Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - Blown bbc too much crankace pressure
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Old 08-12-2012, 02:31 AM
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Agree. The ring seal is not what you think it is. 95 PSI on a cranking test is way too low.
You want 150psi. Was the throttle open during the compression test? ya it matters.
Connect shop air the the cylinder and listen for air leak ( carbs, exhaust, valve covers)
bent,cooked valves, wrong size, failed, butted or upside down rings, rings bent on install Broken ring land(s),,, both) Wrong honing stones for chrome rings.

.024" ring end gap is too small for a blown BBC.

You probabily butted the rings and scuffed the rings and cylinder walls.
If the motor ever detonated or pri-ignited Lean carbs, crap gas or got hot even .080" ring end gap may not be enough.
If you are lucky and have not distorted the piston ring lands or lifted a ring land you may be able to just rehone re ring it.
Check the bearings and piston pins.

The .650" BBC roller is not big duration.

Check the valves for bent stems and VTP clearance.
possible leaking head gaskets.

Are these pistons stock 454 HO crate motor pistons?

Last edited by F-BIRD'88; 08-12-2012 at 02:56 AM.
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