302s on 72 340

rigger3006 said

this 72 340 doesnt run very nice, its been parked since 92, anything past about 4000 rpm it just starts breaking up,, imo the heads are shot, cam was looking a little suspect also, it had been reringed in 85, still has crosshatches in bores. plus i dont mind experimenting, especially against the given norm, otherwise you'll never know for sure

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Only two ways to diagnose ,two ways to find out piston/deck height : Latter first:Do a leakdown rent/ beg borrow a b oroscope ,or yank the heads. Sounds like the heads you have ,are better than what you have on it. Run a thicker head gasket, if needed. Grinding those chambers down: Get some dykem, scribe it against the head gaskets you decide to use. Cam timing comes into effect,about bleeding off compression. Some of the slower ramp camshafts ,( budget grinds,most likely..)work really well here.