Uneven rear main seal, help needed.

[Nick88]

Hey guys I'm building a 383 stroker out of an 86 350 1 piece rear main block.
The issue is I got the seal on but even when I spin the crank a bunch to align it, it has an uneven gap around the seal. The driver side is tight and the passenger has a noticeable gap around the outer seal, I assume the inner seal is fine because it was nice and tight. Any ideas? I can align the outer lip by hand to be even but if I spin the crank it goes right back. First picture is tight side second is loose side, thanks.

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[Edelbrock]

I would pop that seal out and try a different brand.

 

[Ricko1966]

Hey guys I'm building a 383 stroker out of an 86 350 1 piece rear main block.
The issue is I got the seal on but even when I spin the crank a bunch to align it, it has an uneven gap around the seal. The driver side is tight and the passenger has a noticeable gap around the outer seal, I assume the inner seal is fine because it was nice and tight. Any ideas? I can align the outer lip by hand to be even but if I spin the crank it goes right back. First picture is tight side second is loose side, thanks.

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Are you centering the rear plate as an assembly then very slowly creeping up on final torque as you are tightening the mounting plate. The friction from tightening the bolts can pull the mounting plate off center. Okay I just reread your post. Bolt a piece of coat hanger to 1 or 2 oil pan bolts. Bend it around to the crank to make a pointer. Bend your pointer as close to the side of the crank flange as possible. I mean thousandth of an Inch from touching. Rotate your crank can you witness the crank getting closer and farther from your pointer? No,that's good. Now measure your gap careful with feeler gauges,don't let the feeler gauge move your pointer. Now rotate the crank to several positions,keep checking that gap. Suspicious of runout on the crank flange. You could probably make better jig with 2 pieces of strap iron, one bolted to the pan mount rail and a second bolted to the end of it. Between pivoting on the pan bolt and using a bolt as a hinge between the 2 pieces of strap you should be apple to create a stable reference point.

 

[Nick88]

Are you centering the rear plate as an assembly then very slowly creeping up on final torque as you are tightening the mounting plate. The friction from tightening the bolts can pull the mounting plate off center. Okay I just reread your post. Bolt a piece of coat hanger to 1 or 2 oil pan bolts. Bend it around to the crank to make a pointer. Bend your pointer as close to the side of the crank flange as possible. I mean thousandth of an Inch from touching. Rotate your crank can you witness the crank getting closer and farther from your pointer? No,that's good. Now measure your gap careful with feeler gauges,don't let the feeler gauge move your pointer. Now rotate the crank to several positions,keep checking that gap. Suspicious of runout on the crank flange. You could probably make better jig with 2 pieces of strap iron, one bolted to the pan mount rail and a second bolted to the end of it. Between pivoting on the pan bolt and using a bolt as a hinge between the 2 pieces of strap you should be apple to create a stable reference point.

I don't really understand what your saying to be honest.

 

[Ricko1966]

Okay in your pic 1 that black bolt head to the right of your crank that is a fixed point,it doesn't move. Now let's say that bolt head was .020 from the side of the crank you could watch that .020 gap while you turned the crank. If that gap grew to .030 and shrank to .010 as you turned the crank it would indicate that the rear flange isn't running true it has 010 runout. What I'm saying is create a fixed point close enough to the crank to watch a gap open and close. Better yet, that you can measure the gap at several different crankshaft positions using feeler gauges, maybe you could replace that black bolt with a longer bolt and a piece of thick sheet metal to create a fixed reference point,a few thousandth s to the right of the crank flange. If the crank flange isn't running true,that is the problem. I just reread your post again. If the tight spot is always In the same spot,it's not crank run out. Have you tried putting the seal and plate in the middle position and just bolting it down,carefully tightening the bolts a little at a time,being very careful not to let the plate move? If that doesn't work remove the seal turn it 180* reinstall, does the tight spot move 180 degrees. If so I'd Suspect the seal it self if the problem stays in the same spot,I'd carefully measure and examine the mount plate for a problem. Pull the seal measure from the mount plate seal area where it's tight,to the crank. Do the same thing on the other side. Are the diamensions the same?

 

[Nick88]

Okay in your pic 1 that black bolt head to the right of your crank that is a fixed point,it doesn't move. Now let's say that bolt head was .020 from the side of the crank you could watch that .020 gap while you turned the crank. If that gap grew to .030 and shrank to .010 as you turned the crank it would indicate that the rear flange isn't running true it has 010 runout. What I'm saying is create a fixed point close enough to the crank to watch a gap open and close. Better yet, that you can measure the gap at several different crankshaft positions using feeler gauges, maybe you could replace that black bolt with a longer bolt and a piece of thick sheet metal to create a fixed reference point,a few thousandth s to the right of the crank flange. If the crank flange isn't running true,that is the problem. I just reread your post again. If the tight spot is always In the same spot,it's not crank run out. Have you tried putting the seal and plate in the middle position and just bolting it down,carefully tightening the bolts a little at a time,being very careful not to let the plate move? If that doesn't work remove the seal turn it 180* reinstall, does the tight spot move 180 degrees. If so I'd Suspect the seal it self if the problem stays in the same spot,I'd carefully measure and examine the mount plate for a problem. Pull the seal measure from the mount plate seal area where it's tight,to the crank. Do the same thing on the other side. Are the diamensionsbtge same?

Ok I see what your saying now. I used a different seal before that I screwed up so I put in this one instead but the other one had the same weird gap at thst one point, I don't know why, everything is brand new eagle parts for the rotating assembly. I'll have to measure it out figure out what is going on.

 

[fast 99]

That condition is real odd. Could the seal housing be bent? It's an aluminum piece, careless removal or dropping the engine could easily bend it. Provided the crank doesn't have runout I would find another housing.

 

[hey mister]

Curious....
Do you have an indicator and a magnetic base.?
If so, check the runout on the crank.
New parts can be damaged in shipping.

 

[Ricko1966]

Make a mark on the housing where the tight spot is,make another mark where the loose spot is. Pull the seal,measure the gap between the housing and the crank flange at the tight spot,and again at the loose spot. I think the housing is damaged. Even if you don't have anything to precisely measure with here's a little trick take a piece of thin cardboard cut a strip that just fits between the flange and the housing at the tight spot. Now slip it in on the loose side can you see a gap? If you see a gap,pull the plate,cut another cardboard strip that will fit from the tight spot straight across to the other side. Rotate that strip 90 degrees if there's a gap the bore in the housing is oblong.