I recently purchased a NEW GM 350 short block for assembly with custom heads, cam, etc. The assembly has dropped oil near back of engine from the very beginning and the clutch feels a tad softer than before. I have two theories on this: 1. mechanic pounded on the balancer, causing damage to the seal; or 2. high volume oil pump is producing too much pressure (50-60 lbs. cold). Crankcase is vented with one pleated type vent in a valvecover, plus PCV to carb.

Any advice out there about my diagnosis or a cure? (I think I know how to replace the seal... ugh.)
Billydonn  

Chevy engines with two piece rear seals like
old Harley's mark their spot.

I rather doubt the high volume oil pump contributes more to the leakage than would a stock pump, and crankcase pressure probably isn't a contributor either.

Way back when I bought my 78 Scottsdale from day one it dripped a quart between changes. I complained and the dealer resealed the crank then it dripped 3 quarts between changes. Then they refused to "fix" it again. So I wheeled upder it one Saturday, dropped the pan and rear main and put a new seal and lots of silicon where the seal comes together. It went back to dripping a quart between changes and did that for the rest of that engine's life.

New clutch could be softer than the old, clutches have different spring forces, so unless you know what you have it's not possible to tell whether it's correct. There's an auful lot of Chinese stuff out there made for Chevys that isn't up to spec. Guy a the parts store tried to sell me a Chinese made brake rotor last year, the look on his face when I told him I can't run Chinese parts on my Chevy was priceless.

A common trick for rope and rubber seals alike is install them skewed a bit so their intersection isn't in the same place as the mating line between the bearing cap and the block. In the case of the rubber seal this will require slicing it's ears off, sounds a bit like trophy hunting in Nam. If you do this you need to seal the ends of the seals. I prefer to use a little non hardening Permatex for this as it doesn't make a dimensional comittment by curing hard and any excess that get into the crank to seal interface will be wiped away rather than curing hard and preventing the seal from conforming to the shaft, thus leaking.

Bogie  

Also, check to make sure the oil isn't coming form the top-back part of the engine. A misaligned rear intake manifold gasket, or a leaking oil sending unit would leak oil and it would drip down the bellhousing and look like a rear main is leaking.  

Oldbogie and Phill:
Thanks for your replies. I'm going to drop the pan in spring and try installing a new oil pan gasket (one piece type) and see what happens. The leak isn't big, so it may not be worth doing much more than that. The clutch was not changed in the engine swap, by the way.

Again... appreciate your thoughts.
Billydonn  

Thanks Phill,
Will look over back of engine carefully to see if you were on to something. Could it also just be leaky oil pan gasket? That would drop oil without wetting the clutch wouldn't it?
Billydonn  

Yes it would. If you used the older style multi-piece pan gasket, these are notorious for leaky if not installed exactly right. A good Fel Pro one-piece pan gasket is defnitely worth the money, I think they only cost about $30. That's what I remember when I put on on my truck.