tonawanda 454 performance upgrades ???

tri5ron · June 5, 2004

Hi, I new to this forum, my name is Ron,

I have a 1991 GMC 3500 Van, with the Tonawanda 454 engine, and 4 speed O/D tranny. it is bone stock and runs well but the van seems to not have the asphalt ripping power that I remember in my moms old '76 Caprice (carburated 454).

The van has nice bottom end and towing power, but dosent seem to have the passing gear and/or upper end power that I would expect from a 454.

also after reading and old posting here, about the HP only being 255 on the SS model trucks, I was a bit shocked that it was so low.

now I realize that I've probably got smaller valves than mom's old Caprice,

(boy I sure did love getting to take her car on a date, rather than dad's Vega wagon),Ha-Ha!,( but that was quite a few years ago...),

but does anyone have any suggestions asd to how to squeeze a few more ponies out of this thing without having to do a major build? is there any decent computer chip mods? or not too expensive other ways?

I dont want to do headers simply due to the inherant heat/leak problems, (especially the heat under such a small engine cover/doghouse), but I might be open to a dual exhaust idea.

I'm not looking to drag race, (afterall, this is a Daddy-Wagon window van with kiddie seats in the rear), BUT, I just want to get a little more of a smile on my face when I go from the onramp to the fast lane...

any suggestions? Thanks in advance, Ron

snoman · June 5, 2004

That is a TBI unit and it does not flow very well above 3500 rpm or so and power falls of rapidily. A larger TBI throttle body unit with a better intake would wake that beast up a bit. So would a nice flowmaster added to it. Do this and you should get well into the 300hp range. Through in some headers and pick up another 20 to 30 hp. The old big block responds quit well to breathing improvements as it is very choked off in its stock state!

Butch 02 Denali · June 6, 2004

The "peanut port" heads, small valves and small cam all add to the power drop off at 3500 or so. This is a torque engine tuned for low end grunt. I have a 1990 454 that I plow with a 9' Fisher blade, great plow truck! I have done a Flowmaster 40 series exhaust with a high flow cat, added a K&N filter, replaced the intake tube and added a Hypertech chip. It all helped a little but hardly noticable, though it sounds good! My buddy has a 454SS. 3 years ago we tore it down and put a set of oval port heads and a decent street cam in it with new timing chain. Everything else was stock. WHAT a difference!!! Felt like it gained 50 HP!

Butch 02 Sierra Denali

snoman · June 6, 2004

THis is very true that there is a lot of choke points but with a upgrade manfold and bigger TBI throttle body even with small port heads it will wake up and pull past 4000 or so and a lot stronger. I had a few big blocks from early 70's to early 80's. I really loved the smoothness and torque of those babies!