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Exhaust is fine on peanut port heads.... if the intake doesn't even outflow a 283 head why worry about exhaust! All bbc are screw in studs or bolts, the vortec need tapped to 7/16 because the use a funky non adjustable bolt. The vortec bbc flows more than 150 but cant remember exactly what it was. About all the good sbc heads flow close on exhaust and vortec isnt the best flow but it has real good velocity and there is a ring under to valve job that if you go bigger valves you lose flow and velocity
When i go back to the shop ill post some numbers from a 402 headThar's one thing that Chevy got mostly right. The exhaust on BB Vortec are right massive.
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427 holds together better, rod angle is better and it has a really broad rq curve compared to 454 having a big jumo then dip in tq. They didn't make a tall deck 454 for heavy duty and did a 427... ever wonder why?Why the hell would you wanna build a tow motor, and make it a 427?!? Sorry but that’s ****** stupid. 427s are a higher RPM motor, and hi RPMs are pointless when towing. If you do a basic rebuild on the motor, mild cam, and a good tune, it will wake it right up. Like I said before, I had a 97 with the 454, would smoke the tires from a stand still, and would pull like a dream. This was a 99.9% stock truck, think I had a K&N filter and true dual flows going out the back.
The conversion ones work but thats were weak point will be. Only option if heads are still on engineComp sells a conversion stud to run standard big block rockers with the vortec heads.
https://www.summitracing.com/parts/cca-4514-kit