A couple weeks ago I completed installing a brand new motor in my 87 IROC. These are the main components-zz4 short block, trick flow 64cc heads, crane cam I 214deg, E222deg, I488lift, E509lift, and an SLP T-RAM intake. It developed a bottom end rattle after about 60 miles. I removed the engine and found the rear thrust bearing hammered. While the motor was in the car I checked the cranking compression and was shocked to see 200psi from every cylinder. The zz4 long block uses 58cc heads to bring its CR to 10 to 1, so theoretically my 64cc heads should have kept the CR at an acceptable level. Am I correct to assume that the cam is the culprit for extreme cylinder pressure? Any advice will be gratefully appreciated.

 

did u break the motor in correctly?

 

Sounds like your crankshaft wasn't machined properly. The most common cause for the rear thrust bearing getting tore up like that is excessive crankshaft endplay. If your engine is still under any kind of warranty, I'd definitely be contacting the people who sold it to you. If you had a machine shop work on your crank, I'd be throwing a crankshaft at the guy who machines them!



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89RS w/350 TPI; 69RS/SS w/450 HP 350/Muncie 4-Speed "Too weird to live, too rare to die."