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How-To Section: Build a high perfomance Pinto


High performance pinto

There has been a lot of “mud” slung at the old Single Over Head Cam ford motor, over the years.
Starting with the rockers being no good and the inlet tract can’t flow enough air.
I believe these are all inter-related.

Starting with the standard [Std] rockers:
The Std rockers are just fine with Std springs which are about 40 lbs. of pressure at valve closed. Its only when you up-rate the cam and springs that the Std rockers are stressed. This led the performance industry to be conservative with cam profiles etc. , which in turn, led to achieving less air flow via the port. Materials have come a long way too. So if you get a cam, get a full kit. Also try to move away from cam specs of old and try one of the latest grinds. The major cam manufactures are now producing shafts that are far superior to old, with relation to ramp speeds etc.

I have had a bit to do with this motor and whilst mine isn’t the fastest/best HP I can tell you about it and recommend the combination that will get you at least 180HP. It started even before I had a car for the engine. I got a used head off of a friend to modify. This was to be the test mule.

After lots of reading of various books, I had decided that down-drafting the ports would be the quickest way to more flow. With this in mind I made a jig to mount the head in a vertical mill, to bore the ports out at various angles, then to insert a tube that would be curved to achieve a pipe for the carburetors to bolt onto after fitting a flange, similar say to a Lotus head. Well this was all good in theory, however achieving a seal between head and pipe, inside the port, was to prove elusive, thus far. I did get some “trick” putty from the states that was on paper the answer to this, The port at “d” and “c” in the picture were bored at different angles to see what would be the best. It became apparent that raising the port roof gave the best shot at the valve as far as air flow was concerned. This led me to drill holes around the port to find out how much metal was able to be removed from the upper port area, as in port “a “ in picture. I then ground a port out to what I believe to be a safe limit as in picture “b” . From this a template was made.

However I decided to travel down a different path. The above is also something for the future. By this time I had a car with an engine that a reputable engine builder had developed with filled inlet ports. At about this time a friend purchased a completed head from a supplier that was said to flow about 200hp of air. Both heads were fitted with 44 and 38 millimeter [mm] valves of flat back design. He and I had our heads flowed on a Super Flow 110 Flowbench. My friends purchased head, outflowed my filled port head, in all areas. I then proceeded to modify the fillings as they seemed to make the port smaller. This had little affect. The exhaust ports were ported very similarly in both cases. It is interesting to note that the recommended port bias Inlet to Exhaust is approximately 75%. This is achieved, leading me to suspect that a smaller exhaust valve and bigger inlet valve could be used, with more extensive work preformed on the exhaust port, however at that stage I was very happy with what I had learned, but certainly something for later also.

I then proceeded to copy friends head, which essentially was ported with the best shot at the valve when looking down inlet port. I use an air die grinder to remove material. I have used an electric one but found it hard to control. The best units have a remote motor with an extension drive to a chuck system. I don’t have that much call for one so I make do with what I have collected. Grinding bits are varied to suit the job. You can buy kits, with all the parts you need, these days.

I replaced all the valves with ones of same diameter. Mainly because the valve colletts were worn. This is something to be aware of when using strong springs and/or inferior valves. One thing to try to slow down the wear rate is to stop the retainers and colletts from spinning about the valve. This can be achieved by grinding the sides of the colletts till there is a gap between them when they are fitted to valve stem. Also be aware that the retainer to head distance [spring length] will increase. The new valves were sourced from England.

I never got to flow the finished head. It is fitted with a Crane 310-8 cam and their springs and retainers. This is certainly not the hottest cam around but is suited to the revolutions that the Std modified rods will withstand. When setting up a head you must check the wear area on the rockers. This is perhaps the most important thing to check. The wear area needs to be in the centre of the cam pad. If the cam runs off the end of the pad it will wear out very quickly. Placing it away from the centre of the pad means that the cam profile will be accentuated/de-accentuated. Machining is needed to correct this situation.

The inlet manifold was moved up on the head so that bottoms of inlet tracts were almost level. To achieve this the mounting holes had to be filed to suit. The manifold was then doweled to the head and finish ported whilst bolted to it. To match up to the oval shaped port that I described previously would have ment a new manifold would have to been made. I use bolts to hold the manifold on as this makes carburetor removal possible with air cleaners on. I use off the shelf “Genie” brand 4-2-1 extractors. These have had the manifold port upper and side part of the ground away [matched], to match the port shape. The bottom is angle ground so that the head to manifold face is lined up but as it moves away from port it is sloped upward. There is a definite mismatch to prevent exhaust reversion. The rest of the exhaust consists of 2.5 inch tubing with a round resonator under the boot floor.

Pinto’s like a high compression ratio. This may be to aid with a poor combustion shape. Above is all with a 2000cc head so high compression domed TRW 11.5:1 pistons are used. Even then the head has to be shaved. This engine is running 12.4:1 ratio on 100 octane fuel.

In hind sight it would be best to have flat topped pistons with say a 1600cc head that achieves the required ratio through a smaller chamber. This would aid gas flow into the chamber. The pistons need to be set up so that at the top of the stroke they are approximately 30 thousandths [thou] of an inch from the head. I highly recommend a Felpro head gasket. This means that the pistons will protrude from the block some distance. Approximately 8 thou. As the compressed height of a Felpro head gasket is 1 millimeter [38 thou]. This all needs checking at assembly time. Valves need to be approximately 70 thou from the piston, at all times. The pinto needs clearance around the spark plug. A groove needs to be in the piston to aid flame travel. One thing to watch out for at these levels of compression is the bottoming of the head bolts in the block.

Conrods in this engine are early style with floating pins, lightened around the small end with 3mm material left, and also on the bottom of the big end.. When doing this you need to lighten the heaviest rod first then work others to this weight . A 3mm hole needs to be drilled in the top of rod to allow oil to the piston pin. I use Automotive Racing Products [ARP] Conrod bolts. This combination has been very reliable for a 7500 rpm limit.

The crankshaft is relatively standard. They have large radius fillets. I have approx. 3 thou clearance on the rods and main bearings. This doesn’t seem to adversely affect oil pressure, though I am using a high volume pump.

The flywheel needs to be as light as practical and doweled to the crankshaft. I am currently using a slightly modified Escort sump. Engine was fitted with a Cortina sump that gives more oil capacity, however there were spacers under the engine mounts to raise it. Even then the lower part of the sump was below the cross-member. The escort sump has had the baffle removed and remade. It is larger in size [fits sump walls better] and the pick up and dip stick holes have their lips turned down. This combination has not lost oil pressure on any corners. I also use an oil cooler. The next step forward here would be a gated sump with extra capacity. The 2 litre engine oil capacity is relatively low.

Engine is fitted with twin 45mm Webber DCOE. Carburetors.
The carburetor internals fitted to this engine are :-
38mm chokes,
No. 4.5 Auxiliary venturies
No. 2 Needle valves
No. 40 accelerator pump jets
No. 50 F9 idle jets
No. F2 Emulsion tubes
No. 150 Main jets
No. 195 Air jets

Other Bits and pieces.
I had most of the internal engine parts coated with a kit that I got from the states. I am unsure of the affect on power that this will give. I look at it as mainly for durability. I had the springs, valves , conrods and rockers, pistons and head coated in various substances as to the kit instructions.

It is essential to set up the cam timing to cam manufacturers specifications. I use the Esslinger way as it is fool proof. It is also good to read their assembly instruction before you start.

The cam belt and timing can be a bit tricky, so beware here too. The valve clearances need to be set at the cam to rocker junction.

One bit of trouble I have had is the Welch plugs/core plugs falling out. This could be because of block flex, it is relatively easy to fix with some small fasteners.

You will need a better starter than the standard unit. The standard unit really struggles with the added compression, especially when its hot.

This extra compression also leads to colder spark plugs. Above motor runs happily on 2 grades colder spark plugs.

You will need a 3 core radiator to prevent overheating. Please use electronic ignition.

Webber carburetors need about 2 to 4 PSI of fuel pressure to work effectively. However they need a lot of fuel. You will need an electric fuel pump and suitable regulator. I use 9.5mm fuel lines.

Please use a rev limiter, other than your right foot.

The above engine will idle at 900 rpm, although it is happier at 1100rpm. It pulls from 2000 rpm in top gear. It has power till 7200 rpm, which is perfect for the conrods in it. When it was dynoed, the tyres were let down to 8 psi. A mate and I had to sit in the boot so that the tyres would grip the rollers. The dyno operator was very happy with the pulling power of it also. All on a Dyno Dynamics Dynamometer.

I would like to hear from people who have some other ideas, as I am building another engine soon. I have written above so that new comers to this engine will not be discouraged from trying to do their own engine.

Roger Miller


Pinto engine assembly notes

I have built a few motors in my time. Haven’t had any failures, yet. However, the outside work was kept to a minimum.

Let me tell you about the ‘pinto’ engine for my escort.....

Sent it to have machining done. Gave them a list of things to do, it sat there for 3 weeks till they decided to do it all in a few days. So pick it up and go home to start checking it out.... Conrods look funny, surface finish doesn't look like before. Look at other standard rods I have here. The machine shop has sand blasted them instead of shot blasting them. I had already polished & lightened them. Wrote on my job card to have new bolts fitted, re-sized, small ends floated & shot blasted after balancing.

So take them back.
About this time I ask why I had them put dowels into crank as I am dealing with the boss this time. His answer is "because you asked us to". Words fail me. I point out that they have a tendency to part company from flywheel, & that they really should be bigger & more than 2 of them at .25 inch [6 millimetre] in diameter! He informs me that “they will never break and are super hard”. Well they ain’t yet, however I will be taking off slightly easier than I had wished to. Anyhow 3 visits later on a Saturday morning I wait as he re-sizes conrods after being blasted.

So now I can dry assemble the engine. Start with the head. I am using new valves which are slightly longer than previous, no lash caps this time, so after setting it all up cam, rockers, springs etc. the cam lobes run off the end of the exhausts rockers only. Also all the rockers are touching the retainers. Crane dished retainers [e.g. use longer spring.] ......lots of swearing about now.

After linishing the edges off of the rockers so they don't touch retainers I am having trouble getting the correct spring pressure, way too much. Drag brother around so he can look at it, 2 heads are better than one etc. I suggest to lower the valve into the chamber by putting exhaust valve seat inserts into the head. He says that will work and we then set about finding how much. I have some 1 mm shim which we sit between head and valve. This seems to about right. However, brother suggests to ask the experts at the machine shop. So back I go to explain to him what is happening. He has a vague idea about what I am talking about and suggests to grind the cam lobes smaller!!. So I asks him to put inserts into the head, 1 mm further out of the head & to machine the valve seat pockets the same amount.

I Collect that some days later. Re-assemble it again, near enough to perfect, well actually some 10 pounds too much pressure at full lift but hey, what's a guy to do! CC's chambers, work out to achieve compression ratio needed, I need 40 thou off head, so back it goes to machine shop again. So all well there, matches manifold to head, dowel it with a roll pin in manifold, little touch up on the exhaust seats that he fitted.....wallah!

So onto the bottom end now all seems ok there . Tons of clearance on bearings. Head bolts are close to bottoming out into block so get away with tapping them out with a bottoming tap.

Now off to the coatings place with it all. I had approached him earlier he is ok to do the job and seems eager to do it as he is just starting out and wants the experience with engine parts as people mostly want exhausts etc. coated. Anyhow he gives me a great deal. So I drop off parts to him. He is quite busy and I don't want to push him in fear of a shitty job. Anyhow 3 weeks go by, so I go check him out. He has most of it done & completion will be by end of that week. I pick it up, to find the cam bearings are cooked [read melted] & need replacing. He is very apologetic & says to get new ones & he will coat them, offers a third off the total price, which I decline as he has done a good job, so far. Take it all home to find mains & conrod bearings are missing from package. Too late to go back, so return Monday night after work, he is sick & no one knows where they are. Employee rings him to find that they got missed & he will coat them later in week with new cam bearings. Another week goes by & I turn up to collect, to find that he hasn't coated mains & conrods. He says to use the fine powder from the kit on them. I take them & go home.

Now the final assembly.......
Start with the bottom cleaning etc. Notice that all of a sudden there is a big gap in one of the "o" rings around the block. Brother & I both say we would have noticed this earlier......I check my pictures and can see that it is a complete circle, no gaps. So I take it back to machine shop [by now, my car knows the way there so I just sit back and relax as it will drive itself !]. I See the bloke running the place, not Boss. He says it will be fine. [3 mm gap!!!] I ask to see the boss, he says “he is around corner”, “where I say” off I go. Boss takes one look starts shaking his head. Turns out that they farmed this out to some other company & they must have put a small piece in there to bridge a gap, which we must have dislodged when cleaning. So they send it back. I gets this back the same day! [message there some where] However these rings would later cause problems.

Again with the cleaning. Crank & bearings in, bolts tightened etc. Pistons onto rods........No 1 pin awfully tight, in fact, can’t get it in! Lots of measuring. Aww-shit! Looks suspiciously like rod has been damaged on little end aaaaaaaarrrrrgh! So small end is ever so slightly damaged....what to do. Reaming it out will make hole bigger all around. So decide to use fine sand paper on end of round rod to dress high spot. Lots of care here and much checking produces a very good result.

So back to it.
Rings on, pistons in, head on etc. Set up cam timing to find that original Cam sprocket key way is spot on. Can’t believe it, so checks it couple more times. Its ok! Check it the ‘Esslinger’ way to find it’s a couple a degrees different. We mainly tried it this way to see if their way was credible [later I would set it this way as it is retarding the timing ever so slightly]. Start checking the rocker wear areas etc. to find one rocker is touching retainer, so take this one out and relieve it some more.....much better now. Put the sump on......wont fit. Must use correct pick up with sump.

That's about it, took like 3 months to get this far though!

Some things to consider

If above wasn’t so true it would be funny.

I have talked to other people who have had engines built.
They have also had “experiences”

To lessen this I suggest that you write down what you want done, in detail. Leave one copy with engine and another with boss. Thoroughly discuss each item with boss so that he knows what you require. If he is vague about a particular process or says he will check it out, re-discuss it with him. Communication between workshop owner and machinist is sometimes vague. Generally the machinist is very helpful. Talk to him if possible. Set a positive time frame that both agree with. Keep him to it. Things get lost or forgotten as things drag out. If any one of the above cannot be sorted out prior to starting, move on to another workshop.

Roger Miller




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