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  1. #61
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    Next question....

    Sizing up pushrods for this engine.
    Coming up with 7.950' for ex, 8.100' in.

    Ex in particular some way off what cam supplier expected at 8.150'.

    So begs the questions....

    Head CCs measured 58cc. What sort of numbers are we talking have been milled from the heads?
    And same for meat off the block generally?

    All else being equal, seems this engine's forfeited a total in the realm of .150'.

    Or new valve stems are longer I suppose?

    Next thought, almost certain all valve retainers are same offset (correct terminology?) How can spring pressures be same for ex and in? Perch's would have to be machined deeper/shallower?
    Last edited by COM081; 13-10-2020 at 11:49 PM.

  2. #62
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    Quote Originally Posted by COM081 View Post
    Next question....

    Sizing up pushrods for this engine.
    Coming up with 7.950' for ex, 8.100' in.

    Ex in particular some way off what cam supplier expected at 8.150'.

    So begs the questions....

    Head CCs measured 58cc. What sort of numbers are we talking have been milled from the heads?
    And same for meat off the block generally?

    All else being equal, seems this engine's forfeited a total in the realm of .150'.

    Or new valve stems are longer I suppose?

    Next thought, almost certain all valve retainers are same offset (correct terminology?) How can spring pressures be same for ex and in? Perch's would have to be machined deeper/shallower?
    If I remember correctly .006" off will = 1cc, so you are around .030" to .036" off the heads.

    Valve stem length and seat heights can change the pushrod lengths.

  3. #63
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    You may be close with the .150” being the reason the pushrods are the length they are or it may be way off. Pushrod length falls where it has to to achieve correct contact position and sweep on the valve stem tip. Determining factors include what you stated with machining of surfaces. Other contributors are length of valve, cam base circle, true geometry of the rocker used and even head gasket thickness to name a few.
    Your best bet is to not even concern yourself with what may have happened previously and get a pushrod length checking tool (an adjustable pushrod) and use that to find best contact and sweep. When you find best contact and sweep measure length of adjusting tool and order that length. I have ordered through Crow Cams before.

  4. #64
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    Yeah that's all done, Q, except ordering of pushrods. Just interested really in how much comes off these heads/blocks generally. Learning as I go.

    Thanks fellas.

  5. #65
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    Quote Originally Posted by COM081 View Post
    Yeah that's all done, Q, except ordering of pushrods. Just interested really in how much comes off these heads/blocks generally. Learning as I go.

    Thanks fellas.
    Sorry, interpreted 7.950" and 8.100" as what you already had. Not sure what you mean on your last thought. Do you have different spring installed heights?

  6. #66
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    Haven't read the previous pages, but different brand rockers can affect p/rod length.

  7. #67
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    Sorry, could have been clearer...

    In and ex pushrod lengths are different because valve stems are at different heights (ex sit higher). Retainers are all -.050'.

    May be wrong but I assume installed pressures (and therefore heights) need to be the equal.

    So for the springs to be at equal installed heights, the perches for the inlet must have been machined lower than the exhaust? And this must be the result of how the new valves sit in the newly cut seats?

    Novice question.

  8. #68
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    Quote Originally Posted by COM081 View Post
    Sorry, could have been clearer...

    In and ex pushrod lengths are different because valve stems are at different heights (ex sit higher). Retainers are all -.050'.

    May be wrong but I assume installed pressures (and therefore heights) need to be the equal.

    So for the springs to be at equal installed heights, the perches for the inlet must have been machined lower than the exhaust? And this must be the result of how the new valves sit in the newly cut seats?

    Novice question.
    Or shims installed under the exhaust side springs. Invoice for head work itemized and listing shims and/or machine spring seats?

  9. #69
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    No shims. I know spring seats were machined but invoice doesn't itemise or detail the work. No problem, I'm confident it's right and can just have machinist confirm if need be. Just curious for my own understanding.

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    Did you get the valves replaced ?

    You may find the collet/lock groove is in a slightly different spot on the exhaust valves compared to the intake.

  11. #71
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    Yeah struggler, new larger valves.

    So inlet valve seats machined lower to accomodate lower groove?

    Cheers.

  12. #72
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    Quote Originally Posted by COM081 View Post
    Yeah struggler, new larger valves.

    So inlet valve seats machined lower to accomodate lower groove?

    Cheers.
    Possibly.

    The lock groove height is just one of those things that seems to move around a bit.

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