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Old 03-06-2013, 08:53 AM
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Cut your losses

Originally Posted by 1fast62 View Post
hey guys,
i checked my piston to valve clearence on my bbc.. it has kb pistons with a .250 dome height.
i have a set of 781 heads and i checked the clearence and it was 58 thous. i was reading you need a min of 80 thous. is there anything i can do besides fly cutting the pistons. and im running a 40 thous gasket already.
thanks for the help as usual.
Brandon, I know this is not what you want to hear, but its the best common sense advise I can give you as a young hotrodder.

While I admire your tenacity at trying to do this yourself, maybe its time to reconsider everything about the build,cut your losses and pay a pro engine builder to assemble it for you. Usually assembly costs are not that high if all the parts are there. I mean that with all the expensive parts you've destroyed in multiple attempts to DIY, get a pro to put it together and if you ask him, he may let you come hang around while he's doing it and teach you a thing or two.

Also I'd like to point out that if you're still trying to use that big butt bertha mutha trucking thumper bumper cam(or whatever they call them) (249/255@.050-.663/683) ? Its wayyy too much for what you're trying to accomplish especially with the 781 heads.

If you just have to have a big dog cam, consider one a bit smaller than the Lunati, perhaps a Comp 292, but get it with a 112 LSA. This way you're not likely to have PTV clearance issues. With the wider lobe separation the piston is farther down in the bore when the valves are at full lift eliminating most PTV clearance issues. The little bit of low end torque you loose with the 112 LSA versus a 110 or 108 will help it hook out of the hole and you'll gain it back in the midrange and top end.

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