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Thread: Pinto valve geometry question

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    World Champion Decade Plus User Pitstop's Avatar

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    Question Pinto valve geometry question

    Right, I'm building up my big valve head and I'm fitting my FR32 cam kit from my old head. As it was bought as a kit and has only covered about 500 miles I am changing the whole kit - cam, followers, posts and I'm keeping them in the order they have bedded in to. The only thing that came in the kit that I'm not changing are the new valve springs because the BV head has double springs - or should I change them for the single Kent ones?

    The first thing I have noticed is that to get the correct valve clearances, all the follower posts needed to be screwed in much further than they were in my old head, 3-4 threads more in fact and most of them now have only 3-4 threads visible. I am assuming this is because the valves in my new head are longer and therefore protrude higher than the other valves did in my old head.

    I have read that longer valves can upset the valve geometry and give a shorter valve lift - is that right?

    What should the actual valve lift be when using a FR32 cam kit? I'm sure I read somewhere that it was around the 11mm mark. In any case, whatever it should be, they should all be the same, shouldn't they?

    I havent got round to measuring the exhaust valve lift yet but these are the lift measurements for the inlet valves:
    No1 9.84mm
    No2 10.57mm
    No3 9.81mm
    No4 10.12mm

    What should the actual valve lifts be? Do the exhaust and inlet valves have the same lift?

    There's obviously something up there so how do I correct it? Is it a matter of grinding/filing the tops of the valve stems or the bottoms of the followers a bit at a time and re-checking the lift?


    Thanks in advance

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    Re: Pinto valve geometry question

    current catalogs state 11.22mm in lift and 10.94 ex, BUT if you cam is quite old you might not get that much lift anyway as kent have increased the lift.

    now all the inlet should have the same lift, the fact they dont is either one or a combination of two things, the valve seats in the head are all at different heights or the followers vary in diamention, try swapping the followers around to see if you can even things up, in reality few engines have exactly the same lift on all valves its only the lift on no2 that really stands out.

    as for correcting it, you cant grind the followers, you might be able to shorten the valves, but that depends on what they are made of and whether your prepaired to risk the valve tips wearing.

    to gain 1mm valve lift you need to shorten the valves by about 3mm, if you dont want to shorten the valves your going to have to buy a new shorter set, or get a cam which has a smaller base circle

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    Racer Decade Plus User RWD fords rule's Avatar

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    Re: Pinto valve geometry question

    Yeah the valves are too long, however different rocker shapes can totally change the valve lift, if they are the long pad rockers which I suspect they are, swop them for the older shape rockers, you usually gain about 0.3 to 0.5mm lift and sometimes a lot more depending on the rockers you have.

    Try fitting no2 inlet rocker in all the other inlets and check the lift, the figures should be a lot closer, this would tell you wether or not most of the problem is with the rockers.

    If you get 10.6mm or so on all valves don't worry about it, it's not going to make much of a difference in a fast road engine unless you want every last bhp.

    Regards
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    Re: Pinto valve geometry question

    Graham:
    The cam kit is no more than two years old so I don't know if that is classed as one of the newer ones with increased lift. I spent a couple of hundred quid on and its hardly used it so I'd like to get some more mileage from it, if at all possible. I'll try swapping rockers around first to see if that makes any difference but I don't mind grinding the valves tips down (just re-read your 'dave' rebuild thread so it looks like a shortening of the valves could be my best option) but when you say that depends on whether I am prepared for the tips wearing, what sort of timescales are you referring to - how long will they last? I will probably only be doing 500 - 1000 miles per year maximum anyway, will they wear out that quickly?

    Jason:
    When you say change them for the older type rockers, I have some fatter looking ones, marked 'camtec'. Are they the older type?

    Both/either:
    What can I use to shorten the valve lengths - grindstone/belt sander/file?

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    Re: Pinto valve geometry question

    re shortening valves, to a certain extent it depends on what they are made of, if they are magnetic they can be hardened simply shorten the valves heat the tips to cherry red and qwench in water, salt water will make them even harder, there is a theretical risk that doing so will make the valves brittle and they might fail at the cotter grooves, but in my view thats not a risk in a fast road engine last time i asked dave he said he'd done about 10,000 miles on his engine with shortened valves,

    most big valves are stainless and cannot be hardened and often have stellite tips, shortening them will shorten there life as your grind through the hard stelitte, as for how much shorter i wouldnt like to say but for 500-1000 miles a year i wouldnt be concerned, at the worst they wil wear and your end up replacing the valves in ime, but right now your only options are leave the valves to long, shorten them or buy new ones,

    you can shorten valves on a belt sander or grinder, the difficult thing is holding the valves square so there tips stay at 90 degrees to the stem, i personally hold the valves in the tool post of my lathe fit a grind stone in the chuck which means i can accuratly shorten them,

    your best bet is probably to get your local engine reconditioners to do it, i would of thought that £20 cash would cover it, just work out how much you need off them, rule of thumb is remove 3 times however much you want to change the lift by
    Last edited by Graham; 04-02-2010 at 23:28.

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    Re: Pinto valve geometry question

    Here is the older original shape rockers which make more lift than long pad types, you should try fitting some of those rockers and see what effect they have on the lift, however only use them if they are new.
    If you do shorten the valves take a little off at a time, make sure you blue the rockers and make sure the cam does not run off the rocker pad.


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    World Champion Decade Plus User Pitstop's Avatar

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    Re: Pinto valve geometry question

    So far, so bad!

    Started on number 1 inlet. After making up a guide and using a brand new grinding wheel, I shortened the valve slightly and removed a bit from underneath the rocker arm where it was touching on the valve cap, rechecked it and had 10.62mm. Great, I thought, just a little bit more and try to get it to 11.22 so I removed more from the valve which meant I had to remove more from the rocker. BOLLOX!!! I took too much off both and there's not enough meat left on the rocker to prevent it slipping sideways off the valve.

    Good job we're only 25 mins from Burtons so I've sent my office lady down to get me another valve and rocker.

    I'll take my time in future.

    I hope this head job doesn't end up like that Jono bloke when he attempted to modify a pinto head.
    Last edited by Pitstop; 05-02-2010 at 14:30.

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    Re: Pinto valve geometry question

    Fuckup number 2.
    After fitting the new valve, removing, grinding, removing, grinding etc. I was getting a bit worried that I couldn't get anywhere past 10.42mm lift and I was running out of valve to shorten. Closer inspection revealed that I had an 11 though feeler blade stuck to my 10 thou one giving me a 21 thou gap on the inlet valve.

    Let me tell you, after adjusting the clearance correctly, the lift went up to 10.98mm! That'll do for me. After shortening all the other inlet valves I now have lifts of 10.98, 10.92, 10.72 and 10.85. The rocker posts are all at what I would describe as having the 'right' amount of thread showing too.

    One other thing I discovered - there was no need to remove too much meat from the bottom of the cam followers for them to miss the valve cap, I removed a small amount and then chamferred the outer edges so that they fitted cleanly, without touching, into the valve cap recess.

    Just the exhausts to sort out now before I can go home.

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    Re: Pinto valve geometry question

    All exhausts done and from having between 9.85 and 10.14mm of lift I now have between 10.61 and 10.71mm of lift. I'll leave it at that - should be okay, shouldn't it?

    One more minor balls up - when taking the valves back out I ripped every single one of my modified valve seals. Luckily, the garage over the road hardly ever change valve seals when they fit a head set so I helped myself to a big handfull of valve stem oil seals from their drawers.

    Should I leave the double valve springs on or fit the single ones - as I said, I won't be doing mega mileage in it so there shouldn't be too much strain/wear on the cam & followers should there?

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    Re: Pinto valve geometry question

    i'd fit the singles no point in having more spring pressure than you need, unless your planning on going drifting or doing lots of rolling burnouts where your gonna hold it on the limiter

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    Re: Pinto valve geometry question

    A pic to help?

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    Re: Pinto valve geometry question

    Fit whatever springs are meant to be used with the cam, too much pressure and you will have excessive cam wear plus loose an odd bhp or two due to the increased friction, too little pressure and the valves will bounce at high rpm and if abused will wreck one of these parts or a combination, valve, valve seats, retainer, collects or even break a spring, since your engine is for fast road most of that doesn't apply.

    Check the recommended valve spring installed height and measure all of your spring installed heights, if the spring is not compressed enough then use a shim under the spring to bring it closer to the recommended height.

    Regards
    Jason

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    Re: Pinto valve geometry question

    Quote Originally Posted by RWD fords rule View Post
    Fit whatever springs are meant to be used with the cam.......Check the recommended valve spring installed height and measure all of your spring installed heights, if the spring is not compressed enough then use a shim under the spring to bring it closer to the recommended height.

    Regards
    Jason

    Graham/Jason
    Right, I am now in the process of fitting the original Kent springs that came with the cam. I still have the sticker that came with the kit that states: 'VS9 installed height 1.440"/36.54mm'. I take it that the installed height is measured from the recess in the head and the bottom of the spring retainer cap? Also, if it is too large (which they are at the moment - at 38mm) I add some shims into the recess and then measure again, this time from the top of the shim to the bottom of the spring retainer? In other words, the fitted but uncompressed length of the spring. Is that correct? Also, I'm marking the rocker pad faces (not with eng blue but a spray can!) and checking the pad/cam contact and whilst the marks are not dead centre of the pad, they are nowhere near either edges of the follower face. That's what I should be checking for, correct?

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    Re: Pinto valve geometry question

    Yes you are correct about all you said, the rocker wiping area doesn't have to be in the middle of the rocker pad, just make sure it doesn't come off the end of the pad, if it did the cam would eat itself off the rocker pad edge in a very short time.

    Fit a 1.5mm steel shim or a 1mm and 0.5mm shim, place the thickest shim on top and make sure it is no less than say 0.9mm thick so that is has enough meat in it to allow for wear.
    I bought 1mm shims off burton power last year, just needed the centre hole boring out with a cordless drill and a multi step drillbit, I might be able to find out which shim it was for you.

    Regards
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    Re: Pinto valve geometry question

    What I'm using (again, courtesy of the garage over the road) are the bottoms of the CVH valve stem oil seals:

    Before:


    After:


    I'm cleaning up the rough edges before fitting, but these 'shims' work out at juuuust a tad over 1mm thick so using 2 home-made shims per spring I'm getting an installed height of between just under or just over 36mm. That may slightly increase as the shims and/or the valves settle but I still have in excess of the required 1mm clearance between the coils on full lift so I'm assuming that should be okay - please feel free to let me know if that thinking is wrong.

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    Re: Pinto valve geometry question

    What is the ID of that shim?

    The std pinto head has a spring locator ID of 20.7mm and kent VS42 double springs have a 17.4mm ID, was your head machined to fit kent VS42 springs?
    Make sure the shim ID is a good fit on the head, a little play is fine.
    Last edited by RWD fords rule; 08-02-2010 at 15:00.

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    Re: Pinto valve geometry question

    Shim I.D. is approx 21.7mm and is a nice fit in the recess - there is some sideways play but not enough, for example, for the spring to slip off the shims if they moved to their maximum amount in any direction.


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    Re: Pinto valve geometry question

    Quote Originally Posted by Roger Miller View Post
    A pic to help?

    They look like light gauge springs Roger ?

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