Felpro 1 pc oil pan gasket question for SBC - Hot Rod Forum : Hotrodders Bulletin Board
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Old 12-30-2009, 07:29 PM
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Felpro 1 pc oil pan gasket question for SBC

Hi all. I have a Chevy 350 that I have the pan off to fix a dreaded rear-main seal leak. I have a Felpro 1 piece oil pan gasket (OS 34510T) to use when I reassemble. The question / problem that I have is that the end seal at the BACK of the gasket is much thicker than the seal that came out. I can make it fit, but is requires stretching it around the main cap quite a bit to make it reach the parting line. This doesn't seem right to me.

I realize there are 2 configurations of pan gaskets for SBC, but I believe the difference was the thickness of the FRONT seal, not the rear. I'm a bit confused. I always was only 1 thickness seal for the rear of the block.

The year of motor is a bit of a mystery. It is a 350 4-bolt main, 2 pc. rear main seal motor, block casting number 3970010. Based on the stampings on the pad at the front of the block it is either a 1979 or a 1970, but I have not been able to distinguish which. This complicates things a bit because the front seal changed from the thin to the thick style around '75. Both the pan and timing cover are generic chrome.

If worse comes to worse I will use a 4 piece gasket set so I can pick the end seals that fit the best and lots of RTV, but I would like to use the 1 pc if I can. The cost of buying the 1 piece thin gasket on a lark is a bit prohibitive. Has anyone run into this problem or have any great revelations? Thanks in advance!

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Old 12-31-2009, 12:53 AM
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CSB oilpan gasket + rear main seal

how would it be stretched like with wise? and try a difrent gasket maybe that one was off but other than that no advice sorry.
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Old 12-31-2009, 07:24 AM
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The one piece gaskets do have a bit thicker end seals, but I have never had a problem installing them. Follow the directions to the letter and do not get carried away with RTV or you will have leaks.

Vince
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Old 12-31-2009, 07:30 AM
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id only use sealer in the 4 corners
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Old 12-31-2009, 08:35 AM
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I have the same block (1979 3970010 4-bolt 2pc. out of a C-10) and same Felpro gasket. Also have a chrome pan, but an aluminum timing cover. No issues at all with the thickness of the rear part of the gasket. Nary a drop of oil out of it since assembly five years ago.

I cleaned all surfaces very thoroughly (lacquer thinner), especially the little nooks and crannies (technical term) where the block pan rails meet the front cover and the rear main cap. Put just a pea-sized dab of RTV into those crannies, then press the little nubbins on the gasket in there firmly. No RTV anywhere else. When the pan is torqued down (10-15 ft. lbs.) the rear of the gasket will compress and conform to fill the space between the cap and the pan very nicely. Them Felpro boys know how to make a gasket!
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Old 12-31-2009, 08:44 AM
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If your changing the rear seal you also need to apply just a smear of RTV to the rear main cap setaing area to the block...don't over do it.

Vince
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Old 12-31-2009, 09:42 AM
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Thanks for the advice!

Thanks everyone for the advice. I have confirmed that my motor uses the thick seals, but the new FelPro gasket is significantly thicker both front and back. I'm going to go for it with the new gasket, just a dab of RTV in the corners, and see how she goes. It'll be a few days before I get it back together, but I will post my results when I get them. Wish me luck!
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Old 01-07-2010, 10:13 PM
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Success - the new FelPro gasket is awesome

I had great success with the new rear main seal and the 1 piece oil pan gasket. Getting the motor back together took a few extra days because I ended up changing the main and rod bearings while I was in there. The crank looked great, but a few of the bearings had some scratches down to the copper so I went ahead and replaced them.

I replaced the rear main seals with the FelPro 2-piece blue silicon ones. No problems getting them in. I offset the ends of the seals from the main cap parting line by about 3/8 of an inch and put a light dab of RTV at the ends. I also put an extremely light layer of RTV at the parting line of the rear main to the block, plus a little bit along the horizontal chamfer where the cap and the block together..

XNTRCI-T - I cleaned everything carefully with lacquer thinner like you suggested (I'm familiar with the technical term nooks and crannies!), then put a pea sized dab of RTV in each corner of the block like you and Candy63 suggested. I deviated from the instructions and filled the unused (right hand) dipstick hole with RTV just in case.

Since I did this job with the engine in place, I used the "snap-ups" that thread into the 4 corners and hold the gasket and pan in place. Those worked very well - the only trick is to be sure to lube the plastic threads a bit because they are buggers to get out. I used assembly lube and I was very glad I did.

302 Z28 was right - even though the ends of the gaskets are thicker than stock (nearly twice as thick) but the scrunch down without any problem when the pan bolts are pulled up.

I ran the motor for about 45 minutes to break in the new bearings and watched for leaks. Spotless! XNTRCI-T is right - those FelPro boys definitely know how to make a gasket!

My biggest worry was the uncertainty of the year motor and whether I needed the thick or thin gasket set. Lesson learned - aftermarket (cheap chrome) T-chain cover and pan use a thick gasket and don't over think this stuff. A million hot-rodders must be right! Thanks guys!
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Old 01-08-2010, 09:31 AM
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Thanks for the update. I wish more people would do a follow up on their problems. It could help some of the rest of us.


454 RATTLER
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Old 01-08-2010, 10:03 AM
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Glad it worked out for you, thanks for the feedback.

Vince
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Old 06-09-2010, 10:28 PM
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correct installation of sbc 2pc. rear main seal !

What is the correct facing of the seals? Need a view sketch ! tThanks
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Old 06-10-2010, 12:30 AM
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Quote:
Originally Posted by mod
What is the correct facing of the seals? Need a view sketch ! tThanks
You just need to install the seals w/the inner lip towards the engine.

From HERE:


Last edited by cobalt327; 06-10-2010 at 12:40 AM.
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