TBI, Vortec, 6.5…. or LS?

[MILLCMACK]

About a month after I worked the kinks out of the new transmission (from GM) I threw a rod in my 96’ k3500’s 454. Shopping for a new power plant I am having a hard time investing in a motor that has just never blown me away. Rebuilding quotes are close enough to reman crate quotes that it’s become a bit of question. I LOVE the TBI in my 94’ c3500hd and the 6.5 in the recently purchased 99’ c3500HD. They both tow very smoothly without as much pedal work if that makes sense.

These are 100% work/tow trucks, with 90% of the towing done in-town at 35mph and under. I do a little highway towing and would do more if the trucks liked being loaded and going 70 more.

Monthly maintenance and $$ invested for swap aside (I’ve already hitched myself to this clean, California body/frame and transmission lol) - what would be your recommendations or thoughts on repowering this truck?

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[L31MaxExpress]

Vortec 8100 would be my option. The shear abuse that engine can handle is mind boggling. I have a family member that has several setup for pumping water. The bottom end on one had 30,000 hours on it running 1,800-2,000 rpm at ~3/4 load. It has a had 3 or 4 sets of heads because Propane is not nice to the valves or seats and has eaten 2 cam and lifter sets (the rollers eventually wear and score up the cam), but the bottom end has the equivalent of towing a moderate sized trailer at 70 mph for 2,100,000 miles. At 30K hours the rods and mains were cut 0.010/0.010, it was honed, received stock replacement pistons, another set of worked heads, and a new cam and lifter set. Will probably work 10K hours before it needs anything again at which point it will be heads again. The cam and lifter set is now done as prevenative maintenence when the heads are done. With electricity rates it is more cost effective to run a big block or two on LPG even with the maintenance factored in than electric pumps, plus the reliability is higher than the grid with the random brown outs during summer.

 

[Drunkcanuk]

"Everyone" says the LS platform doesn't really "get going" until the RPMs are up above 4-5k.
If you are using these for work and not toys, I would probably stick with the TBI and get a new short block and toss it in.

 

[L31MaxExpress]

"Everyone" says the LS platform doesn't really "get going" until the RPMs are up above 4-5k.
If you are using these for work and not toys, I would probably stick with the TBI and get a new short block and toss it in.

I have found that exact statement to be true. Have to rev them up to 4,000 rpm before they really start to make any grunt. Comparing a similar 6.0L to a 350, the 350 has far more grunt under 3,500 rpm. It takes a LY6 with variable cam timing to somewhat keep pace with the 350 under 3,500 rpm and the 350 is still stronger. A 383 or 454 makes far more torque under 3,500 and an 8100 is a beast compared to those.

 

[Drunkcanuk]

I have found that exact statement to be true. Have to rev them up to 4,000 rpm before they really start to make any grunt. Comparing a similar 6.0L to a 350, the 350 has far more grunt under 3,500 rpm. It takes a LY6 with variable cam timing to somewhat keep pace with the 350 under 3,500 rpm and the 350 is still stronger. A 383 or 454 makes far more torque under 3,500 and an 8100 is a beast compared to those.

I'm still having the debate on what route I wanna go when I eventually do an upgrade to mine. But what I DO know is that it's a 6.0 or bigger if I go the LS route. Wanna get going fast instead of going fast. But mine is a toy.
For the OP, I like @L31MaxExpress suggested 8.1 route. If only so I can follow along for tips!! Lol

 

[Supercharged111]

I don't understand how a TBI 454 makes you happy but a Vortec that runs circles around it comes up short? I'd just do another 454 Vortec, give it a little more cam, freer flowing exhaust, and a tune. The tune alone is gonna wake that truck up in a way you can't imagine.

Another thing is the throttle body has a progressive linkage on the 454. You could bolt on an LS throttle body with a linear linkage.

 

[L31MaxExpress]

I don't understand how a TBI 454 makes you happy but a Vortec that runs circles around it comes up short? I'd just do another 454 Vortec, give it a little more cam, freer flowing exhaust, and a tune. The tune alone is gonna wake that truck up in a way you can't imagine.

Another thing is the throttle body has a progressive linkage on the 454. You could bolt on an LS throttle body with a linear linkage.

That was another trick of GMs to detune the off-idle throttle response of the older engines, similar to the lip used on the older vortecs like the 350. The later TBIs, TPIs and LT1s also had a progressive linkage on the TB. The earlier TBIs and TPIs used a linear linkage. The lip on the Vortec 350s changed with time and perhaps application as well. The TB on my 99 Tahoe had 2x the lip as the one on my 97 van. GM has also been known to pull timing out of the tuning to tame the off-idle, high load torque spike. The Tahoe tune had as much as 8* less timing as well in places. When the Vortecs first came out, the GM documentation video they made was really stressing to the delerships to try to push the L30 305 in place of a 5.7L. To a certain extent GM was accurate, towing a 4,000 lbs trailer a 96 1500 5.0L would out accelerate the older TBI 5.7L up a 20+% grade. Would not surprise me at all if by 1999 GM was trying to make the L31 feel less powerful to push the newer 5.3L trucks that had much less low-end torque.

 

[Caman96]

I don't understand how a TBI 454 makes you happy but a Vortec that runs circles around it comes up short? I'd just do another 454 Vortec, give it a little more cam, freer flowing exhaust, and a tune. The tune alone is gonna wake that truck up in a way you can't imagine.

Another thing is the throttle body has a progressive linkage on the 454. You could bolt on an LS throttle body with a linear linkage.

…and it’s already(1996) set-up for another Vortec.

 

[454cid]

Find a used Vortec 454, or get one built. A TBI will be down on power, and require an electronics retrofit to run it. An 8.1 will be up on power, but need an eletronics retrofit to run it. A 6.5L diesel is not practical due to reliablilty issues, in my opinion.

 

[0xDEADBEEF]

I felt the same about the Vortec 7.4 that I owned, underwhelming. The folks here say you have to rev up the 6.0 to make power, but at least it makes power somewhere.

Still, if it was my truck that I only used around town for work, I'd probably just take the easiest path which is another Vortec 7.4.