My understanding is that 351W blocks had 2 piece rear main seals until 1984 and that beginning in 1985, the blocks switched to the 1 piece rear main seal. Is this correct?
jbuening said: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.
jbuening said:The rear main seal goes in the block and in the rear main cap. Maybe you are confusing it with the rear pan 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?