Ill wait till winter....I will be busy come November, hopefully rebuiling a miata and the boat motor

The thru prop Alpha exhaust supports 300 horsepower. If somebody was running a 330hp 454 thru an Alpha (and some are), I'd tell them to go to thru hulls for some free horses.

If somebody is running a 205 horse 6-banger, I'll tell them that they'll see no appreciable performance benefit from thru hulls besides the "louder is faster" phenomenon (automotive equivalent: 4 inch fart pipe on an otherwise stock Civic).

Headwork, cam, intake and carb can deliver another 30 to 40 horses pretty easily. Even with that in the bag, you're not crippling yourself with the thru prop exhaust.

If you're looking for the LAST mph, then do it. If you're looking for the FIRST mph, it aint the answer.

I try not to get into this kind of discussion,but I just couldn't help it.We see on SBC 2-3mph gain with thru-hulls only.And the drive runs cooler.

Okay, so how do we interpret that data into useful stuff for a 4.3 V6?

If a 300 horse 5.7 picks up 3 mph (I'm rounding up), then does that mean that a 200 horse 4.3 picks up 2, and a 120 horse 2.2 picks up 1?

OR does that mean that the 300 horse 5.7 picks up 3,
The 220 horse 5.0 picks up 1, the 200 horse 4.3 picks up a tenth of a mile an hour, and the 120/2.2 picks up nothing?

Does anybody have valid data on a 4.3 for Tommy?
He doesn't want to listen to the (non reversible) thru hull job if it's not going to speed him up.

He will gain nothing by going to thru hull exhaust on the 4.3 V6 in stock form.