cyclerage

iTrader: (59)

I just noticed that I have a noticeable amount of blow by coming from my oil cap if I take it off when running? I only have about 50K on the bottom end. Just did heads and now have 11.3 to 1 comp.. I did a compression test and everthing looked good, with in 2-3psi of each other. Could this have something to do with the stock LS1 vent system?
thanks

sleeperstyle

iTrader: (4)

get a catchcan (not sure where to buy one but im sure if you researched it you could come up with one and an install guide). a cylinder leakdown test is not a bad idea either since the compression is good if you are that worried about it.

that way you can really monitor oil blow-by, pulling off your oil cap doesn't really tell you how much you are getting.

other than that i personally would check my oil daily and make sure it doesn't get low- that is pretty much all you can do for now..

crainholio

iTrader: (2)

The easiest way to quantify blow-by is a leakdown test. I did both my LS1 longblocks at 100psi using a Total Seal leakdown gauge, each cyl at TDC. Had to loosen the rockers and give each valve a few taps w/ the rubber mallet to get them seated (engine had been sitting for months).

Both engines, as well as my 4.8L truck, returned numbers in the 95%-98% range which is excellent.

In general, compression tests are only good for diagnosing a completely failed engine.