Pushrod question
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Pushrod question

  1. #1
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    Default Pushrod question

    Have had numerous issues with valve train on older 396. Originally had low oil flow to top end, had camshaft grooved at rear bearing, massive oil flow now. Put motor back together ran on hose for 20 minutes. Took boat to the lake ran for approx. 2 minutes and started to run rough, found 1 broken intake pushrod and all other intake pushrods bent, exhaust are all fine.

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  3. #2
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    Are you sure of your valve to piston clearance? The intakes are the ones that run close.

    Or could be coil bind.

    Tim
    Last edited by River Rat 005; 06-03-2010 at 10:56 AM.

  4. #3
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    Quote Originally Posted by River Rat 005 View Post
    Are you sure of your valve to piston clearance? The intakes are the ones that run close.

    Or could be coil bind.

    Tim
    Just getting ready to pull heads, thanks

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  6. #4
    gn7
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    Intakes valves chase the piston down the hole. Pistons chase exhaust valves back to their seats. Much easier to smack a exhaust. Float em, and you find out. Nobody ever hit a floating intake. You are in coil bind. Cam most likely has slightly more lift on the intake side. If you are in coil bind(stock springs?) you need to replace them all. Assume the cam isn't stock, due to the fact that it wasn't grooved to begin with. Stock BBC springs, specially early ones, don't have much in the way of valve spring when it comes to lift.



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    Last edited by gn7; 06-03-2010 at 02:24 PM.

  7. #5
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    Default Pushrod issue

    Did not take long to figure out what happened. I had purchased a new timing chain and gears that had multiple marks on it, i had the valve timing off. Needless to say the intake vales all paid a visit to the top of the pistons. Pistons are all ok, took the heads to the machine shop for new intake valves.....Hopefully this third time will be a charm....I am wearing my motor mount bolts out.

  8. #6
    Senior Member jet460's Avatar
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    Had a set of Keith Black pistons installed backward in my BBC some years ago, and had the same thing happen. KB pistons are notched in the back, instead of front, so the valve reliefs were backwards.

    A mistake you make ONCE.

  9. #7
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    I just had a customer's engine this week that was built by his local machine shop that had the pistons put in backwards. Waiting for him to get them turned around and bring it back so we can proceed. Fairly common mistake.
    Duane HTP

  10. #8
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    Thats why I asked about the valve to piston. The more the cam advance the less clearance there is.

    Tim

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