[bigblockv6]

Originally Posted by hjennings

Net vs Gross horsepower. They used to measure the HP without the accessories, now they measure them with (that started that in '71 or '72 I believe).

Some of the specs are hard to find on these old engines. I've found some data on the heads that says the flow about the same as a 350 from that era. That sounds OK, except those flow numbers are total, and the V8 is split between 8 cylinders while our engines are only feeding 6 (so less flow per cylinder).

I said above I'd probably go with a 305E engine. My thinking there is it probably has the most flow per cubic inch of any of the GMC V6 engines. If somebody can confirm or deny this please let me know. I'm sure it'd be between a 305E and a 351E (Magnum heads). The 351 may be the one to use. Not sure until I find the flow numbers.

500hp is a complete wild *** guess. I hate evening saying that, as we have built several engines and can usually tell a customer what a certain combo will make and the dyno is always really close. With a buildup of a turbo GMC V6, it's never been done. So who knows. A big part of it is how much boost and how many RPMs the block/crank/rods can take. I'm guessing that these engines are very strong (as far as how much HP they can take.... they've never been tested at any sort of limits). So who knows, might be able to handle some insane boost levels.

The highest horsepower ratings on all GMC V6 engines were from 1966-71. They dropped in 1972 due to emissions and also gross ratings were no longer used that year.