Revision troule after exhaust change?
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Revision troule after exhaust change?

  1. #1
    Senior Member crf311's Avatar
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    Default Revision troule after exhaust change?

    Looking to get some input as to "is my cam too big for my exhaust". Changed exhaust now I have revision issues!

    engine is a BBC gen V 454, 9.5CR, steel heads, cam spec: solid lifter, 249/254 @.050, .615I/.626E lift, 110 lobe sep, 106CL with 4deg adv.

    My motor was built for OT headers and I never had a issue, switched to some lighting headers with no issue, only they didn't last with the salt water down here, no knock on them I just purchased wrong ones for freshwater.

    Picked up a set of KE cast alum headers with bravo tips, made some S bends to go thru the transom, and ended up with revision problems.

    I think I'm going to go with a retrohydr roller cam setup with the following:
    230/[email protected], lift .323/.323, 112 lobe sep, 110 CL.

    What you think? Thanks
    Last edited by crf311; 06-24-2015 at 09:29 AM.
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  3. #2
    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by crf311 View Post
    Looking to get some input as to "is my cam too big for my exhaust". Changed exhaust now I have revision issues!

    engine is a BBC gen V 454, 9.5CR, steel heads, cam spec: solid lifter, 249/254 @.050, .615I/.626E lift, 110 lobe sep, 106CL with 4deg adv.

    My motor was built for OT headers and I never had a issue, switched to some lighting headers with no issue, only they didn't last with the salt water down here, no knock on them I just purchased wrong ones for freshwater.

    Picked up a set of KE cast alum headers with bravo tips, made some S bends to go thru the transom, and ended up with revision problems.

    I think I'm going to go with a retrohydr roller cam setup with the following:
    230/[email protected], lift .323/.323, 112 lobe sep, 110 CL.

    What you think? Thanks

    Likely a combo of the duration @ 50 and lobe center , where does the exiting water actually enter the exaust system relative to the end of the rizer (vs the vertical center line of the manifold ?
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    Senior Member tigertooth's Avatar
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    So. Is the cam installed at 106 or 102. 4degrees ahead is 106. If its ahead of that its openi g the exhaust valve too soon. I would install it at 108. Just my .02
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    Senior Member crf311's Avatar
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    Quote Originally Posted by jetboatperformance View Post

    Likely a combo of the duration @ 50 and lobe center , where does the exiting water actually enter the exaust system relative to the end of the rizer (vs the vertical center line of the manifold ?
    Tom
    the water enters about 2-3 inches behind the end of the riser. It looks like the water entry point is only a few inches below the lowest bend in the mainifolds.
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  7. #5
    Senior Member crf311's Avatar
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    Quote Originally Posted by tigertooth View Post
    So. Is the cam installed at 106 or 102. 4degrees ahead is 106. If its ahead of that its openi g the exhaust valve too soon. I would install it at 108. Just my .02

    Tiger, That's the spec off the cam card. It has 4 deg. built into it. I's been so long I don't remember how many deg I installed it with. Built it the month before Katrina hit. Thanks for the help.
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    Senior Member DuaneHTP's Avatar
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    Make sure the gaskets between the risers and the manifolds are good. Leak there will cause that problem.
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