454 (7.4L) swap / repair options - 1999 Suburban K2500

[Mangonesailor]

MoAr data: https://www.chevelles.com/threads/l-29-heads-actual-flow-numbers-stock-vs-ported.248642/

 

[b454rat]

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.

 

[L29Sub]

Thar's one thing that Chevy got mostly right. The exhaust on BB Vortec are right massive.

Sent from my SM-G965U using Tapatalk

 

[Christian Steffen]

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

Comp sells a conversion stud to run standard big block rockers with the vortec heads.

https://www.summitracing.com/parts/cca-4514-kit

 

[Christian Steffen]

So I remember reading that FSC thread back in the day.. was he claiming whp/wtq or flywheel? The HP seems quite reasonable at flywheel, the torque sounds inflated to me but i could be wrong. The 493/609 with some boost sounds perfectly reasonable IMO.

 

[badco]

Thar's one thing that Chevy got mostly right. The exhaust on BB Vortec are right massive.

Sent from my SM-G965U using Tapatalk

When i go back to the shop ill post some numbers from a 402 head

 

[badco]

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.

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?

 

[badco]

The reason the performance 427 was considered a rpm engine was the power was made up high because of the rectangle port heads. The rectangular port heads flowed massive air and hurt bottom end alot

 

[badco]

Comp sells a conversion stud to run standard big block rockers with the vortec heads.

https://www.summitracing.com/parts/cca-4514-kit

The conversion ones work but thats were weak point will be. Only option if heads are still on engine

 

[b454rat]

The 427 tall deck had a heavy ass rotating assembly, really only the pistons but had a huge flywheel too, that translates to torque. I’ve never heard anybody build a 427 for torque. The heads sucked on TDs, maybe cause a 454 needs more air they opted not to build one.