Whenever I drive my recently rebuilt 355 with an lt4 cam and hv oil pump hard, it seems to leak oil out of the rear of a 1pc oil pan gasket. Is this normal? There is a breather on one of the valve covers while the other has a PCV valve hooked up to the throttle body. Would this be a crankcase pressure problem?

 

Possibly because your PCV is hooked up wrong and your have no vac on it to make it work.

Where exactly ?
Is the gasket fitted correctly ?
Have you confirmed the oil is not leaking down from somewhere up top ; a very common problem ?

Why have you got a HV pump?
Are know to cause problems by pumping way too much oil around ; more than needed

 

I checked the rear main and there is no leak, oil is seeping out of the 1pc pan gasket on the rear. I figured since I was shooting for over 400hp, a high volume oil pump would be a good investment. When is a hv oil pump needed on a 350?

 

Do a GOOGLE search about HV SBC pumps; pros and cons
Like
http://www.hotrodders.com/forum/high...tml#post834173
http://www.hotrodders.com/forum/high...utor-5521.html
http://speedtalk.com/forum/viewtopic.php?t=763

The argument goes, on a low level ( street driven, not race ) engine , a HV pump will use up more Hp to drive the larger pump
will pump too much oil up top where it is not needed and has the potential to drain a stock oil pan dry under the right conditions
because the oil can't return to the pan fast enough.
Also plenty of opposite ideas.

 

O jeeze, I will have to take the risk, it would only be pumping 20% more oil throughout the block. The motor revs up to 6000 rpm, but only for drag racing. I guess if I ever do any track racing, I'll have to switch over to a larger capacity oil pan.

 

Ok, I'm100% sure the HV oil pump is causing the leak, so I'm pulling the motor out and replacing the oil pump with a standard volume unit.

 

What did you find that makes you 100% sure that this is the problem? Did you use RTV in the corners of the pan gasket? Was the pan tightened down evenly so the pan rails wouldn't warp? Is it a new or used pan?

HV pumps don't cause leaks (unless installed wrong, which won't be fixed by installing a standard pump the same way). It's possible they drain the oil from the pan too fast but if anything that would keep a leak from occuring.

 

It's a 1pc oil pan gasket, rtv was used on the corners, oil pan bolts tightened to spec, rear main seal is correctly installed. I took the motor up to 6000rpm and there was a stream of oil burned on the stainless steel header pipes. The oil pressure was above 60psi, or above the whole reading area of the gauge. There was oil dripping from the dipstick tube mount area, oil leaking from the oil filter seal, there was a drip from the oil pressure sending unit, and there was oil leaking from the rear main and rear oil pan gasket area. When I saw oil was leaking from the oil filter seal (It was on tight) I was convinced the high volume pump has to go.