Possible problems running oversize valves, 472 peanut relief pistons, MTS #15, Potter rockers.

Discussion in 'Big Block Cadillacs' started by DevilDeVille, Jun 13, 2018.

  1. DevilDeVille

    DevilDeVille Active Member

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    As expected, factory HEI is not on par with MTS#15 and roller rockers. Fair enough, we have the MSD dizzy, SS coil and 6AL2 waiting.
     
  2. Darius

    Darius Well-Known Member

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    Wondering how the limits displayed themselves??

    bro. d
     
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  3. 5one9

    5one9 Active Member

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    Having a new MSD distributor in ones possession has that effect on a stock HEI.
     
  4. Darius

    Darius Well-Known Member

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    Point made, point taken.

    IF I had a new MSD distributor in my possession it too would grace my engine.

    Best,

    bro. d
     
  5. DevilDeVille

    DevilDeVille Active Member

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    HEI was dead, as we found out the hard way. Sent out wrong signal to tach and not enough spark at high rpm-s. Took another factory HEI from limo and tach signal was ok, also went up in the rpm range. Just so, that bent 4 pushrods. Mechanic said, that valves are ok. but need to check with inspection camera just to be sure. New pushrods ordered from US and should be delivered to my doorstep by Oct. 22nd. Fingers crossed that it is not piston meet valve situation... Otherwise my 10K euro engine will get a lot pricier.

    [​IMG]
     
  6. DevilDeVille

    DevilDeVille Active Member

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  7. 5one9

    5one9 Active Member

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    Bent pushrods on the engine stand?
     
  8. DevilDeVille

    DevilDeVille Active Member

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  9. Darius

    Darius Well-Known Member

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    Love that sound!!!

    That said, you don't believe in slowly ramping up engine speed, do you? :(

    Well, there is something to the thought that it is better to find any weakness now, than later.

    Best,

    bro. d
     
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  10. 48Austin

    48Austin Safty First! Then pull the trigger!

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    Top Fuel or old Hot Rodders mentality, IT GOES OR BLOWS. Also some.. I'll shut up.;):devil::rolleyes:
     
  11. 5one9

    5one9 Active Member

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    I'm pretty sure I see how you bent the pushrods. I'll also admit to being a 'it goes or it blows' person. I mean really, how many people do you think are breaking in a new Hellcat by the old standards (no synthetic oil and 500 miles of easy driving)?

    I'm seriously concerned about those valves! Keep us posted
     
  12. Cadillac Kid 1

    Cadillac Kid 1 Well-Known Member

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    I just re read the whole thread. Are you using solid lifters with an MTS# 15 cam?
    Greg Surfas
     
  13. DevilDeVille

    DevilDeVille Active Member

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    Nope, hydraulic ones.
     
  14. 5one9

    5one9 Active Member

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    Whew. Did you say what seat pressure you were running?
     
  15. 48Austin

    48Austin Safty First! Then pull the trigger!

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    Just wish Cadman was back! Seems to know ALOT on what these engines need in the cam department! I need to know what might be a good grind for a blower. I remember him saying that these engines like ALOT of lift.
     
    Last edited: Oct 19, 2019
  16. DevilDeVille

    DevilDeVille Active Member

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  17. 5one9

    5one9 Active Member

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  18. Caddylackn

    Caddylackn Member

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    From the Ebay link on your springs, the coil bind height was 1.15", the open height was 1.25", and installed height was 1.70". Does this mean that there is coil bind at only 0.55" of lift at the valve? Am I reading this correctly?

    The old MTS site has the MTS-15 as 0.540"lift for the exhaust and 0.520" lift on intake, this is pretty dang close to coil bind with stock rocker ratios. What ratio are you using again?
     
  19. 5one9

    5one9 Active Member

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    Or if you installed them at 1.86" you'd have no seat pressure, no rpm, valve float, and likely piston to valve contact...……………...even on an engine stand. I hope neither of these things happened, but struggle to believe that the springs were shimmed 0.150-0.200" to obtain installed height.
     
  20. DevilDeVille

    DevilDeVille Active Member

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    Rockers are 1.7:1 i will try to measure installed height of springs tomorrow. No shims and shown springs are just guesswork on my side - purchased the heads complete from ebay some years ago. No specs other than these of valve diameters and head numbers. My machinist tested the springs and valve guides in comparison what the supposed lift should be and they cleared prior to assembly of the engine.
     
    Last edited: Oct 22, 2019

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