Killer Oil Leak

Mattcleaver

Member
Apr 20, 2020
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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
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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

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Apr 20, 2020
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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
899
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
899
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

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Apr 20, 2020
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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
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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

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Apr 20, 2020
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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
 

prairiehotrodder

Pro Stocker
Dec 17, 2005
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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 ?
 

Mattcleaver

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Apr 20, 2020
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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.
That might be our next move if we can’t figure it out. We always put a liberal amount of oil on the balancer before pressing it on. We never actually remover the crank gear from before we rebuilt the motor. All the machine work was done with the gear still in place. The motor didn’t leak before it was rebuilt so I’m assuming the crank gear is not the issue. If the machine shop that did the work for us opens back up with the coronavirus stuff, we may trailer the car there and have a professional look at it. We have a decent amount of knowledge on the topic but have exhausted all our options so maybe a professional can help.
 

Mattcleaver

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Apr 20, 2020
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Just took the balancer back off. You can see the two lines where the front and back of the seal were riding so the balancer was fully seated. I’m at a complete loss.
1F84F8FC-8E41-440D-A8A8-FF5CB11D3100.jpeg
 

prairiehotrodder

Pro Stocker
Dec 17, 2005
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maybe you are running it way to full of oil so that oil is always sloshing in the timing cover and up against the seal ? I don't know what else to tell you.
 

Mattcleaver

Member
Apr 20, 2020
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maybe you are running it way to full of oil so that oil is always sloshing in the timing cover and up against the seal ? I don't know what else to tell you.
I’m not sure if it makes a difference but we put a dial indicator on the snout of the crank and turned the motor over. Measured about .004 run out. The balancer and pulley seemed to spin straight though. Next thing is figuring out how to measure the clearance to the seal all the way around.
 

Killerdave8813

Dragway Regular
Jan 16, 2008
899
2
18
Cincinnati,Ohio
Any luck yet? .004 isn't much movement at all, any good lip seal would take that in stride as they're designed to deal with slight misalignment issues, what brand seal have you been using? I generally use Felpro exclusively, I was just looking at the pic of your balancer hub, looks kind of odd, that your sleeved one? You said you have purchased a new one that still leaks? You are positive it's leaking between the seal lip and balancer hub? I'd be pulling the seal out of the timing cover and very carefully measuring between the crank snout and the wall the OD of the hole in the timing cover seal outer edge comes in contact with in several different areas around the seal area of the timing cover to make sure the crank snout is actually in the center of the hole, you said the block was out of the machine shop stock as your original was damaged beyond repair? That means you really don't know exactly what's been done to this block over the years? As mentioned earlier If it's been line bored more than one time or even excessively one time that will put the crank center line deeper into the block, that is closer to the camshaft center line and that could cause your constant excessive leak as it would be heavily against the upper lip of the seal and very little pressure against the lower lip, I'm not a pro engine man by any means but I've built my share of small blocks over the years and have seen that issue a time or two so that's where I'd look next as you've exhausted about every other avenue possible that I can see, Good Luck!!
 

Mattcleaver

Member
Apr 20, 2020
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Any luck yet? .004 isn't much movement at all, any good lip seal would take that in stride as they're designed to deal with slight misalignment issues, what brand seal have you been using? I generally use Felpro exclusively, I was just looking at the pic of your balancer hub, looks kind of odd, that your sleeved one? You said you have purchased a new one that still leaks? You are positive it's leaking between the seal lip and balancer hub? I'd be pulling the seal out of the timing cover and very carefully measuring between the crank snout and the wall the OD of the hole in the timing cover seal outer edge comes in contact with in several different areas around the seal area of the timing cover to make sure the crank snout is actually in the center of the hole, you said the block was out of the machine shop stock as your original was damaged beyond repair? That means you really don't know exactly what's been done to this block over the years? As mentioned earlier If it's been line bored more than one time or even excessively one time that will put the crank center line deeper into the block, that is closer to the camshaft center line and that could cause your constant excessive leak as it would be heavily against the upper lip of the seal and very little pressure against the lower lip, I'm not a pro engine man by any means but I've built my share of small blocks over the years and have seen that issue a time or two so that's where I'd look next as you've exhausted about every other avenue possible that I can see, Good Luck!!
We managed to figure it out! We drilled out the alignment pin holes on the timing cover, installed a new seal, installed the cover loosely, installed the balancer, tightened the timing cover, removed the balancer, torqued the bolts, and put it all back together. Must have been misaligned enough. It runs now however and we just did its first real burnout now that we have line locks installed too.
 

Killerdave8813

Dragway Regular
Jan 16, 2008
899
2
18
Cincinnati,Ohio
Good!! Glad you got it whipped! That's the only thing I could think of that could cause a problem like that!

Hey T5, How'er things? Yea I meant to mention a "loose" timing chain would be a good clue as to the possibility of excessive line boring but it got away from me, old brain gets kinda fuzzy sometimes!