Thread: 7.4 L 454 EFI Gen V performance increase

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Noob to this forum. I have a 1990 GMC K3500 Dually that seems a under powered when I'm pulling my 40' 5th wheel. I've been trying to find info on how to perk it up some. I'm thinking: headers, dual exhaust, hi-output coil and a spacer between the throttle body and manifold. Currently, the engine is bone stock and runs good. I looked up the output: 230 hp / 365 ft/lb torque. Does anyone have experience with this 454? Can you make recommendations? What kind of increase am I looking at with the above mods?

Any help is much appreciated.

Thanks,
MoralDK

Welcome to CHR! Pat McCarthy is our resident BB expert - none finer - if it's been done, he's done it more often and better than anyone. He will be able to give some good advice about most anything aftermarket or internal for big blocks.

With my "limited" experience I'd recommend that you first make sure that any modifications you make will stand up to emissions laws. Washington State requires emissions testing every 2 years and I believe Spokane County is included.

GM has done a pretty good job of compromise with mileage/performance and "noise" on the big dogs. What you can do is performance intake, such as K&N (7 horsepower) and a cat-back exhaust from Gibson (5-10 horsepower). Both companies meet CARB requirements which Washington recognizes as emissions compliant. The intake in particular will give a noticeable bump as it removes the stock air filter housing and you're no longer sucking air through a tiny little funnel.

The throttle body and MAF sensor are two more components that may have a few horsepower hiding in each of them but make sure the throttle body is compatible with your cruise control. Key for the MAF is overall air flow. Granatelli make a high quality replacement that flows 60% more over stock that may add 8-15 HP.

So - with "bolt-on" components that won't violate your emissions laws you can get 20-45 HP or so.

You may also be able to tweak your computer programming to raise the shift points allowing you to better utilize some higher RPM when towing.

Good luck and once again, welcome to CHR,
Glenn

well you could put a whipple supercharger and it will pull and pull.... a customer had one on a 1990 chevy in time i built him a engine for the wipple he order the smallest pulley for the blower and was at 10psi of boost it was fun .the bad news is whipple will not build you a kit for the 1990 truck . you may find one used on e bay ? before you buy one used call whipple see if they will rebuild the blower . what glenn said would be good start .i would look at a big bbc like 496 or bigger 512 .if yours is in good shape you could do the top end and cam . but if you go that far i would make it bigger in CID

I could be wrong but, I do believe Holley sells a throttle body that acheives some pretty decent gains in HP and T. (and even 1mile per gallon MPG increase!)

trade it for a ford 7.3 or a dodge cummins---or sell the trailer

Several years ago I swapped out my TBI 454 in an 89 V-3500 for the HT502. Best thing I ever did. It would pull and pull and ran on pump gas. The downside is it cost around 6k for the motor from GM. The best it would do for fuel mileage was 9mpg. I ran summit headers on it, an edelbrock 1407 carb on an air gap intake, jacobs ignition and rapid fire plugs. I had a friend use edelbrocks multipoint conversion for the tbi and it ran great and pulled real well for what he was using it for.
40 feet of 5er is alot of weight, have you considered swapping to 4.56 gears in the rearend and using a gear vendors overdrive to split the gears and still have a decent cruise rpm?
Good luck and keep us posted on how it turns out.