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Thread: Pinto Valve Geometry

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    Re: Pinto Valve Geometry

    hi mk1 oz

    check you wipe area on follower with blue ink it should wipe on the middle of follower
    i send you a private message with my phone number you can call me i help you i did my 2 litre pinto motor cheers mario.

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    Re: Pinto Valve Geometry

    Quote Originally Posted by MK1_Oz View Post
    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!!!!
    I think its prob caused by long valves...cams installed correctly opens at the specified setting (53) then because of the geometry it all goes pear shaped...check an inlet valve length...i notice burtons are now selling "correct" length valves...

    as you say interesting...cheers mark..

    the kent cams follower is oem spec..so it will be interesting to see if this makes any difference...

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    Re: Pinto Valve Geometry

    It's not because you got 190 Bhp it automatic mean you got a good engine. When I say "sad engine" I mean it can work a lot better. Specially in lower revs. Over 4 mm lift at TDC will mean difficult carb tuning and no real power at anything under 3500 - 4000 RPM. You can have and 190 Bhp and low down torque if you reduce the lift at TDC for this valve lift numbers. Anytime no exceptions. Believe me, done it a hundred times at all kind of engines and the trick is always working.

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    Re: Pinto Valve Geometry

    167 Bhp at the wheels was not 190 Bhp on my rolling road, more like 180 - 185 Bhp. As far as the rolling road is calibrated regular

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    Re: Pinto Valve Geometry

    13hp transmission loss.....hmm!

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    Re: Pinto Valve Geometry

    If my calculation is right, if the cam is timed like in your drawing, the inlet is at 110° and exhaust is 91°. Lobe centers are symmetric +/- 100° from center tot TDC.

    If you can make the valve stem length correct you will gain some lift and and reduce the lift at TDC. If the cam was installed this way the engine was probably able to rev very high but I don't think it can make good power over a long range. I'm quite sure about this.

    BTW: very clever to make this drawing. This way you can see what you are doing and compare with next profile of even with next valve data when stem is corrected.

    My advice, make a dummy valve from a simple disc and 8MM rod. Set followers as I suggested and measure again.

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    Re: Pinto Valve Geometry

    Quote Originally Posted by MK1_Oz View Post
    That CF12 looks horrible, like an unfinished CF36 ...

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    Re: Pinto Valve Geometry

    I definitely have more playing to do but probably not for a week. I will report back once I can establish the current valve length and I will see if I can make up a dummy valve to work out the ideal length (or I will just destroy the ones I have then replace them).

    This might be a stupid question so be nice.........when buying replacement valves, do i need to get them machines to suit my existing valve seats or is the valve seat angle always the same and therefore they will just drop in with maybe just a bit of lapping?????
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    Re: Pinto Valve Geometry

    Oh dear Oh dear Oh dear.......... numpty alert

    All of my figures are off by 12 degrees as I set the degree wheel to TDC (0 degrees) at the 12 degree BTDC timing mark. So embarrassed.

    My inlet opens 295, closes 619. The exhaust opens 99, closes 414. Using the correct terminology that means 65/79 81/54 (if my maths is correct). Inlet opens 12 degrees early but closes correctly. Exhaust opens 8 degrees late and closes 9 degrees late.

    Here is the corrected graph;

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    Re: Pinto Valve Geometry

    This might be a stupid question so be nice.........when buying replacement valves, do i need to get them machines to suit my existing valve seats or is the valve seat angle always the same and therefore they will just drop in with maybe just a bit of lapping?????
    bigger valves will have same seat angle. but you will need to get the seat recut to suit the bigger valve diameter, if you were able to lap bigger valves in on existing seats all you would do is loose flow as you would have same size hole but a bigger restriction stuck in it

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    Re: Pinto Valve Geometry

    Quote Originally Posted by MK1_Oz View Post
    Oh dear Oh dear Oh dear.......... numpty alert

    All of my figures are off by 12 degrees as I set the degree wheel to TDC (0 degrees) at the 12 degree BTDC timing mark. So embarrassed.

    My inlet opens 295, closes 619. The exhaust opens 99, closes 414. Using the correct terminology that means 65/79 81/54 (if my maths is correct). Inlet opens 12 degrees early but closes correctly. Exhaust opens 8 degrees late and closes 9 degrees late.

    Here is the corrected graph;

    So looks like..the exhaust valves are correct length..and inlets to long....cheers mark

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    Re: Pinto Valve Geometry

    if you get a minute..could you measure the cf12 and compare to the cf36...from valve contact point to cam contact point,...cheers mark..




    cheers mark

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    Re: Pinto Valve Geometry

    All followers will be approx the same. Everybody is waiting for a miracle but this is not going to happen. These "long pad followers" where long time used by almost every cam grinder. The biggest issue I found was that the contact with the stem is smaller and for this reason faster "eating"' the top of the valve stem.

    OK possible your degree disc was out 12° but LC will not change for lift at TDC, still high compared to the rest.

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    Re: Pinto Valve Geometry

    i always wondered why they didnt just make the valve contact patch deeper...to match the overlength valve..this would retain geometry...i think...hence my question..about measurement....cheers mark

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    Re: Pinto Valve Geometry

    Quote Originally Posted by madragon199 View Post
    i always wondered why they didnt just make the valve contact patch deeper...to match the overlength valve..this would retain geometry...i think...hence my question..about measurement....cheers mark
    On the face of it that is a great suggestion. Why not mill or the follower by amm or so? Must be a reason why this isn't done.

    The new followers won't be with me for a week or so (carrier pigeon union rules i believe) but i will measure when i get them.

    Graham - i was more thinking of the valve seat angle on a new valve of the same diameter but shorter length. From what you say they will have the same angle which makes things easy.
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    Re: Pinto Valve Geometry

    Id imagine they are ground and hardened not milled??

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    Re: Pinto Valve Geometry

    I have totally no idea what would happen if this contact pad would be higher into the follower (ps, they have a radius, are grind and hardened, milling is no option). Maybe something else become a problem, maybe not. Until date using valves as short as physical possible (without touching the spring retainers) and using a smaller base circle is all we can do. 28 mm is a good starting point. It's a gain of little over 1 mm in valve stem length.

    Using shorter valves (in total length) has also draw back because the valve spring will be shorter and more difficult to produce a hight lift long live spring.

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    Re: Pinto Valve Geometry

    Quote Originally Posted by onyd View Post
    Using shorter valves (in total length) has also draw back because the valve spring will be shorter and more difficult to produce a hight lift long live spring.
    Not knowing Pinto's intimately - is there any reason not to sink / cut the spring seats deeper to retain spring length?

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    Re: Pinto Valve Geometry

    Yes you can. In the very beginning of Pinto tuning everybody was cutting the seat for installing Crane springs. But all takes a lot of time and effort. It's totally not impossible to get the valve geo right without doing these things. Just make you valve stem lengths right (don't start with worn out valve seat cut in millimeters into the head, repair with new steel seats before you start messing) and fine tune the rest by having the cam grind to the right base circle.

    The point is, you have to start calculating and measuring BEFORE you order your camshaft etc.... The difference between a good (Pinto) engine and one that produce an average low power engine is usual TIME.

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    Re: Pinto Valve Geometry

    Quote Originally Posted by katana View Post
    Not knowing Pinto's intimately - is there any reason not to sink / cut the spring seats deeper to retain spring length?
    done it many times

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    Re: Pinto Valve Geometry

    Quote Originally Posted by onyd View Post
    The point is, you have to start calculating and measuring BEFORE you order your camshaft etc.... The difference between a good (Pinto) engine and one that produce an average low power engine is usual TIME.
    And experience i'm guessing! If you are upping the valve lift then spring binding and guide contact should be checked and particularly if rev ceiling is raised - seen a few engines that got 'buzzed' with a missed gear change and results in broken springs and followers even though static clearance was good! Yes it takes time but if fitting guides, the head will be jigged anyway so cutting the seats is time saved - springs can be shimmed to regain pressure if required - all part of race prep or is it quiet secrets time? LOL!

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    Re: Pinto Valve Geometry

    Agree it all can be done, lowering seats etc.. but then next problem, finding a suitable shorter valve !!! so you keep facing problems but is normal in tuning. Like all people who build engines on a regular base, it all seldom fit's and this is where you loose the time.

    But without going into redesigning custom made valves and other exotic parts, it's is totally no so difficult to shorten the valve stems and order the right base circle from the very beginning. Can not understand why everybody keep trying to make it any more complicated. Is this the first time ever someone is trying to get the geometric right? This is standard stuff here.

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    Re: Pinto Valve Geometry

    Quote Originally Posted by onyd View Post
    Is this the first time ever someone is trying to get the geometric right? This is standard stuff here.
    First time for me..................
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    Re: Pinto Valve Geometry

    Quote Originally Posted by onyd View Post
    Is this the first time ever someone is trying to get the geometric right? This is standard stuff here.
    First time for me..................
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    Re: Pinto Valve Geometry

    Very good, if you want to do it right in a short time, make that dummy valve. A big round plate (rondel) and an 8 mm rod is al what is needed (or old valve, even one smaller as needed in the seat). Fit a soft spring push it up against the combustion chamber. Now start shortening until you got the follower right (including valve clearance). Follower right is in horizontal position where ball stud / spring is located. This way you will be more than close enough. Measure the length from valve seat to top of stem. Now re-instal you valve and check you can make the top of the stem so much shorter. If you can for example only cut 1 mm and need 2 mm than you need a cam with a base circle 2 mm smaller (1mm x2). Job done. All the rest is making it more complex.

    You can measure this with a standard camshaft BEFORE you order. Once done you measure you base circle and if needed calculate the exact base circle for the new cam. Place your order at a camshaft grinder.

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    Re: Pinto Valve Geometry

    Taken on board. Im not looking to buy a new cam though. .....
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    Re: Pinto Valve Geometry

    I don't know the purpose of your engine but it may certainly be worth considering a modern profile than GTS4 any way.
    Also, you may be resisting to a cam change but how about the cylinder head's port and seat work ? If I didn't miss, you haven't shared the details of your cylinder head yet. Here at TS, there are very knowledgeable friends who might comment and help you if your cylinder head is worth to continue with your rebuild. Sometimes, cylinder heads are beyond the point of correction and your efforts for the best valve geometry may not worth it. Once, you have figured out the correct valve lenght based on the very valuable information on this thread, there are various options including custom ordering your valves from GS valves (UK) and many other US based companies. Burton also has some decent quality valves off the shelf but today almost none of these valves can be shortened from the tip. I have had similar issues when I was trying to get the installed position tip heights dead equal in order to not to have timing variations ( because if the installed heights are somehow different than the timing of each cylinder will change ) and end up ordering different lenght valves from GS.
    Pinto valve geometry can certainly drive you crazy but with all the help which is given at the above posts, I am sure you will be able to get it right.

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    Re: Pinto Valve Geometry

    From the Bhp numbers he gave us (talking about +/- 190 Bhp) his cylinderhead must be spot on (unless the power figures where not measured accurate).

    That's about what you can expect from a very well tuned 2 Ltr. Wondering it is indeed 190 Bhp. For sure, with the cam timing he gave me (very well done that plotting, tells more about a cam than anything else) I'm quite sure, no torque at low RMP and VERY difficult to get the carbs right.

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    Re: Pinto Valve Geometry

    The only thing that could prevent the effort to get the geometry correct on this head would be if the seat were well into the head and even that could be compensated for with shorter valves. There are pics of my head in other threads but may put more on when i finally get time to pull it off.

    A new cam is not better just because it is modern but only if the grind better suits the engine. This is s tarmac really engine and to date the GTS4 had worked well for me. Open to suggestions of other cam grinds. There are probably cams that will give better low down torque. For me to spend more cash on a be can it would need to be a decent level 'better' than i have now......
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    Re: Pinto Valve Geometry

    190 bhp is serious power even for a good spec 44.5 mm inlet valve Pinto without some exotic head modifications like the raised port etc. However, for spot on builds with a really good injection based cylinder head, I guess 190 bhp and littele more is quite achievable.
    Your engine is used for tarmac rally. But is it with long straights or with short straights and many corners ? If it is Long straights type of tarmac rally then your engine may be happy with GTS4 or with similar cams that has a strong top end. HT1 and HT1e is in that family I guess. But, if your tarmac rallies has short straights and many many slow to med corners like us then GTS4 certainly is not the correct cam against the clock. In those environments, wider usable power band and strong mid range seems to be the winner at least for a carburated engine.
    Nevertheless, your aim to get the geometry correct is certainly the correct approach to improve an already performing engine. In my opinion, switching to CF36s and shorter valves will help to a certain extent but trying to reach to the advertised GTS4 lift by changing the geometry radically should not be the option.
    As Onyd mentioned, we never know if the cam is grinded correct at the factory. Unfortunately, I have also seen quite a few out of specs brand new cams during my Pinto builds.

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    Re: Pinto Valve Geometry

    Our tarmac rallies are a mix but more faster stuff. My engine doesn't operate much below 5000rpm though.

    As to whether the dyno the car ran on is accurate we could argue that all day long. No idea. An inaccurate dyno would probably get called out and not given any custom so i will assume it is accurate enough. This engine therefore can be assumed to be making around 190+.

    This is a thread about valve geometry. I don't want it to become about dyno accuracy...
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    Re: Pinto Valve Geometry

    Just found this. Does it look like the valves are quite sunken? Not sure if normal or not;

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    Re: Pinto Valve Geometry

    Nor do I want to start a tread about accurate dyno's but when I see your inlet valve so deep sunken into the head, I guess it was not when you where measuring the power of 190 Bhp?

    But max power does not matter, I had and engine with 193 Bhp and several with 190 Bhp and my Grandma can still use the car for shopping. It's idles like normal, it still pull's very well from 1000 RPM and all comes into action before you see 3000 RPM. That's what I call a good engine.

    Indeed with the cam time like in you drawing you will see a peak of power very high but takes a lot of time to get there. Really with a bit of work you can make this engine a lot better. Put some new seats in the head, get the geometric as good as you can and will already be a lot better.

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    Re: Pinto Valve Geometry

    Just back from a trip away and found 30 minutes of play time. Measuring the CAMSHAFT lift;

    Cylinder
    Inlet Lift
    Exhaust Lift
    1
    8.14
    8.09
    2
    8.10
    8.15
    3
    8.11
    8.19
    4
    8.11
    8.14

    The Kent Cams quoted camshaft life figure is 8.25mm so I am short all round. 0.14mm camshaft lift equates to around 0.24mm valve lift (rough follower measurements 60/35.5=1.69). Accounts for some of my lost valve lift.

    Is it normal for camshaft lift to not equal the quoted lift? I suspect not. Assuming not, does this mean that my camshaft has worn? To check that possibility I ran the DTI gauge on the edge of the camshaft lobe (where the follower does not touch) but only got maybe 0.01mm additional camshaft lift indicating minimal wear.

    Am very interested to hear your opinions of my valve seat depth and whether that is an 'issue' that needs fixing as part of getting the geometry correct.

    Just a little bit more of the puzzle. Few days of work to come them back into the shed.....
    Last edited by MK1_Oz; 10-07-2017 at 10:07.
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    Re: Pinto Valve Geometry

    from reading of other threads and contributions by respected members here i believe you have too much faith in manufacturers supplied data.

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    Re: Pinto Valve Geometry

    Maybe the manufacturers consider them to be within certain tolerances an so feel happy enough to state certain data.

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    Re: Pinto Valve Geometry

    If you cannot believe the stated figured on something you buy from a respected manufacturer then heaven help us!
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    Re: Pinto Valve Geometry

    Just what I always try to explain, don't look at the advertising numbers, they are usual totally incorrect. I've also warned a million times, it is extreme difficult to order 2 times the same camshaft. If I order camshafts (no matter where) I usual have to send 50% back for regrind. No, 50%, not a misprint (cams with followers like Pinto and Porsches are the problem, with direct acting or follower as KENT engines the problem is more like 5%). I'm telling this for a very long time but seems like most people can't read my rubbish English. Or don't want to read (hear) it.

    In this case, they not even managed to make one shaft and 4 the same lobes, let along the timing. Must say, I've measured on some Piper cams and where all the same lobes and lift (or all wrong but the same wrong).

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    Re: Pinto Valve Geometry

    Well i am amazed. For me then it's a case of try to get the most lift from what i have.
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    Re: Pinto Valve Geometry

    Lift and duration sells very well. So you will seldom see what they advertise.

    Lift does not matter to much, as long as you can get the Lobe positions right it is Ok. Start installing the right valve lengths and see what you get (dummy or old Pinto valve will do the job).

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