The +0.250 BBC motors have been around in low deck versions for quite a while now, my first one was a 555 from Shafiroff back in 2002, it was one of their "pro series" motors. Made 1000 hp and 780 torque on a 355 pro 1 Dart head, was an awesome motor. It had the +0.400 longer rod with a 0.043" top, 1/16" second, and 3/16" oil control ring. Never had an issue with that motor was very consistent and easy on lower unit parts. At the time it used a "custom" Wiseco piston, now a days they offer this ring stack and dome configuration in their Q-16 pistons they keep on the shelf.
The wrist pin being in the oil control ring groove never seemed to be an issue except for the one time that the builder let the end of the oil control spanner/tension ring fall out in the center of the wrist pin. That resulted in the tension ring overlapping itself in the wrist pin hole and zero to very minimal tension on the oil control ring. Relatively easy fix, remove the piston, re-orient the oil control ring tensioner end gap to the correct location, and put it all back together.
If you pay attention during piston/ring installation, the 0.400" longer rod (6.535) should be a nice package in a low deck 4.250" stroke BBC.
IMO longer the rod the better assuming you can get the correct/optimum ring package you are looking for in your application. Piston dwell time helps, but as others have stated its not the end all say all and won't be the difference between your motor being a dog and one being the best ever. It could make a really good one a tad better if there's anything at all to this dwell time discussion.
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