Author Topic: 396 engine rear main seal replacement  (Read 337 times)

monaroman

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396 engine rear main seal replacement
« on: August 05, 2018, 07:36:22 AM »
Hi,

Has any members replaced a leaking rear main seal whilst the engine is still in the vehicle?

If so what was best procedure?

Thank you

bcmiller

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Re: 396 engine rear main seal replacement
« Reply #1 on: August 05, 2018, 01:53:30 PM »
Do you have a lift? 
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cook_dw

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Re: 396 engine rear main seal replacement
« Reply #2 on: August 05, 2018, 06:36:54 PM »
Pull the engine.  By the time you try lifting the engine up, rotating the crankshaft so the rods and throws allow the oil pan to drop you might as well pull the engine.  I had the same issue with a previous car.  Debated what to do and just pulled it.  While it's out check out everything else since you have the opportunity.  But I'm sure you will get other opinions.  Also use a one piece oil pan gasket.  Tip for the rear main - offset the parting lines of the seal and the cap & block and use RTV on the cap & block mating surfaces.
Darrell Cook


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bcmiller

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Re: 396 engine rear main seal replacement
« Reply #3 on: August 05, 2018, 06:44:55 PM »
I agree. Pull it. It will result in fewer potential problems. Then you can clean/detail the engine and engine bay. 

Have done it before - but it is a real PITA.  The only way I would even consider it is if you have a lift.
« Last Edit: August 06, 2018, 04:43:32 PM by bcmiller »
Bryon / 1968 Camaro SS 396 coupe - now 468 cubic inch BBC/M21
67 RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016

69z27z87

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Re: 396 engine rear main seal replacement
« Reply #4 on: August 06, 2018, 04:41:06 PM »
one other big tip....when you install the new seal in the cap and block, push the seal flush with one side and measure how much it sticks up on the other side. There is a spec for this measurement....both on the cap and the block...(I think I have it in another posting).  most seals are TOO BIG out of the package and you have to file them down.

Being too big, they overcrush and distort when the cap is reassembled. Then it leaks... how do I know? 3 seals installed fresh from the package... 3 leaks... one installed and then measured and filed down as needed.... does not leak.
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monaroman

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Re: 396 engine rear main seal replacement
« Reply #5 on: August 06, 2018, 11:02:30 PM »
Good morning,

Thank you to all you fellas who replied.

Some really good experience there and I shall follow the suggestions.

Winter here so might wait for it to warm up a little.

Oil leaks are annoying and don't really want it to cause issues with my clutch etc.

Once again thank you for the advice.

Opium Motors

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Re: 396 engine rear main seal replacement
« Reply #6 on: August 08, 2018, 02:00:07 AM »
I have replaced several without pulling engine. Basically remove cap, snake out upper seal, snake new seal in, replace cap, RTV. Corners, boom your done.

PS the above is not for the “Rope Type” seal but rather the rubber style.
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Kelley W King

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Re: 396 engine rear main seal replacement
« Reply #7 on: August 08, 2018, 11:25:18 AM »
I think the seal procedure is the same in or out on an assembled engine. It is getting the oil pan off and on that is the real b-t--. I did a pan swap (no seal) and should have pulled the motor. Some cars the pan drops off. Some cars fan shroud, hoses, exhaust bolts, motor mounts, ect. Then the motor is just sitting there.
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monaroman

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Re: 396 engine rear main seal replacement
« Reply #8 on: August 09, 2018, 06:45:56 AM »
Hi,

What is the best seal to use for the rear main seal?

1 peice sump gasket?

Talking to a couple of mechanics who say rope always leaks slightly?

I guess follow instructions with installation with clocking or RTV.

Thank you.

Opium Motors

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Re: 396 engine rear main seal replacement
« Reply #9 on: August 12, 2018, 09:07:09 PM »
Rope seals have to be trimmed, if done improperly it will result in a leak.

Also, be careful with the RTV, I bought my 73 Vette 454 cheap because they thought the motor was going out for it showed very low oil pressure. Brought the Vette, pulled pan and main cap, all looked fine. Replaced oil filter but first pulled screen. Come to find out, the screen was filled with RTV and restricting oil flow. Cleaned screen and oil pressure was perfect.

So be careful very careful when using sealer.
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monaroman

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Re: 396 engine rear main seal replacement
« Reply #10 on: August 13, 2018, 09:25:59 AM »
Hi,

Yes, that silicon sure can get in and about the engine if over used. I believe the Felpro #2918 calls for a slight dab of silicon.

The Felpro #2918 seems to be the best suited rear main seal for my 396. 1 peice sump gasket also.

Has anyone had any issues using the above seal?

Thanks for your input.