Killer Oil Leak

Mattcleaver

Daily Driver
Apr 20, 2020
13
0
1
23
Hey guys, this is my first time on this forum. My friend and I (both 18) rebuilt a 383 stoker sbc for his 1980 malibu coupe last year. The engine runs like a top besides one killer issue. We have a a constant oil leak from the front main seal that we absolutely cannot figure out. We’ve change the seal 4 times, sleeved the balancer, bought a new balancer, changed out the timing chain cover and pulled the motor multiple times. We can’t keep chasing this leak around. The engine runs like a top and sounds great but just leaks oil constantly. It’s driving us nuts and between being at college and all, has wasted about a year of our life. Please help with any possible insight! I’ll post pics if you guys think it will help. Thanks in advance!
 

prairiehotrodder

Pro Stocker
Dec 17, 2005
1,576
4
38
46
Melfort Saskatchewan Canada
you have to have the right pan gasket depending on if you have the thin or the thick front seal. Also what timing cover gasket are you using ? The felpro performance gasket is hard and thin and doesn't crush enough for use with a stock tin cover and will leak between the bolts and near the dowels.
Also has your block been aligned excessively so that the crank is no longer in the middle of the timing cover seal ?
 

Mattcleaver

Daily Driver
Thread starter
Apr 20, 2020
13
0
1
23
you have to have the right pan gasket depending on if you have the thin or the thick front seal. Also what timing cover gasket are you using ? The felpro performance gasket is hard and thin and doesn't crush enough for use with a stock tin cover and will leak between the bolts and near the dowels.
Also has your block been aligned excessively so that the crank is no longer in the middle of the timing cover seal ?
The timing cover and gasket were using is mr gasket brand, our last resort when trying to eliminate this leak. The pan gasket is a felpro one piece rubber one, seemed like it fit tight against the cover. As far as the crank being in the middle of the seal, that I don’t know. The block came from the stock at the machine shop because the other one had 2 cracked cylinder walls.
 

Killerdave8813

Dragway Regular
Jan 16, 2008
904
2
18
Cincinnati,Ohio
Chrome timing cover? Stock or a good aluminum ones are best and as prairiehotrodder says I've seen line bored blocks where the center line of the crank has been changed enough that you have to wallow the line up pin holes in the timing cover to get the seal centered on the harmonic balancer, it's a pain to do but it's best to have the engine out, pan off, put the timing cover without a seal in the engine block and carefully measure the distances from the crank to the edges of the seal land and make sure they're all the same, if not modify the pin holes as needed to get the correct measurements, once completed install your seal, put the timing cover on loosely with your favorite sealant on the gasket and then install the balancer before you snug up your bolts, that should center your seal on the balancer, then install your pan and so on, personally I've not had very good luck with the one piece pan gaskets and rely on the old four piece jobs, some do have good luck with them though, oil leaks can be a pain, that's for sure! Hope this helps!! KillerDave
 

Killerdave8813

Dragway Regular
Jan 16, 2008
904
2
18
Cincinnati,Ohio
I had another thought after talking to a cat here at work during lunch, he said he's seen aftermarket timing covers made to where the hole for the seal wasn't perfectly centered in the cover, and since he mentioned it I have seen that as well, aftermarket especially stamped chrome steel covers can always be suspect, even with good names like Mr. Gasket, Good Luck!, KillerDave
 

Mattcleaver

Daily Driver
Thread starter
Apr 20, 2020
13
0
1
23
I had another thought after talking to a cat here at work during lunch, he said he's seen aftermarket timing covers made to where the hole for the seal wasn't perfectly centered in the cover, and since he mentioned it I have seen that as well, aftermarket especially stamped chrome steel covers can always be suspect, even with good names like Mr. Gasket, Good Luck!, KillerDave
The leak persisted with a high quality cast aluminum timing cover from edelbrock and a factory GM cover. Otherwise I’d say that’s definitely something to check. Right now we think it might be that the balancer is not seating fully on the crank. From what we can tell it’s stopping when it hits the key for the timing gear. We’re still looking into it though. Thanks for the responses guy. Keep em coming!
 

prairiehotrodder

Pro Stocker
Dec 17, 2005
1,576
4
38
46
Melfort Saskatchewan Canada
I like the one piece felpro pan gasket and the stock replacement timing cover gasket. I do not like the high performance timing cover gasket. I have seen guys put a gob of RTV on the key way to keep oil from migrating through the key but it has never been an issue for me. If your balancer is not going on all the way that definitely needs to be figured out.
 

Mattcleaver

Daily Driver
Thread starter
Apr 20, 2020
13
0
1
23
I like the one piece felpro pan gasket and the stock replacement timing cover gasket. I do not like the high performance timing cover gasket. I have seen guys put a gob of RTV on the key way to keep oil from migrating through the key but it has never been an issue for me. If your balancer is not going on all the way that definitely needs to be figured out.
Here are some pictures Incase they help. It’s not leaking between the pan and cover, just the front main seal. Just ran it again with a different balancer that I cranked all the way down until it hit a hard stop and it still leaked.
67A15636-76CB-478D-9EE4-73FDFDE02CCD.jpeg
47AA43C7-675D-4070-8641-DE665CC82007.jpeg
 

Mattcleaver

Daily Driver
Thread starter
Apr 20, 2020
13
0
1
23
Here’s another. Sorry for the bad picture quality we’re working out of a poorly lit shed.
A1B6F16E-231A-40DD-98ED-F9600F767A03.jpeg
 

prairiehotrodder

Pro Stocker
Dec 17, 2005
1,576
4
38
46
Melfort Saskatchewan Canada
if you take the cover back off, lay a straight edge across the cam and crank gears to see if they are lined up. Maybe the crank gear is on backwards ? If it sticks out farther then the balancer will not be on all the way. Also be sure to not assemble the seal dry. I always put white grease on it before i press on the balancer.

EDIT: i guess you wouldn't have a timing mark if the gear was on backwards but maybe something is holding it from going on all the way ?
 

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