[PanozDuke]

Kel,
I do have all the internals for a 347. I bought the Probe pistons that do not cause the pin to intrude into the oil ring groove, H beam rods and a forged crank. I haven't built it, but planned on making 400-450 hp at 6000 using a 5.0 block with main stud girdle. The compression would be about 10:1 with a good hydrolic roller cam with about .550 lift. The motor was going to be used in a 69 Mustang for street and open track. Since my power and rpm limit goal was modest, I felt the 5.0 block would be fine. They seem to be OK up to 400 hp without a girdle as long as you don't power shift them or get them too hooked up from a standing launch. With the girdle, I felt it would be solid for my occasional track use. With the kind of power you are going to be making, I would not plan on the 5.0 block standing up to that long term. My knowledge of the new Boss block versus the others is nil. I believe at least one of them has to be notched for rod clearance. I would be surprized if the cylinder skirt length were an issue in the Boss block since it was built with the idea of making a 342 stroker. I could be wrong and it also might depend on the pistons you use. Since I haven't built the motor yet, I can only tell you what my experience led me to do in terms of the concept.

The 331 vs 347 debate I really don't know much about either. Since I had a way to avoid the oil control problem with the 347 and my rpm and power limits were reasonable, I wasn't worried about the rod to stroke ratio and it seemed OK. What I wanted was midrange torque and 347 beats 331 in my book. If I were looking for a pure road race motor with more power, I'd probably up the compression and keep the rev's down so it would live a good long life. I'd get the strongest block I could find. That is probably not the new Boss block and the costs of the others isn't that much more. I think they weigh more than the Boss.

About the 331 crate with 500 hp: my bet is that it is a drag race motor with not much in the midrange. I'd want to see the dyno numbers. I think you could get 500 out of 331 in a road race power profile, but it would be fragile and you'd be reving it over 6500. Not so good for long life. What you really want is midrange torque not max rpm hp. If you want 500 hp, do the 351 stroker with the best internals and an aftermarket block and keep it at 6000. Maximize the midrange. I have to agree that the stock 351 block is very marginal over 400 hp, even with good internals.

Mike