I've had both on my boat motors and can't say I could tell the difference with the same boost levels.

I'm not sure if the 8-71 will produce less heat than the 6-71 at the same boost level. It's the compression of the air that creates the temperature rise and the required horsepower drain from the crank, although there might be a few second order effects like windage and frictional losses involved. You'd probably need a dyno to see these slight differences though.

The Littlefield blower I'm running on my present boat came from a friend who replaced it with a brand new 8-71 from Summit. After $3500 and 2lbs more boost his boat ran the same speed.

If you're running oval port heads on your 454 the 6-71 will produce more flow than your heads can accomodate. You can end up building big boost numbers in the manifold plenum, but not making any additional power.

As stated the first number indicates the number of cylinders, the second the displacement of a single cylinder (and the engine series). Two stroke Detroit Diesels were offered in 53, 71, 92, and (I believe 121) Series. The 53 Series blowers were the basis for the small B&M blowers.

Regards, Mark