Adis

Under heavy boost my blown LS3 (stock engine, ECS centri SC package) blows oils out the exhaust. An inspection of the spark plugs looks like they are all pretty good. Compression test shows average 185-193, except for #5 which is 148. ALSO, under high boost, I think the crankcase is not venting properly (I've still got the stock PCV plumbing, with a RX dual valve catch can) and the excess pressure is finding it's way out my rear main seal, oil filter, and pan bolts. I don't know if the oil out the exhaust is caused by overpressure (fixed by venting the block) or if something bad happened in #5. What's my next troubleshooting step? Will a leakdown test help me pinpoint where the problem in #5 is? Or do I even need to bother - just get the head off and see what's broken in there? I think if I route my dirty side PCV from the driver's valve cover instead of the valley port, that might provide the necessary flow to evacuate the block under boost, but I think that I still have something lurking in #5...thanks for any suggestions. - mark

hangtime204

I was thinking a leakdown test as well. First though, using an oil can, apply 2 drops into cyl. 5 and do a compression test. If your numbers rise, you know its the rings.

Yawlak80-86