I have read that people are seeing increases with using smaller rod and main bearings.. I've heard of some people having their rod journals ground down to acura bearings or so to reduce frictional drag.. With that theory in place would it substain to say that a dart little M block with 400 mains and a 3.875 stroke would have more friction than a Dart little M block with 350 mains because the 350 mains are smaller and I might just free up some frictional hp loss?

Kevin

 

I'd guess that it's pretty give & take, less friction but more psi on the smaller bearing, it's likely it'll wear out faster and probably wouldn't hold too well at higher RPM. Personally I'd trust the designers of the block and crank, they've calculated the forces and friction in all this, good enough for me.

 

From what I hear a lot of the premier engine builders do this, smaller bearings are good to a point, it does free up a few extra hp, but for a street engine I don't think you would see any real difference, the smaller bearing runs at less feet per min., so that offsets the wear factor. As far a strength goes the manufactures over build most stuff so it don't hurt the strength much to turn it down some if it's done correctly with the large radius in the corners.

 

But they offer both 350 mains and 400 mains which would probably be better?

 

I would go with the 350 mains. But who ever you buy the block from should be able to give you the pro's and con's of each.