rear main seal question

the oil pan doesn't care what kind of rear main seal you're running.

If you want a leak free one, order the Felpro one piece gasket made for the early mustangs. It's around $50 but well worth it IMO. It is a rubber composite with a steel core and leak free performance. Reusable too and no RTV required!

Also, the type or rear main doesn't affect the pan gasket. BUT, the year of pan does. The early pans had ribbing in the pan flange to prevent the cork from squeezing out. The later 5.0/5.8 engines had flat flanges, thus the gaskets are different. Felpro makes a specific gasket for the early pans (early i mean pre 5.0) and is available at autozone. I know you aren't running a 5.0 pan (cause it is rear sump) but they may try to give you a 5.8 pan gasket.

The rear main seal goes in the block and in the rear main cap. Maybe you are confusing it with the rear pan seal?

Isn't the rear main seal for a 351W a bigger diameter than a 302? So the pan gasket should be ordered for a 351W and not just for a small block Ford like "Jegs" advertises. Aren't the pan gaskets different between a 351W and 302, but the rear main bearing cap is the same Outside diameter on a 351W between a one piece seal and a two piece seal?

thehueypilot said:

Isn't the rear main seal for a 351W a bigger diameter than a 302? So the pan gasket should be ordered for a 351W and not just for a small block Ford like "Jegs" advertises. Aren't the pan gaskets different between a 351W and 302, but the rear main bearing cap is the same Outside diameter on a 351W between a one piece seal and a two piece seal?

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Crank and the rear main seal for a 351w is larger than a 302. Needs a 351 specific part, a 302 won't fit. Doesn't matter it you are talking 1 pc or 2 pc seal--both are larger than the 302 counterpart.

The rear main cap is also physically larger than a 302, so a 351w will only work with a 351 pan specific gasket. Even the oil pan is 351w specific to clear the larger rear main cap needed to clear the larger crank.

I had both my old 69' block and 89' block setting side by side during my build. jbuening is correct that the block sealing surface has not changed over the years. I believe that 1983 is when the 1 pcs seal appeared in a 351w.

I used an SCE 1 pc rubber oil pan gasket that Summit sells to install my 69' 351w oil pan (original 2 pcs seal block) on my 89' block (1 pcs seal.) Seals perfectly, no issues. It is very pliable rubber and I know it would be hard to install from under the car, but on an engine stand it was a piece of cake. Had I know then the differences of the pan, I would have went with a 1 pcs oil pan seal for a 2 pcs seal block.

To sum it all up for Jerry, if you are truly concerned, choose a pan gasket (any pan gasket) made for a 2 pcs seal (such as your 69' block) and install it. It will work an your later year block and be the best choice for the oil pan that you have. The 1 pcs pan gasket has an edge over the "multiple" pcs ones for sealing.