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BBC rear main leak

General engine tech -- Drag Racing to Circle Track

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AA Performance
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BBC rear main leak

Post by AA Performance »

Just pulled engine after refresh and this is were the leak came from. Definetley looks like a seal fault. Just wondering if Felpro would be liable for the cost involved in pulling the engine and replacing the seal. The seal has the edge that rides and seals on the crank surface gone. It is only about 2mm of the corner gone. Did a smoke test before pulling the engine and that confirmed it. Definetley getting sick of all the poor quality control of parts now a days.
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Re: BBC rear main leak

Post by AA Performance »

This is the other side for comparison
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Re: BBC rear main leak

Post by Dave Koehler »

All that special silicone where it is and where it is not doesn't bode well for your case
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Re: BBC rear main leak

Post by BillK »

Dave Koehler wrote: Sat Nov 12, 2022 9:47 pm All that special silicone where it is and where it is not doesn't bode well for your case
Agreed :( Should not be any in the area. And I am not sure exactly what part of the seal is supposed to be "missing" ??
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Re: BBC rear main leak

Post by Tom68 »

BillK wrote: Sat Nov 12, 2022 9:57 pm
Dave Koehler wrote: Sat Nov 12, 2022 9:47 pm All that special silicone where it is and where it is not doesn't bode well for your case
Agreed :( Should not be any in the area. And I am not sure exactly what part of the seal is supposed to be "missing" ??
Corner of the sealing lip is gone, he'd have to prove it was lubed though.
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Re: BBC rear main leak

Post by AA Performance »

BillK wrote: Sat Nov 12, 2022 9:57 pm
Agreed :( Should not be any in the area. And I am not sure exactly what part of the seal is supposed to be "missing" ??
You cant see the difference between the 2 pics?? Are you familiar were rear main seals actually seal on the crank? The sealing edge is not there on the first pic. It is only about 2 mm of the corner that isn't there and that is were it was leaking from. Sealer is there for the main cap to seal on the block. Obviousley was a small dab which spreads out but have had issues in the past so I wont let it go dry anymore. It even looks like the dust seal isn't even riding on the crank as well. Cant see this seal as not being a defective one. Many yerars ago had no isuues with oil leaks but over the last 10 years things have began to get worse so I started only using the "better" viton seals but even they have issues as can be easily seen. Is there any other better brands available? Heard Mr Gasket are suppose to be hit and miss as well. Cometic??
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Re: BBC rear main leak

Post by allencr267 »

Ya gotta look at this stuff before it goes in, sad but true. Touching it, twisting it, fondle & feeling it to make sure it's all there and ain't got any bad spots.
Also, silicone/RTV IMO is just for filling gaps, like .002-3" & over, not for flat machined surfaces or the 2-piece seal's ends, though it does inadvertently seal them, but that's only from the stuff that oozes & hangs on at the parting line. JMO.
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Re: BBC rear main leak

Post by Dave Koehler »

AA,
I would like to see you put a new seal in there without the silicone just to verify things.

FWIW I use the Ford gambit of offsetting the seals and a very thin film of sealer at the rear of the cap face.
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Re: BBC rear main leak

Post by prairiehotrodder »

i often use permatex flange sealant for the length of the cap at the very back of the block. Not on the rear main seal itself. And don't assemble it dry or let it sit for a long time so that it goes dry before you run it. I wouldn't expect any help from felpro. I'm not saying you installed it wrong, but they probably see stuff don't wrong every day.
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Re: BBC rear main leak

Post by 1980RS »

I use the Felpro blue rear main seals and off set the two halves slightly in the block and never had a main seal leak yet.
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Re: BBC rear main leak

Post by rebelrouser »

Just from my experience you will be hard pressed to get a seal company to pay a big repair bill for labor. And as mentioned if you show them that picture with gobs of silicone under the seal I am sure they will not pay the claim. I have used a little silicone under the seal from time to time and the weight of the crankshaft should have pushed it down. I see a void under the seal. Which would maybe make it leak. Was the engine line bored? The only issues I have ever had with a chevy rear main leak is on engines that have been line bored. Felpro makes a rear seal just for engines that have been line bored.

As far as rear seals go I just pulled one out of an engine gasket kit for a SBC that I throwed away because of the way it fit. The quality of parts is getting to be a real problem, you have to double check everything.
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Re: BBC rear main leak

Post by fastvette »

I use the one piece seals from Fast Fish auto parts.
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Re: BBC rear main leak

Post by AA Performance »

rebelrouser wrote: Thu Nov 17, 2022 6:11 pm Just from my experience you will be hard pressed to get a seal company to pay a big repair bill for labor. And as mentioned if you show them that picture with gobs of silicone under the seal I am sure they will not pay the claim. I have used a little silicone under the seal from time to time and the weight of the crankshaft should have pushed it down. I see a void under the seal. Which would maybe make it leak. Was the engine line bored? The only issues I have ever had with a chevy rear main leak is on engines that have been line bored. Felpro makes a rear seal just for engines that have been line bored.

As far as rear seals go I just pulled one out of an engine gasket kit for a SBC that I throwed away because of the way it fit. The quality of parts is getting to be a real problem, you have to double check everything.
If you click on the top photo, it should enlarge. You can see clearly that the edge of the seal that seals on the crank is gone. Looking at the seal when removed, it looks like the very corner of the seal is gone, almost as if it was hit on a linishing belt. When I smoke tested it , that was were it was leaking from that corner. It definetly looks like a fault in the seal and the silicon on the mating faces would have had zero efect. It even looks like the outer dustseal isn't even coming into contact with the crank. Totaly different to the second pic taken from the other side.
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Re: BBC rear main leak

Post by rgalajda »

Look at the arrows in the picture. Something wrong here? Is this a Fel Pro Viton seal?
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Re: BBC rear main leak

Post by rp930 »

With the seal pushed out from the silicone it may have worn it off. Looks like a sloppy install I’m sorry to say.
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