow at comparable lift

It also assumes that everything else

connected with the production of horsepower is at least more than adequate for the job

By this I mean that there is enough carburation or fuel-injection breathing area,

the cam has adequate lift and timing for the horsepower to b e produced,

the exhaust has correct length and zero back pressure,

With the optimizing of all these items,

the head should b e left as the limiting factor in the equation

If it is,

the formula works quite well and an example looks like this on a Group 1 engine: Airflow at 0

Using the formula,

05 = 151

As it happens,

even the best Group 1 engine builders are hard pushed to beat the 155 bhp mark

Considering the fact that this is only an approximation formula,

it has proved to b e fairly accurate and rarely seems to b e off more than about 10 horsepower

If you are going to build a legal Group 1 head,

(rules as of 1978) then little can b e done to increase its flow potential

Hand grinding,

unless originally done by the factory,

is specifically prohibited in preparation of the head

In other words,

unless the factory does a porting job on the head,

you cannot do one yourself and stay legal

You can,

do machining work on the valve seats

by reducing valve seat width to a

a little extra flow can b e achieved at the expense of valve seat life

The intake valve seats can b e narrowed down to

Omm)wide,

and the exhaust ones to about ,050 inch (1

If you pr'epare the exhaust valve seat and the exhaust valve with with the same machining techniques as described for the standard head,

it is possible to achieve similar flow increases on the Group 1 head

exhaust flow increases noticeably in the all-important mid-lift range of the valve

As far as the intake is concerned,

you may b e able to use a substitute intake valve in some forms of Group 1 competition

Here you must check with your rulebook or tech official

The intake valve I recommend is one of my design manufactured by G & S Valves or the 'Rimflo' valve produced by Specialized Valves

This type of valve is available in the US,

through such companies as Branch Flowmetrics,

Esslinger Engineering and Racer Walsh

To stay within Group 1 regulations this valve must b e slightly reduced in diameter to 1

As it comes from G & S,

Substituting this valve for the Ford Valve in a Group 1 head gave flow increases as shown in Fig

I tried many other shapes,

plus proprietary brands of Pinto valves,

and could not find one which could out-

FIG 2-17

STANDARD PRESSURE DROP: 25" H 2 0

GROUP I PROFILE

PROFILE

This shot shows the radical shape difference between the factory Group 1 intake valve and the high flow valve developed by author David Vizard

flow elther of these valves In any configuration of Pinto head where the standard port angle was retamed

NON-COMPETITIVE APPLICATIONS OF GROUP 1 HEADS Many of you will no doubt b e considering buying a Group 1 head for no other reason than to bolster the performance of your road- going machme

Here I should point something out: you have only to make a comparison of the flow curves to see the standard Group 1 head is inferior to reworking your existing head to even the simplest specifications described earlier If you want to spend the sort of money involved in buylng a Group 1 head take my advice-don't Spend the money on valves and have your existing head reworked You will get more airflow and more horsepower for your money Actually,

there aren't many advantages to buying a Group 1 head for any application except Group 1 racing The notable ones are (1) You get a selected casting which may b e slightly superior for modifying,

it may b e a stronger head casting

To some,

even thls benefit is of academic value only (2) If you are modifying the head yourself,

you will have less work to do in the valve seat area because the head ls already machlned for larger valves

If maximum flow is the object,

a lot ofwork will have to b e done on the valve seats but not as much as starting with a standard head

Here is a side-view of the intake port described in the text

It has been moulded in Blu-Silsilicone rubber which,

is easily removedfrom the head

Note the large bulbous radius on the top side of the port

BIG VALVE CYLINDER HEADS Does a normal engine,

which is only required for high performance on the road,

require the ultimate in cylinder heads' When talking about the ult'mate m cylinder heads,

one should consider expense as well as practicality My advice ls,

if your pocket book will stretch far even for road applications,

but you wlll galn top-end performance

(This assumes of course your e n m e s'cammed m a slutable manner ) Let m e give you an example

My norma1 road-gomg Pinto 2000 automatic uses one of my head configurations,

which on the flow bench produced a lot more airflow than many current race heads

Thls engine works fine with the standard torque converter and produces almost double the horsepower at

The widening of the intake port starts about 3/4" before the valve guide

Because of the proximity of the chamber wall,

the general direction of flow needs to be biased towards the centre of the cylinder

This is partially achieved by taking a little more material from the cylinder wall side of the port than from the other side

the wheels that the original engine did

Thls is achieved with head,

cam and exhaust-manifold changes

This should bring home the point that Ford's SOHC engine needs every bit of breathing it can get

While producing this extra horsepower,

the engine still met and even surpassed all its original emission standards

Moreover,

than it originally did Thls rule of striving for maximum airflow should b e considered valid only insofar as your finances permit

You can draw the line when weld material must b e added to the ports

When you begin building completely new ports,

then the expense is seldom justified for a road machine You should look for other more economic ways to improve horse-

DRAWING FIG 2-18

VENTURI ON THISSIDE ONLY

E & F: DOlTED LINES SHOW ORIGINAL PORT

ORIGINAL PORT SHAPE IN VICINITY OF VALVE NOT SHOWN TO IMPROVE

FIG 2-18 DRAWING TESTED BY DAVID VIZARD JULY 77 FLOW BENCH SUPERFLOW 300 STANDARD PRESSURE DROP25" H Z 0

-SOHC2000cc HEAD

This head representsclose to the ultimate in workmanship but r i l'e in the way of headmanship for horsepower as the text explains

VALVE LIFT

AIR FLOW CFM

FLAT PROFILE VALVE 3-PROPRIETORY HEAD MODIFIED AS SHOWN IN ACCOMPANYING PHOTO 4-STANDARD HEAD WlTH STANDARD VALVES

VALVE LlFT

FIG 2-19

COMBUSTION CHAMBER MODIFICATIONS FOR OVERSIZE INTAKE VALVE 2-15

The Manley valve,flatter of thetwoshown here,

Not only is its stem highly wear-resistant for long life,

but its shape also proved superior to the high performance Ford item pictured alongside

RADIUS EDGE

EDYF== 0

AIRFLOW CFM VALVE STANDARD MODIFIED LlFT CHAMBER CHAMBER 0

1 74 47

349 130

436 172

523 180

61 0 187

CHAMFER BACK FACE 0

VALVE 30' TO PRODUCE VALVE SEAT WIDTH SHOWN FIG 2-20

EXHAUST VALVE PREPARATION

FIG 2-21 FLOW DIRECTION BIAS ON EXHAUST PORT

ARROWS SHOW THE PREDOMINANT DIRECTION OF AIRFLOW FROM COMBUSTION CHAMBER WHEN EXHAUST VALVE IS IN ITSMOST OSEFULWORKING RANGE

THIS IS NORMALLY BETWEEN 0

This is the shape of the exhaust port at the manifold face,

M~~~of the flow takes place at the top and the righthand side of the port

2-19 8120

These two photos show the side and top view of the port that gave the flow figures shown in Fig

The centre of the cylinder is on the right of this exhaust port moulding

The flow direction bias shows up as a "lean" to the left

FIG 2-22

EXHAUST PORT MODIFICATION FOR 38 or 39mm VALVE EDGE OF PORT LEVEL WITH EDGE OF MANIFOLD STUD

Turbocharging or adding nitr- d'e r head is equipped with a 1

then the valves might more sophisticated carburation won't actually touch until lifted about or even a cam change

Frequently,

The rules for competiton engines call for a Pinto cam hasn't yet been built with an specific stage of modification and a overlap figure which is so much that

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