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  1. #1

    Default GT40P: Pushrods Too SHORT?!

    So, I was attempting to check piston to valve clearance on my new shortblock combined with my GT40P heads that I've had for a while. This is the first time I've mated the two together and the first valvetrain check of any kind I've tried to do. I found a surprising result. My P heads were milled a bit before I bought them for compression. After removing them from my old engine, I had them checked at a machine shop, who also milled them for a smooth mating surface.

    What I have now is, new shortblock, new cam, new lifters, new pedestal roller rocker arms, and same heads. I haven't ordered pushrods yet. I thought, almost for sure, my old pushrods would be too long, what with the heads having been milled as much as they have. Nope. Went to put things together with the old pushrods to do this test, and.... they are too SHORT. I can't even get zero lash. I got the same result with the stock rockers too! How did that happen?! These are the same pushrods I've had since the original '90 302 with E7 heads! Do engine blocks have inconsistent deck heights? The new shortblock is an original block 306 bored .30 over. Oh, and the head gaskets are the same style I used before too. Head is not torqued, but snugged down. I think that's what you normally do when doing the PTV check. Both blocks are roller.

    I'm way confused.

    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI, T-5
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  2. #2

    Default

    Do not feel alone with your confusion, many of us have been there too. Those of us that are married; choose to remain confused, it keeps the wives away.. You are honestly looking at an entirely new motor to include valve train. let go of the past... Psychological trap all conservative motor builders fall into.
    1) My first recommendation is stop, relax and watch this video "atleast twice"... https://www.youtube.com/watch?v=o5is9BsH5OU. You will be smart fallowing it! No insult to your current intelligent level.

    2) Back to the confusion; Looking at your post and photo; first contributing factor as you stated is the fact the heads milled "twice" that brings a fellow fox father a more grave concern is both phases of compression ratio issue you will deal with next. Keep that in mind O.K. Piston to valve clearance is now an issue regardless of the larger P head volume chambers in comparison to aftermarket aluminium heads.

    I am also counting on our fellow Fox daddies to pick up and chime in O.K.

    The photo looks like the factory push rods ?? Toss them or weld them into a cool BBQ grill, I'll bring the Delmonico steaks! Your motor is worth ten times those push rods.
    3) You must accept the fact that you are building a "new" motor and will have to order the correct pushrods. not an expensive endeavor unless you do not do so.

    I strongly recommend spending the few dollars and "invest in your new motor", with the purchase of an adjustable pushrod length push rod tool. Yes, look at your motor with those very good choice Scorpion rockers; that I've spun up to 7500 on a dyno stand with no issue and they asked for more and tell your motor, your worth it baby!

    O.k watch the attached video like..real smart professional on it.
    3) divorce your mind trap of past usage of parts and start a fresh approach., Check everything, lifter position, rocker installation, what shims or bars do I have installed under them, head gasket thickness, and can you check back with your machinist and get the figures on the head deck height (-) or cut from stock. Block deck height figures as well.

    4) mock the heads back up, torque them down and start again with the adjustable push rod , "tool" REGARDLESS of the pushrod company you choose, i.e crane, comp cam, and on and on; all can provide down to the micro length the correct length pushrods you need. If they cannot ..."run". I am certain no fox daddy will challenge that advise!
    5) Unless your scorpions are not installed correctly pedestal or post, you should get the just of my advise and start fresh.

    HANG IN THERE!

    Note: I just finished another 357 build number 3, and this time, the push rod length cam out to be exactly the same length as a stock "Dodge" 318 motor", so you will never know unless you do it right; every build will be different. If anyone on here or in the known universe tells you they can build a bunch of motors and use the same "length" pushrods...run faster.

  3. #3

    Default GT40P: Pushrods Too SHORT?!

    Oh, yeah, I should qualify that i intend to get new pushrods. I just figured that my old ones would work fine to the piston to valve check because, if anything, they would probably be too long.

    I figured the order of valvetrain tests/adjustments would go: piston to vavle, pushrod length, lifter preload, and then rocker arm geometry. After all, if you order pushrods and then piston to valve doesn't go well, because of the ways you might address that, you're probably gonna hafta order pushrods AGAIN.

    I know, this is in essence a new engine, but since they are both factory 302 blocks, how could deck height be a thing that could be inconsistent? You'd think that would complicate the manufacturing process immensely if they'd have to stop and measure for pushrods on every motor. I know some things can be inconsistent and other parts are designed to work with that potential inconsistency, I just didn't think this could be one of them.
    Last edited by ZephyrEFI; 07-09-2019 at 07:36 PM.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI, T-5
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  4. #4

    Default

    Interesting follow, I'm probably a month away from starting a similar journey...with less variables, but still seems like something to learn here.

  5. #5
    FEP Power Member mcb82gt's Avatar
    Join Date
    Jan 2004
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    Olathe, KS
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    1,616

    Default

    Quote Originally Posted by Str8sixfan View Post
    Interesting follow, I'm probably a month away from starting a similar journey...with less variables, but still seems like something to learn here.
    Agreed. Me too.
    Mike

    Now stang-less.

    88 Cougar 5.0

  6. #6

    Default

    Quote Originally Posted by mike357 View Post
    Do not feel alone with your confusion, many of us have been there too. Those of us that are married; choose to remain confused, it keeps the wives away.. You are honestly looking at an entirely new motor to include valve train. let go of the past... Psychological trap all conservative motor builders fall into.
    1) My first recommendation is stop, relax and watch this video "atleast twice"... https://www.youtube.com/watch?v=o5is9BsH5OU. You will be smart fallowing it! No insult to your current intelligent level.

    2) Back to the confusion; Looking at your post and photo; first contributing factor as you stated is the fact the heads milled "twice" that brings a fellow fox father a more grave concern is both phases of compression ratio issue you will deal with next. Keep that in mind O.K. Piston to valve clearance is now an issue regardless of the larger P head volume chambers in comparison to aftermarket aluminium heads.

    I am also counting on our fellow Fox daddies to pick up and chime in O.K.

    The photo looks like the factory push rods ?? Toss them or weld them into a cool BBQ grill, I'll bring the Delmonico steaks! Your motor is worth ten times those push rods.
    3) You must accept the fact that you are building a "new" motor and will have to order the correct pushrods. not an expensive endeavor unless you do not do so.

    I strongly recommend spending the few dollars and "invest in your new motor", with the purchase of an adjustable pushrod length push rod tool. Yes, look at your motor with those very good choice Scorpion rockers; that I've spun up to 7500 on a dyno stand with no issue and they asked for more and tell your motor, your worth it baby!

    O.k watch the attached video like..real smart professional on it.
    3) divorce your mind trap of past usage of parts and start a fresh approach., Check everything, lifter position, rocker installation, what shims or bars do I have installed under them, head gasket thickness, and can you check back with your machinist and get the figures on the head deck height (-) or cut from stock. Block deck height figures as well.

    4) mock the heads back up, torque them down and start again with the adjustable push rod , "tool" REGARDLESS of the pushrod company you choose, i.e crane, comp cam, and on and on; all can provide down to the micro length the correct length pushrods you need. If they cannot ..."run". I am certain no fox daddy will challenge that advise!
    5) Unless your scorpions are not installed correctly pedestal or post, you should get the just of my advise and start fresh.

    HANG IN THERE!

    Note: I just finished another 357 build number 3, and this time, the push rod length cam out to be exactly the same length as a stock "Dodge" 318 motor", so you will never know unless you do it right; every build will be different. If anyone on here or in the known universe tells you they can build a bunch of motors and use the same "length" pushrods...run faster.
    I see what you're getting at. I have definitely made assumptions, and they seem to have no basis in reality.

    That video is certainly informative, but as I don't have stud mount rockers, I can't use his technique. Wait... can I? If I adjust the rocker downward using my bolt and then adding shims to make up the difference so it will tighten... I guess I don't know enough about how you adjust stud mount rockers. I need to do more research.

    Part of the confusion is that right now, the rocker arms tighten all the way to the pedestal with the factory pushrods still VERY loose. There's a good 1/8" of gap there. I know, I know.... assumptions... I need to let go of them.

    It's overwhelming having so many new variables here. But it does seem I have things completely backwards. Rocker geometry first, then pushrod length and so on.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI, T-5
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  7. #7
    FEP Power Member gmatt's Avatar
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    Default

    what is the cam? Was it ground on a smaller base circle?

  8. #8
    FEP Member
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    Default

    With everything being the same except the rocker arms, my guess would be the rocker arms. The pedestals may be taller than the stock type. I have had to cut the bottoms of the pedestals down before, shim them to get them to work out right. Also. if there was a valve job done, and the tips of the valve weren't ground to the right height, there would be a problem there as well.

    The rockers are the one item you didn't have before.

  9. #9

    Default

    Quote Originally Posted by dynodon64 View Post
    With everything being the same except the rocker arms, my guess would be the rocker arms. The pedestals may be taller than the stock type. I have had to cut the bottoms of the pedestals down before, shim them to get them to work out right. Also. if there was a valve job done, and the tips of the valve weren't ground to the right height, there would be a problem there as well.

    The rockers are the one item you didn't have before.
    I did try original rockers and the pushrods are still too short. It's not the same engine block, but they should both be similar model year roller 302 blocks. Valve job has not been done. I only ran these heads for a few hundred miles on the previous engine so there was no need.

    Lifters are the same type, same height, new ones have been soaking in oil for a good month. Also, on the intake valve, I'm using the solid lifter for mockup, so whether or not the lifter is pumped up all the way is not a factor.

    Cam base circle is possible. It's a Flowtech cam intended for GT40 roller motors though.

    I kind of panicked though because I had to imagine I had done something wrong with the assembly to end up with the pushrods being too short. I guess I don't know what that could've been though.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI, T-5
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  10. #10

    Default

    Flowtech says the base circle is a bit smaller, but not like a retrofit cam. That's good enough for me. We're movin' on. I just didn't want to get pushrods having done something wrong and then end up destroying my valvetrain because they were way too long or something.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI, T-5
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

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