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1 piece vs 2 piece rear main seal

38K views 15 replies 10 participants last post by  sbc1320 
#1 ·
Wondering what's the difference between the two? How can I tell what I have? Running a GM 350. I'm planning to switch out my rear sump oil pan to a front sump. Thanks!
 
#7 ·
#6 ·
I dont think there is a one piece front sump pan available so pray for a 2 piece motor.

This is how to tell, a 1 piece motor has a completely round flange and the seal rides on the perimiter of the flange. A 2 piece seals on the rear bearing journal and the flange is not completely round unless you have a pre 68 small journal motor.
 
#9 ·
Front sump 1pc rear main seal pans are indeed available. Chevy2only sells them, and I'm other large Nova parts vendors carry them too.

The biggest difference I found, when I accidentally got shipped a 2pc pan instead of a 1pc seal pan was that the rear seal area was much larger in area than the 2pc, so there was a bigger cutout in the rear of the pan where it goes around the rear crank flange.
 
#8 ·
If thats the generic low HP replacement motor then it is a 2 piece rear seal, at least the one i bought new was a few years ago. They also have a dipstick pad on both sides but the pan will seal with enough silicone:)

Do an internet search with that part number, it will come up and probably answer your questions.
 
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