SB thin and thick oil seals

brti · May 09, 2007, 09:47:51 AM

could anyone tell me the year they stopped using the thin front oil seal on the chevy oil pan and went to the thick one? Had a friend ask me and I'm dammed if I can remember.

enjenjo · May 12, 2007, 10:24:07 AM

I can't tell you exactly, but it was about 75. I ran into that problem changing the engine on a pickup. 73 engine into a 75 truck.

1FATGMC · May 12, 2007, 11:41:02 AM

Don't know if this will help him or not, but this is out of HOW TO REBUILD YOUR SMALL-BLOCK CHEVY by Vizard.

First you have to have the block to pan gaskets in place. When I did this and in the picture the motor is on an engine stand upside down. Also the front cover is in place (timing chain cover). If a 0.006 to 0.010 feeler gauge will slip past the front cover, under the lip of the pan and into the crankcase area, then you need the thick seal. If your pan won't pass this test then use the thin seal.

You push the feeler gauge through at the lowest part of the pan directly under the crank or above it depending if the engine is upside down or right side up.

The gasket set I had came with both seals. Don't ask me which one I used as I already forgot :cry: .

c ya,

Sum

Dave · May 13, 2007, 08:07:38 AM

Years ago we bought a new oil pan for the sprint car i was wrenching on and the guy had a low drag racing style pan on it

Ya that lasted a long time. We got a nice oval track pan from speedway and had one night to get it on the car and the car all back together to go racing the next night right after work.. Hummmm its like 7pm the new pan takes the thick seal and we have a thin seal.. The car owner is * and wants to go racing and askes me what we can do :?: Well i looked at the difference in the radius from the old pan to the new pan and grabbed the torches and some brazing rod. When i got a nice bead all brazed on i let it cool and grabbed my die grinder and a file and smoothed it out and cleaned it really good and we put er on.... Worked like a champ and never a leak...
Dave

Bruce Dorsi · May 13, 2007, 11:02:04 AM

Quote from: "brti"could anyone tell me the year they stopped using the thin front oil seal on the chevy oil pan and went to the thick one? Had a friend ask me and I'm dammed if I can remember.

The thin (1/4") seal was used on '55-'75 engines.

The thick (3/8") seal was used on '76-'85 engines.

HOWEVER, the thickness of the seal depends on the front timing cover and the oil pan being used, NOT the year of the engine block.
......The timing cover should match the oil pan.

Measure the oil pan from its mounting surface to the bottom of the arc where the seal fits. .....It it measures 2-1/4" it is an early-style pan. .....The late-style pan measures 2-3/8".

Early-style front covers had the timing tab welded on.

Later-style covers used bolt-on timing tabs.

brti · May 14, 2007, 04:05:54 AM

The seal I'm referring to is about 1/2" to 5/8" thick. It sort of "wraps around the lip of the pan. The motor is a 327 with aftermarket timing cover and pan. I've got the normal "thick" seal in but there is still about an 1/16-1/8 inch gap between the pan and the cover.
Next move is to chuck the works in the dump and order a matched set from some one,,,,,,,, any suggestions?

enjenjo · May 14, 2007, 09:13:53 AM

Make a shim out of 1/8" aluminum, glue it in place with Ultra Blue Silicone sealer

Bruce Dorsi · May 14, 2007, 11:09:23 AM

Quote from: "brti"The seal I'm referring to is about 1/2" to 5/8" thick. It sort of "wraps around the lip of the pan. The motor is a 327 with aftermarket timing cover and pan. I've got the normal "thick" seal in but there is still about an 1/16-1/8 inch gap between the pan and the cover.
Next move is to chuck the works in the dump and order a matched set from some one,,,,,,,, any suggestions?

I believe you have a mis-match between the cover and pan.

You can measure the pan as I described above, and then get a matching cover. .....Or, you can make a spacer as Enjenjo suggests.

Dave · May 14, 2007, 11:13:43 AM

Quote from: "enjenjo"Make a shim out of 1/8" aluminum, glue it in place with Ultra Blue Silicone sealer

Or the brazing rod trick...
I agree with Bruce thats an awful big gap. Something is miss matched
Dave

reborn55 · May 15, 2007, 11:28:18 PM

Don't know if this is true but I have heard that the 400 sbc had a different timing cover and or oil pan which could be a mismatch somewhere down the road.