convert 2 peice rear main to 1 piece?

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I sell CNC machines for a living so getting the block machined will cost me nothing. Just can't find out if it is possible with out weakening the back cap to much. I have replaced the seal 3 times and can not get it to stop leaking. I have checked everything else as the source of the leak and it comes down to the rear main. Is there a slinger on the crank of a older 302 that may not be on a aftermarket stroker crank?
 
I sell CNC machines for a living so getting the block machined will cost me nothing. Just can't find out if it is possible with out weakening the back cap to much. I have replaced the seal 3 times and can not get it to stop leaking. I have checked everything else as the source of the leak and it comes down to the rear main. Is there a slinger on the crank of a older 302 that may not be on a aftermarket stroker crank?

Yes, the stock crank has a slinger. Were your three seals neoprene?

The ridge on the far left is the slinger:

1M_01.JPG
 
Yes, all three were FelPro Seals. Do the 1 piece cranks still have the slinger? If not then I would guess that most of the aftermarket strocker cranks would not have the slinger. This may be the problem.
 
No slinger on the 1 pc cranks. The knurling there also keeps the excess oil away from the seal as well. You might also consider the possibility that you've got too much oil in the pan too. I've had that problem with my 331 and the aftermarket pan I've got on it now. It was advertised as a 9 qt' pan, but try running anything more than 8 qts and it'll weep oil out both the 1 pc seal and the end radius's of the pan. The one piece seal, seals no better than the 2 pc.
 
If you having problems with a two piece, check to make sure the thing isn't two big. Have seen instance where when you install the seal into the block, then just lay the other side on the crank, the damn thing is too big. I clip about 1/8 of or what ever it needed to make it seat correctly. I left enough on there so it still did compress. You can, not see it, torque it down and the torque wrench will still click. It gets nice and tight, but doesn't seal.