Help! Need More Power In 4.3 90 Chevy 1500

Old Chevy Guy · 10-10-2007, 07:09 AM

I need some advice from you engine guru's. I completely renovated a 1990 Chevy 1500 short bed truck. It has new paint, seats, carpet, bumpers, grille, headlights, taillights, etc. I purchased this truck to "fix up" for my son. It had a stock 4.3 "pre vortec" motor that was blown. It also had a auto tranny. I found a factory rebuilt 4.3 long block at a good price and replaced the engine. Now after completing the truck renovation and putting it on the road, I am disappointed in the horsepower. Having never owned a 6 cylinder truck in my life, I did not know what to expect beforehand. Anyway, I have spent so much money on this truck now, I need to find someway to get more HP out of this 4.3 motor. I have thought about putting street legal headers and replacing the ECM Prom with a hotter chip. Any suggestions on beefing this motor up without replacing it with a V8. Also, would upgrading the stock torque convertor give it more torque?
Thanks for your suggestions.....

tjzz4 · 10-10-2007, 07:18 AM

Change the rear end gear ratio to a lower gear...

75K30 · 10-10-2007, 08:18 AM

a 262 gas engine with 9:1 compression (pre votec) was making a little bit over 120 hrseower. Chasing bigger horsepower numbers are going to be unrealistic at best. Even if my numbers are conservative, you would have to find a "magic bullet' that could produce at least a 100% increase in power.
Later model vortec's with better heads and roller cams and central port injection (W code vortec's) could make as much as 170-180 Hp. This is gonna require a bunch of modification. With that comes money. In this case the least expensive option would have been a lerger displacement engine.
Changing the torque multiplier (converter) can be done, but is going to require compromise. This compromise is going to be a slightly higher stall speed. Higher stall speeds will equal more heat in the transmission, and more heat equals less transmission life.
tjzz4 provided great advice, that is often overlooked. Changing the gear ratio in the axle will provide a guaranteed increase in performance, by creating a mechanical advantage.

97SierraStepSde · 10-10-2007, 10:44 PM

where as changing the gearing will get u off the line faster (it has a 3.73 right now, or atleased my 97 did. almost guaranteed) ur only option from there is a 4.11. and gears run pretty tall 4 just a low end adjustment. I would **** can that whole thought. Find a buyer for the motor, strip it out and find either a nice cheap 350(about 280hp is the cheapest I found from Summitracing.com)or go 2 a local shop and see if they have anything like a 355 or something. Theres a place here(AZ)that has turnkey 355s for somethin like 3k or so. Mods wont be much besides different motor mounts. But good luck on ur decision and finding everything u need.

Old Chevy Guy · 10-11-2007, 06:08 AM

Guys, I appreciate all your suggestions and I think I already knew the answer in my mind. I made a mistake in putting the 4.3 motor in this truck. I could probably "doctor up" the motor and get a few more "hardly noticeable HP but, I would spend $500 to $1000 doing that and still would have a "weak engine" for a full size chevy truck. Would work great in an S10. I guess I was hoping for some magic. I can sell this 4.3 with less than 500 miles on it for $800-900 and put $1000 with it and drop in a 350 like I should have done at the beginning. The only questions I have is:
1. Will I have to change out the wiring harness?
2. Will I have to change out the ECM or just the prom?
3. Will I have to rework the emmission control & map sensors, etc?

Thanks again for your help...

10-10-2007, 07:09 AM	#1
Old Chevy Guy Junior Member Join Date: Oct 2007 Posts: 2	Help! Need More Power In 4.3 90 Chevy 1500 I need some advice from you engine guru's. I completely renovated a 1990 Chevy 1500 short bed truck. It has new paint, seats, carpet, bumpers, grille, headlights, taillights, etc. I purchased this truck to "fix up" for my son. It had a stock 4.3 "pre vortec" motor that was blown. It also had a auto tranny. I found a factory rebuilt 4.3 long block at a good price and replaced the engine. Now after completing the truck renovation and putting it on the road, I am disappointed in the horsepower. Having never owned a 6 cylinder truck in my life, I did not know what to expect beforehand. Anyway, I have spent so much money on this truck now, I need to find someway to get more HP out of this 4.3 motor. I have thought about putting street legal headers and replacing the ECM Prom with a hotter chip. Any suggestions on beefing this motor up without replacing it with a V8. Also, would upgrading the stock torque convertor give it more torque? Thanks for your suggestions.....

10-10-2007, 10:44 PM	#4
97SierraStepSde Senior Member Join Date: Nov 2006 Posts: 106	where as changing the gearing will get u off the line faster (it has a 3.73 right now, or atleased my 97 did. almost guaranteed) ur only option from there is a 4.11. and gears run pretty tall 4 just a low end adjustment. I would ** can that whole thought. Find a buyer for the motor, strip it out and find either a nice cheap 350(about 280hp is the cheapest I found from Summitracing.com)or go 2 a local shop and see if they have anything like a 355 or something. Theres a place here(AZ)that has turnkey 355s for somethin like 3k or so. Mods wont be much besides different motor mounts. But good luck on ur decision and finding everything u need. __________________ Ride Til I Die**

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10-10-2007, 07:18 AM	#2
tjzz4 Senior Member Join Date: Oct 2007 Posts: 276	Change the rear end gear ratio to a lower gear...

10-10-2007, 08:18 AM	#3
75K30 Senior Member Join Date: Jul 2006 Posts: 2,992	a 262 gas engine with 9:1 compression (pre votec) was making a little bit over 120 hrseower. Chasing bigger horsepower numbers are going to be unrealistic at best. Even if my numbers are conservative, you would have to find a "magic bullet' that could produce at least a 100% increase in power. Later model vortec's with better heads and roller cams and central port injection (W code vortec's) could make as much as 170-180 Hp. This is gonna require a bunch of modification. With that comes money. In this case the least expensive option would have been a lerger displacement engine. Changing the torque multiplier (converter) can be done, but is going to require compromise. This compromise is going to be a slightly higher stall speed. Higher stall speeds will equal more heat in the transmission, and more heat equals less transmission life. tjzz4 provided great advice, that is often overlooked. Changing the gear ratio in the axle will provide a guaranteed increase in performance, by creating a mechanical advantage.

10-11-2007, 06:08 AM	#5
Old Chevy Guy Junior Member Join Date: Oct 2007 Posts: 2	Guys, I appreciate all your suggestions and I think I already knew the answer in my mind. I made a mistake in putting the 4.3 motor in this truck. I could probably "doctor up" the motor and get a few more "hardly noticeable HP but, I would spend $500 to $1000 doing that and still would have a "weak engine" for a full size chevy truck. Would work great in an S10. I guess I was hoping for some magic. I can sell this 4.3 with less than 500 miles on it for $800-900 and put $1000 with it and drop in a 350 like I should have done at the beginning. The only questions I have is: 1. Will I have to change out the wiring harness? 2. Will I have to change out the ECM or just the prom? 3. Will I have to rework the emmission control & map sensors, etc? Thanks again for your help...