Valve to piston clearance ?

Big Block A body Tech

  1. challenger57

    challenger57 cuda57

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    First my motor is 470 stroked 400 with stealth heads and a 586 solid roller comp. cam and 11.00 cr. I put some playdo in the valve reliefs to check clearance and the the intake side was about .300 and exh. was about .400 with 82 cc heads. Does this sound right, if not what is wrong??? Rockers are Hughs bushed with roller tips.
     
  2. DJVCUDA

    DJVCUDA Well-Known Member

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    without knowing alot more information like piston , deck height, gasket thickness and so on it;s not easy to say, but it sounds like you have a friggin mile... you need to be at lease .090 and you got that!
     
  3. IQ52

    IQ52 Well-Known Member

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    Did you rotate the engine over slowly for a few revolutions, with the cam installed and timed?
     
  4. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    X2. What sort of procedure did you use for these measurements? You can not for example, check V/P clearance at TDC. There is a point as the piston comes up, over center, and back down, that valve clearance is actually LESS than at TDC
     
  5. bOb shingler

    bOb shingler Well-Known Member

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    this has to be done as was said in answers 3&4. you're looking for .100" on exhaust and .090" on the intake to be on the safe side.
     
  6. challenger57

    challenger57 cuda57

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    Yes hand cranked it several times. Took it apart and redid it several times just to be sure and came out the same.
     
  7. ramcharger

    ramcharger Dismember

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    Keep in mind that if you are using hydraulic lifters, the springs and clay will push the lifter plungers down to the bottom of the lifter bore giving you a false reading. The correct way to do this is with a light checking spring and a dial indicator on the valve retainer.
     
  8. DJVCUDA

    DJVCUDA Well-Known Member

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    he said it was a solid roller fyi
     
  9. moper

    moper FABO Gold Member FABO Gold Member

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    So long as you rotated it a few times it sounds fine. That clearance depends on the piston, the deck height, the cam, the sizes of the valves, the head, and the head gasket. So there's not much for a specific number to shoot for... Just don't let them get too tight as Bob said.
     
  10. greymouser7

    greymouser7 Vagrant Vagabond “Veni Vidi Vici” FABO Gold Member

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    how much stretch is there in the valve train when it heats up?

    When Jim/IQ52 competed in the engine masters Mopar muscle challenge, this other guy with a 361 had his valve hit his 361 piston and blow up the motor. I assume that he did a valve to piston check...? is this limit pushed with these kind of builds?
     
  11. IQ52

    IQ52 Well-Known Member

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    The 361. Somebody there just made a big mistake, all eight exhaust valves were hitting the top of the cylinder walls/deck....small bore/big exhaust valve. They said they had checked all the clearances. #2 exhaust valve was the first to break and shut the engine down. You could look into the exhaust port and see the camshaft.

    Our 451 engine, two years before, had .052" piston to valve clearance on the intake and .068" clearance on the exhaust. We had no problem spinning it to 7600 rpm, but, I'd like to think that was because we know what we are doing. Its important to be smarter than your cylinder heads.
     
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    • william

      william Well-Known Member

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      If I recall it didn't hit the piston it was clipping the cylinder wall ,the 361 has a small bore at 4.12" compared to a 400 at 4.34
       
    • ramcharger

      ramcharger Dismember

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      Please re-read my post. I started with "Keep in mind that IF..." I posted that as a benefit to those that read this thread so they don't make a costly mistake. Having the whole story and complete information is always beneficial.
       
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