327 Revisit

[TBARA Wildchild]

Help! Just had my 64-66 corvette motor rebuilt, it also had the canister under the intake. My problem is oil leaks!! We have tried every thing but for some reason I have too much crank case pressure. Motor has about 3500 miles since being rebuild. Motor has new- cam, lifters,cam bearings,10/10 crank, 3 new rods,rings,oil pump,pushrods,rod bearings,main bearings,pistons,freeze plugs, timing gears and chain, new timing cover, front seal, rear seal, heads have been redone and all numbers match so it is a true corvette 327. Now when I got the motor it leaked at front seal and at rear seal. We found out that the canister was plugged. We plugged the outlet to the canister and put a pvc in one valve cover to carb and a breather in other valve cover that goes to the air cleaner. leaked at the front seal. So now we are moving the pvc to where the canister came out the block and running it to carb and breather on both valve covers. Won't know
till tomorrow if that will work so i thought i would ask you guys what you think it could be??

Doug

 

[Gastrick]

Doug,

When you say it's leaking from the front seal, do you mean from the crank seal in the timing chain cover or the front part of the pan gasket that goes between the bottom of the timing chain cover and the oil pan.

Check the oil and see if it smells like gasoline. It's possible that the rings aren't seated and cylinder pressure is pushing pass the rings into the crankcase.

It seems like that with a properly functioning pcv that it wouldn't be possible to build enough pressure to push oil out of the seals

I'm not trying to be a jerk but have you double checked the obvious like too much oil in the crankcase or bad gaskets and/or seals and if the crank snout has a groove worn it where it contacts the front seal?

 

[bob w]

Along with what Gastrick offered, if you have a chrome oil pan leaks are common. First, many are not formed real accurately and the smooth chrome surface will not seal well. It is a good idea to sand the sealing surfaces to roughen them up a bit. Also, there is a thick and a thin front pan seal. The correct one for the pan you have needs to be used.
If the balancer has a groove in it as Gastrick mentioned, there is a repair sleeve that can be used to save it.

 

[TBARA Wildchild]

Yea, Thanks guys for the replys! It had a chrome oil pan now changed to stock steel pan, that was the cause for the rear leak. Gastrick, it was leaking from the front timing seal thought it was the chrome cover,now has a brand new steel timing cover and we siliconed the seal to the timing cover ,leak then went to fuel pump cover, siliconed that ,now is leaking between front of oil pan and timing cover. It's a leak that is finding the weakest link and then leaking. Oh, also put on new harmonic balancer,Had a 350 went to 327 balancer. What really is weird every time we pull the pan we put on all new gaskets!! That's when we asked a guy that does nothing but build race motors what it could be and he's the one that came up with this last placement of the pvc. Also said that early vette motors had a windage tray and that might help, which we well add if this didn't work!! It also had the oil and filter changed at 500 miles,1000 miles, And at 3000miles then this oil problem at the timing cover seal started. Been chasing it ever since.

Doug

 

[TBARA Wildchild]

Well got the motor back and NO LEAKS!(knock on wood!!) so we didn't have to go with a windage tray. Any ideas why this worked?? I did find out that the heads are what they call power pack heads that GM put on the vette 327 before the camel humps. But it was touch and go,the motor and the truck it's in almost became a boat anchor!!!!

Doug

 

[Gastrick]

I think it was just a batch of bad luck with the gaskets, especially if you switched to synthetic oil at the oil change. Synthetic oil seems to exploit weak links in the sealing matrix. Well I'm glad it doesn't leak now. I was going to add one more suggestion that I forgot about. I usually put a dab of silicone in the key slot in the balancer during assembly. Sometimes oil finds it's way through there.

Now you'll have to by a new anchor for your boat