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Thread: Pinto Valve Geometry

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    Pinto Valve Geometry

    Seeing as I have the engine out to do various things I decided to measure the valve lift I am getting and to check the rocker geometry. This engine has done 3 tarmac rallies since being rebuilt and has run faultlessly. I have just relied on the engine builder doing the right thing up till now.

    Measuring the lift with the gauge resting on top of the spring retainer;

    Cylinder
    Inlet Lift
    Exhaust Lift
    1
    11.42
    12.04
    2
    11.54
    12.09
    3
    11.78
    12.15
    4
    11.65
    11.85


    The Kent Cams website shows that for a GTS4 cam I should have 13.69mm inlet and 13.36 exhaust. I am missing out on 2mm inlet lift! Q: I am led to believe that stated cam figures are often not achieved so do mine look ok? Me thinks they are a little low. Q: Is there likely to be power lost here? I cannot visually ID any wear in the cam or rockers.

    Next I looked at the rocker position. I made up some gauges as per the Des Hammill book but cannot use them as the cam lobe is wider than the rocker meaning I cannot get the gauge to sit in a useful position. Re-reading Hammill book it seems I have to remove the camshaft thrust plate and move to cam backwards 5mm. It also seems to suggest that checking geometry is done with only 1 rocker in place at a time. My head is currently complete and I didn't really want to take it apart unless I ID an issue. Q: Can I do these checks with it complete? Q: Can I remove the thrust plate with it complete? This is a learning exercise for me but the water is getting deep!!

    Q: As a check of my understanding, the rocker adjusting post ONLY changes the cam to rocker clearance at zero lift (what is than value?)? Q: To change the rocker position (if it is wrong) I have to use lash caps on the valve stem? Q: Are lash caps available in various thicknesses off the shelf? Q: Does the rocker geometry effect lift?

    Kent Cams rockers and valve keepers. Crow Cams dual valve springs. GTS4 cam. Group 1 stainless steel valves.

    Sorry for all the questions...........
    Last edited by MK1_Oz; 01-07-2017 at 08:57.
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    Re: Pinto Valve Geometry

    The first thing to do before getting too concerned is to check that your dti gauge is calibrated correctly and is giving an accurate reading. I had one of the chinkie digital gauges that lead me a dance when rebuilding a Volvo Truck diff. An old British built gauge of 40 odd years vintage came to the rescue.

    2mm does seem a lot of lift to be loosing. Sometimes it's very difficult to get the desired lift that that's listed in the cam manufacturers catalogue how ever hard we try. What length are your valves and at what angle are the rockers running at when looked at from the end view? Lash caps normally reduce lift and not increase it as do long valves.

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    Re: Pinto Valve Geometry

    Will have the head off the car maybe tomorrow so can measure the valves. It is a new chinese DTI gauge that to be honest I have not checked. I will now......

    Sometimes I think I would be better keeping my head i the sand and not learning/looking into things.......
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    Re: Pinto Valve Geometry

    From what I could see of the rocker, it does appear to be a little out from the gauge I made. Will investigate more tomorrow once I work out how/if I can take the thrust plate out so I can move the camshaft.
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    Re: Pinto Valve Geometry

    You can do a quick check. Put the head on a flat horizontal surface. Check the flat side of the follower is also in horizontal position. This is the side where the spring is attached. If this is also horizontal, follower position is ok.

    Most cam grinders will advertise with a max full lift setting more as 1 mm from what ever is possible. Maybe with zero valve clearance but even than. Well, cam grinders always give a total spec. list in the catalogue and never ever one number is correct (except from the price). My experience is that if you buy 2 times the same camshaft you seldom receive the same camshaft. Specially if you ask for other lobe centers. At least for Pinto's. When you switch to cams like Kent or any other flat follower the errors are a lot less.

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    Re: Pinto Valve Geometry

    What valves are you using...wrong length valves alter the rocker geometry..which alters the lift....it would seem the inlet valves are prob over length.....from memory long valves = lower lift..and .shorter valves = higher lift...maybe some one will confirm ...cheers mark

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    Re: Pinto Valve Geometry

    When I bought the head years ago I was told it was Group 1 stainless valves. Other than than they are of unknown origin. Yes I think longer valve = less lift.

    Will do the above check and measure the valve length hopefully tomorrow.

    Not sure if 1-2mm max lift reduction will result in less power?
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    Re: Pinto Valve Geometry

    if you think about it... 2mm is about 15% down on lift...15% is a big number when it comes to the last available power...but the engine will still run well..maybe it could run even better...cheers mark

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    Re: Pinto Valve Geometry

    It is not only the lost in lift which will cost you power, more the rest of the valve timing shape will lower your power.

    Long valves are indeed less lift. Group one valves should be used with much smaller camshaft base circle. Almost impossible to make the stem short enough. You usual end up with the follower tip against the retainers (even with standard valve length).

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    Re: Pinto Valve Geometry

    i agree, group one valves will be way too long, BUT you might not loose as much power as you think, total lift will be down, but IF the head doesnt flow that well at high lift it might not be such a dissadvantage, also the engine isnt at full lift very long. dave walker always said all you really need from a pinto for power is 475 thou (12mm) lift. the other benefit might be reduced lift on overlap, which is a good thing if the cam is a bit ott
    Last edited by Graham; 01-07-2017 at 19:38.

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    Re: Pinto Valve Geometry

    Totally correct Graham. Power comes out of the head, little to do with the camshaft. In one of my tests I've used RL31, Piper A8 and HT1e camshaft. Minimum power was 189 Bhp (RL31) and max Power 193 Bhp with HT1e and A8 but with HT1e 500 RPM later and was almost 1000 RPM later as top power from RL31. I did made the engine rev higher in the same gear, something not possible with RL31 which stopped to rev little over max power. The same RL31 made only 165 Bhp in a head prepared by a Holland Pinto specialist (???) and the same cam did not even made much over 150 Bhp in one other heads I've bought as a test head.

    Indeed, lucky most cams do not lift what they advertise, little over 12 mm has not much of advance. But still there is a difference between a camshaft making 12mm and correct installed and one only making 12mm because incorrect rocker geometric. Timing of the lobes, lift at TDC etc have a big influence on the total picture of power and torque, not just max lift and camshaft duration.

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    Re: Pinto Valve Geometry

    Does incorrect geometry cost/make power or is it mainly concerned with reliability/wear?

    Assuming my valves do indeed measure to be too long, what are the options?
    1. Buy new shorter valves (are these available?)
      Buy new camshaft with smaller base circle allowing correct geometry (currently GTS4 so what would have the right BC?)
      Leave it as it is - possible power loss due to lift, doesn't appear to have any wear issues
      Install new valve inserts and have the valve seats not cut as deep (no idea if this is a possibility!)

    This engine is supposed to be high end and I am looking for every last HP (within reason - there is no endless stream of cash!).

    This is what I found today when measuring the valve clearances;

    Cylinder Inlet Exhaust
    1 0.178 0.203
    2 0.178 0.229
    3 0.178 0.254
    4 0.178 0.279

    Strange that all the inlets are 1 feeler gauge under the required and that the exhausts are all over the place. Cannot see that it is operator error. Will these need changing? Is this a super critical measurement?

    As for the geometry -

    First pic is #1 Inlet which you can see is out by a reasonable amount. The second pic is #2 Inlet which is out by a fraction. #3 and #4 are close to spot on. I have no idea why #1 is different??? Maybe the valve seat is cut depper making the valve tip higher? Didn't look at exhaists yet as ran out of time.



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    Re: Pinto Valve Geometry

    OK just reading more on geometry and valve length. When measuring the valve length, exactly what am I measuring?? Put it head down on a bench and measure the height of the tip above the bench? From somewhere on the valve seat up to the tip?

    I want to learn. I want to improve my engine. I am treading very carefully as I don't want to turn an engine that works well into a dud by stuffing things up!!! Appreciate your help and support....
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    Re: Pinto Valve Geometry

    Despite the Pinto engine been one of the most simplest of engines the valve train geometry is one of the most difficult to get set correctly. It might be worth you checking what the Lobe centre angle is. A timing disc on the cam wheel and measure degrees from full open exhaust to full open inlet. The GTS4 cam should work best close to 106 degrees.

    The total length of the valve is best measured with a pair of vernier calipers from base to tip. The ideal length is the same as what a std pinto valve is.

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    Re: Pinto Valve Geometry

    110mm?
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    Re: Pinto Valve Geometry

    yes 110 mm on valve length, looking at photos you have alot of space between retainer and follower you may just need to tip valves i took 1.5 mm off my group 1 valves cheers mario.

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    Re: Pinto Valve Geometry

    what size carbys do you run and choke size cheers mario.

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    Re: Pinto Valve Geometry

    it should be noted that std valves have very thick faces, this makes them appear long, but the engine only see the valve length as being from seat to tip of valve,

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    Re: Pinto Valve Geometry

    Quote Originally Posted by Forest_rallying View Post
    The total length of the valve is best measured with a pair of vernier calipers from base to tip. The ideal length is the same as what a std pinto valve is.
    Quote Originally Posted by Graham
    it should be noted that std valves have very thick faces, this makes them appear long, but the engine only see the valve length as being from seat to tip of valve
    OK so looks like it is best to actually measure from seat to tip and compare to the same measurement on a standard valve (I have 3 old heads that will have std valves for comparison which hopefully will not have had too much worn off the stem). How do I factor in the position/depth of the valve seat in the head? Until I remove a valve I cannot tell if it is recessed into the head by much. A recessed seat will give a "longer" valve length I believe and must therefore be factored in.

    I think I may order a set of Kent Cams CF36 followers. Reading other threads it appears that these have a long pad but are otherwise like the standard Ford items. The research done by 'RWD Fords Rule' seems to indicate that these do not lose lift like the newer long pad followers. I am going to map the valve lift curves of the current followers then compare to the CF36 folloowers. This hopefully gets a little lift back before I have even looked at the valve length. Looks like I am committing to getting this head geometry spot on!!!!!

    Keep the input coming as I am learning so much as I hope others are......
    Last edited by MK1_Oz; 03-07-2017 at 09:47.
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    Re: Pinto Valve Geometry

    Just heard from Kent Cams. The GTS4 kit apparently comes with the CF36 followers. I can only assume they are still on the car as this head was bought 2nd hand. Can anybody ID them from the pics?
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    Re: Pinto Valve Geometry

    Funny, you are going to do a lot of work, having the lift for all valve correct but have zero control over what is really important. Going to measure valve lengths from seat etc.. all zero advance. No sense at all.

    Make the valve stem so the follower incl. valve clearance is horizontal with the head where the ball stud is (spring side). Most easy is to start with softer springs. Make the stem shorter. If you think you end to short, use a dummy valve. Once you got the right length you can check from valve spring seat to top what you need. If not possible to make them so short, use a cam with smaller base circle and add to the valve stem. Doing so you got the followers spot on whatever valve lift you will get. Should now be right for al in and exhaust valves (can have different max lift).

    About using other followers for more lift or whatever. Stick with the follower the cam grinder was using for this cam. Some use Kent CF36 to increase lift on a Piper cam or any cam. But there is more happening when you do so. Sometimes acc. get critical. If for example, if Piper would need more lift they would have done it with there shape of followers. Dangerous to do this without further knowledge. Cam and follower must match.

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    Re: Pinto Valve Geometry

    The Kent Cams kit is supposed to have their CF36 follower. They sent me a picture of their various types and I currently have the wrong followers. Putting the CF36's in correct this. I don't have a spare valve to grind away in order to get the correct height as you suggest so have to rely on measurement. At the end of the day I have to stick to the valve lengths that are available for purchase anyway.
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    Re: Pinto Valve Geometry

    I can hardly believe the CF36 will correct so much, more PR bullsh*t. They are not that magic.

    If you don't have a valve to cut, make a dummy in a lat 8MM stem and a disc welded is al what is needed. Does not matters how it looks like in the chamber, and valve seat. All we need is the length of the valve stem from valve seat to top. Than measure you can correct the valve so far or need a smaller base circle.

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    Re: Pinto Valve Geometry

    Be carefull if shortening your valves ..some have stellite tips..which is just a hard top layer..so not very thick....cheers mark

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    Re: Pinto Valve Geometry

    Correct an you quickly find out shorting will usual mean follower in contact with valve spring retainer. Smaller base circle is the solution but can also mean more wear if you go to small.

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    Re: Pinto Valve Geometry

    Excuse me for been a bit ignorant, but theoretically if valve lengths are the same on all heads which they should be give or take a couple of thou ( before people start putting the wrong length valves in, ie group 1 which I believe are app 1mm longer shouldn't all base circles on cams be the same ? The mounting of cam never changes, valve length shouldn't change unless someone cuts the seats over deep. So the way I understand the base circle has no need to change ? How do you know or specify a smaller base circle to get over longer valves ? Or am I barking up the wrong tree or is my interpretation of the base circle of a cam wrong ?

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    Re: Pinto Valve Geometry

    a "re-profiled " cam would have a smaller base circle to increase lift.

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    Re: Pinto Valve Geometry

    Almost all cams are grind at standard base circle. Problem is, this is only good with standard valves and even then they are usual not 100%. Valves wear in the head.

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    Re: Pinto Valve Geometry

    Quote Originally Posted by alladdin View Post
    a "re-profiled " cam would have a smaller base circle to increase lift.
    So on that theory you could be be defeating the the object of putting a high lift cam in by possibly screwing the whole geometry up?

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    Re: Pinto Valve Geometry

    Not many company's re-profile Pinto cams. They start from a blank. These blanks can be chilled cast and better quality. And grind to original base circle when needed.

    It is always very easy to screw up a Pinto camshaft setup. That's why so many fail making good power and often the reason why the cam only last a few minutes or one race.

    It's not only the case of a Pinto. Porsche 911 is an other example, only, the guy's working on these engines are so stupid they not even know what valve geometric is. Lobe centers on Porsches can change very quickly and valve profile can be way out from what was the intention to be when they regrind a camshaft.

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    Re: Pinto Valve Geometry

    Had a bit of a tinker in the shed today. I made a 350mm diameter degree wheel using some sheet steel and a printed degree wheel. Works nice. Using my existing cam, followers and clearances, I created a valve lift map for the inlet and exhaust on #1;




    Should be pretty accurate. I swapped the DTI for a mechanical gauge (also chinese shite) to double check the opening and closing points so fairly happy. I intend to do the same with the finished head to see how the areas under the curve compare. More area = more potential flow.

    Question: The Kent GTS4 cam is listed as having 312 degrees duration. My inlet opens 308 ATDC and closes 632 ATDC. This means 324 degrees duration. The exhaust opens at 112 and closes 426 meaning 314 degrees duration. The exhaust is close to specs and the difference could easily be my measuring skills but the inlet is way out. Given these values are effectively ground into the cam lobes I cannot explain the difference. Thoughts?

    Also, the cam card shows timing of 53/79 89/43. What exactly does this mean? I cannot make it match up to my figures. Need help!
    Last edited by MK1_Oz; 05-07-2017 at 12:42.
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    Re: Pinto Valve Geometry

    Glenn,
    first of all can you post the photo you got from Kent Cams with the different types of followers?
    About camtiming: the listed camtiming for Kent Cams is with a 0.25 mm checking height probably this means valve lift. You probably measured the basetiming i.e. 0 mm lift.
    53/79 means the inlet opens 53 degrees BTDC and closes 79 degrees ABDC.
    89/43 means the exhaust opens 89 degrees BBDC and closes 43 degrees ATDC.
    53 + 79 + 180 = 312 degrees duration. 43 + 53 = 96 degrees overlap.
    These are all crankshaft degrees.

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    Re: Pinto Valve Geometry

    A picture tells more than a 1000 words:

    1 = ballstud pivot point of follower
    2 = camshaft
    3 = contact point between cam and follower
    4 = top of valve
    5 = valve (centre line)

    The rocker ratio = (distance between 1 and 4) / (distance between 1 and 3).

    Now when you use a longer valve the ballstud will have to come down to get the nominal valve clearance.
    Point 1 now is lower than before so distance between 1 and 3 is bigger -> lower rocker ratio -> lower valve lift.
    To compensate a longer valve you could use a cam with a smaller base circle; ball stud (1) is now higher again as you set the nominal valve clearance. Restoring the original rocker ratio. But you would need longer ballstuds otherwise you run out of thread which holds these in the head.

    I've seen lots of different followers including the dreadfull Newman items with steel inserts on the contact area and Kent Cams items which were softer than jelly pudding. Original Ford items are better if not the best.

    Regards, Leon.

    Last edited by Miniliteman; 05-07-2017 at 12:57.

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    Re: Pinto Valve Geometry

    Will post the follower pic in the morning when i get home from work. Thank you do much for that explanation of valve height effecting lift. Is now so much clearer.
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    Re: Pinto Valve Geometry

    Hi your figures are not million miles away..just measured different...as miniliteman says ...53/79....or as you have measured would be 307/619...so you can see your not far out 1 degree out on opening and 13 out on closing.. cheers mark

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    Re: Pinto Valve Geometry

    Just done a quick calc on exhaust timings...and i think if my maths are correct your cam is reading; inlet ..52/92. and exhaust 91/66.. this is more like a rc31 cams spec they are inlet 53/90 and exhaust 96/60.....

    cheers mark

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    Re: Pinto Valve Geometry

    Whatever the profile is, if you got over 4 mm at TDC and only making 12mm full lift, will be pretty sad engine.

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    Re: Pinto Valve Geometry

    Quote Originally Posted by madragon199 View Post
    Just done a quick calc on exhaust timings...and i think if my maths are correct your cam is reading; inlet ..52/92. and exhaust 91/66.. this is more like a rc31 cams spec they are inlet 53/90 and exhaust 96/60.....

    cheers mark
    TBH I have always relied on the previous owner as far as what cam is in it. Never looked (I assume Kent would stamp the end of the cam). Will take a peek.

    ...will be pretty sad engine
    It seems to go hard but maybe there is more. Made 167RWHP in this configuration which I guess is around 190HP at flywheel?

    Kent Cams followers as promised;

    1970 Mk1 Escort Tarmac Rally Car

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    Re: Pinto Valve Geometry

    Quote Originally Posted by MK1_Oz View Post
    TBH I have always relied on the previous owner as far as what cam is in it. Never looked (I assume Kent would stamp the end of the cam). Will take a peek.



    It seems to go hard but maybe there is more. Made 167RWHP in this configuration which I guess is around 190HP at flywheel?

    Kent Cams followers as promised;

    hi mk 1 any inlet port photos while head is off i like to compare with my head cheers mario.

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    Re: Pinto Valve Geometry

    Just looked and def a GTS4.

    I really cannot understand how I could be 1 degree out on inlet opening but 13 out of closing!!! Looking at the raw data I had 0.00mm at 306 then 0.01mm at 308 (I worked in 2 degree increments) so pretty much spot on. There appeared to be some drift in the zero point of the DTI but I checked the closing point with a mechanical gauge so am reasonably confident that my closing of 630-631 is what I actually have. Camshaft wear would cause it to close earlier. Given the opening point, the camshaft has not been installed with any/much advance or retard. My clearances on #1 inlet are 0.022mm too tight. Allowing for a follower ratio of 1.5 (guess) that gives valve lift of 0.033mm. Adjusting this off my closing point still gives about 627 degrees so even that is not the answer.

    Also, how can the exhaust be off 21 on opening and 23 on closing? Suppose it must be a measurement issue....

    What an interesting thing is valve geometry!!!!
    1970 Mk1 Escort Tarmac Rally Car

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