Hey I'm taking this all in......looking at everything thats posted I wont rule anyones ideas out. One thing to remember is that the thing ran for 30-40 min without leaking a drop then on seatrial it puked most of the capacity 7 qts in the bilge this is not a drip or pan leak at an idle it will puke a qt in under a min.......i

Wow!

I have a very similar problem to a freshly (1 month ago) built 383 small block (orig 260hp mercruiser).

Last Sunday, while cruising at 3000 rpm, engine started running rough and well zero psi on the oil gauge. Shut the engine down and got a tow ($225). At least 4 quarts at the bottom of the bilge. Saw some oil once before in the bilge, but did not occur again until last Sunday. This thread has been some good insight. Thanks everyone!

My plan: TRY TO FIND THE LEAK!

1) put pressure gauge on end of dipstick tube to see if excessive crankcase pressure. Development engineer at my office said "rule of thumb" for crankshaft oilseals is a max of 2 PSI (4 inHg). Over that and leak prone. That should indicate blow-by amount and PCV breather effectiveness.

2) Wash engine with engine cleaner and put fluorescent die (suppose to get for $3 from NAPA autoparts) in oil and search for leak with blacklight.

Problem is, mighgt have to go out and try to recreate failure scenario of cruising at 3000 rpm and try to not run completely out of oil again.

My episode of "this old boat!"

if its too big you'd think it would have leaked the whole time but if the seal is too small dia. than it may have been tight and torn or distorted atfer some running time. I'd knock off the balancer and get a better look.

Balancer is off and the seal is out...but you know the only way to get them out is to damage them....so the findings are questionable.....

well let us know what you come up with, I hate to se this happen to someone mid season cause it always happens to me and it sucks.

I get out at 2:00 and I'll be hangin upside down soon after I'll let you all know what happens. Thanks to all!!!!!!!

Most of the time pvc breathers ar'nt enough, especially on a super charged engine or running high rpms. You need the big valve cover breathers with at least a 1" hole through the breather, especially on a small block

Are you sure that the oil is not running out the dip stick. It could be that your Valve Cover Breathers are okay at low RPM but allow the crankcase to build pressure after that. Take the breathers off just to make sure. Run it back up to the same RPM.

Good luck,

Bob

Bob nothing out the stick.....but the breathers are coiming off tonight new seal check the accessery holes and we can try it again...wish me luck I'm out of here!!!

Dyno,
If you can wait a few, I have one of our guys going to fit a gen v pan on a gen 4 oil pan fixture with gasket and torque it down to see what happens.

Their are 3 different covers, but their are only 2 different seal types. When the Gen 6 was derived, GM kept the bottom of the cover the same as the Gen V so the existing oil pan design could be used, but with minor mods a Gen V covers will go on a gen 6.



Chris