Throttle body V6 to V8 conversion question.......

cooke

Amateur Racer
Jan 9, 2005
261
0
0
Stanton, Texas
Today I picked up an extremely clean 87' Grand Prix with only 54K miles on it. It has the original throttle body 4.3 V-6 with a rod knocking. (Abusive grandson in Grandma's car). Anyway; what will it take to swap over an 88' - 95' throttle body V-8 into the car as far as ECM, wiring harness, etc. is concerned?
I realize nowadays everyone is going with the LS series motors for swaps; but I've owned three throttle body vehicles and all have given great service and went over 300,000 miles without a single bearing failure. Very reliable transportation. I'm wanting to have a driver with V-8 power, fuel injection; but not get into a complicated swap.
Any input would be greatly appreciated.
 

Deuce4935

Frequent Racer
Nov 19, 2007
341
0
0
Chicago, Il
cooke said:
Today I picked up an extremely clean 87' Grand Prix with only 54K miles on it. It has the original throttle body 4.3 V-6 with a rod knocking. (Abusive grandson in Grandma's car). Anyway; what will it take to swap over an 88' - 95' throttle body V-8 into the car as far as ECM, wiring harness, etc. is concerned?
I realize nowadays everyone is going with the LS series motors for swaps; but I've owned three throttle body vehicles and all have given great service and went over 300,000 miles without a single bearing failure. Very reliable transportation. I'm wanting to have a driver with V-8 power, fuel injection; but not get into a complicated swap.
Any input would be greatly appreciated.

The complete harness, computer and all related sensors. Since the GP is already injected all you have to do is install a bigger pump on your sender unit, and the stock fuel lines will connect right to the v-8 engine. The harness can be modified to eliminate all the unwanted and unused wires. Its not a hard thing to do if you can get gm shop repair manuals for both vehicles. Good luck with it and post pics. While you're at it, go ahead and find a 8.5 from a 442 or Grand National because you will develop some traction issues.
 

cooke

Amateur Racer
Thread starter
Jan 9, 2005
261
0
0
Stanton, Texas
The complete harness, computer and all related sensors. Since the GP is already injected all you have to do is install a bigger pump on your sender unit, and the stock fuel lines will connect right to the v-8 engine

Are you saying that I'll need all that stuff or just the bigger pump? I was wondering if the computer out of an 87 EFI truck with a manual trans would work? On these models are the transmissions involved at all? The reason I bring up the trans deal is because the car has the weaker "200" or whatever they were. It does not have an overdrive.
Thanks for taking the time to reply.
 

Deuce4935

Frequent Racer
Nov 19, 2007
341
0
0
Chicago, Il
cooke said:
The complete harness, computer and all related sensors. Since the GP is already injected all you have to do is install a bigger pump on your sender unit, and the stock fuel lines will connect right to the v-8 engine

Are you saying that I'll need all that stuff or just the bigger pump? I was wondering if the computer out of an 87 EFI truck with a manual trans would work? On these models are the transmissions involved at all? The reason I bring up the trans deal is because the car has the weaker "200" or whatever they were. It does not have an overdrive.
Thanks for taking the time to reply.

You will need all the things above and the bigger pump. Also if the trans is a manual then the computer does not control its shifts, but you will need the to control the the engines functions. Also, if the trans is a 200c then its shifts are controlled by the linkage on the throttle body but that particular trans is going to get murdered by the engine. Look for a 350, 400, (200-4r, or 700r4 trans that can handle the power and has the overdrive).
 

87SS-ZZ3

Frequent Racer
Oct 9, 2004
385
0
0
Pantego, NC
I just read thru the post. Swaping to the v8 from the 4.3 is super easy. I have done this and all you need is the v8 distributor and of course the v8 with proper manifolds. Every sensor, the harness and computer will work fine. The throttle body is a little small, but will work fine for a stock engine. I HAVE done this with S10 engine swaps to V8. Swap the trans to a 2004R and you've got a great driver.
 

cooke

Amateur Racer
Thread starter
Jan 9, 2005
261
0
0
Stanton, Texas
87SS-ZZ3 said:
I just read thru the post. Swaping to the v8 from the 4.3 is super easy. I have done this and all you need is the v8 distributor and of course the v8 with proper manifolds. Every sensor, the harness and computer will work fine. The throttle body is a little small, but will work fine for a stock engine. I HAVE done this with S10 engine swaps to V8. Swap the trans to a 2004R and you've got a great driver.

Thanks! I was hoping for an easy swap. The GP already has the tank mounted fuel pump, etc. Nothing has ever been touched on this car.
What if I use the throttle body off of a 5.7 truck? That should take care of the "lean" condition, shouldn't it? Again; thanks for the reply.
 

Deuce4935

Frequent Racer
Nov 19, 2007
341
0
0
Chicago, Il
cooke said:
87SS-ZZ3 said:
I just read thru the post. Swaping to the v8 from the 4.3 is super easy. I have done this and all you need is the v8 distributor and of course the v8 with proper manifolds. Every sensor, the harness and computer will work fine. The throttle body is a little small, but will work fine for a stock engine. I HAVE done this with S10 engine swaps to V8. Swap the trans to a 2004R and you've got a great driver.

Thanks! I was hoping for an easy swap. The GP already has the tank mounted fuel pump, etc. Nothing has ever been touched on this car.
What if I use the throttle body off of a 5.7 truck? That should take care of the "lean" condition, shouldn't it? Again; thanks for the reply.

You want to use the entire v-8 setup, that MEANS EVERYTHING that came on the v-8 engine from intake to the oil pan. If you put a v-6 tb on a v-8 engine of course its going to run lean, if it were that simple without repercussions then the factory would have loved saving money and going that route. Save yourself the time, energy, money and frustration and do it right the first time.
 

87SS-ZZ3

Frequent Racer
Oct 9, 2004
385
0
0
Pantego, NC
If you have the complete v8, by all means use the v8 stuff. If you don't have it use the v6 stuff. I know what works for me.
 

cooke

Amateur Racer
Thread starter
Jan 9, 2005
261
0
0
Stanton, Texas
QUOTE: You want to use the entire v-8 setup, that MEANS EVERYTHING that came on the v-8 engine from intake to the oil pan. If you put a v-6 tb on a v-8 engine of course its going to run lean, if it were that simple without repercussions then the factory would have loved saving money and going that route. Save yourself the time, energy, money and frustration and do it right the first time

Agreed; but why would I need the entire wiring harness; if the car is already TBI equipped? I do have access to a complete TB V-8. And I could see where I would need the V-8 ECM to control pulses to the Throttle body.. Anyway; I'm not arguing with anyone; I'm the one who came on here asking for help. I know the easiest thing to do would be to put my Holley on and a MSD distributor and forget it. But I'm looking for something that is very reliable and has good idle quality ( just opposite of what I've been doing since I was 17) This isn't going to be a street/strip 11 second ride. I've got that.
Anyway; on the ECM; will any 87' - 95' V-8 TB work to fill the bill or is there specifics that I need to be looking for?
As far as rear-ends go; I've got 8.5's and the transmissions aren't really an issue either. I've got access to those as well.
I appreciate both of you guy's input; Im just trying to get a game plan going here where I can gather up everything to get it up and running right.
 

87SS-ZZ3

Frequent Racer
Oct 9, 2004
385
0
0
Pantego, NC
I would use the factory ecm in the GP. TBI is very forgiving. Back in the 80's even the proms listed 4.3 - 7.4, for the same prom. I've been in a GM dealership for almost 20 years as a service tech. Like I said before, I know what works for me. I would suggest an adjustable fuel regulator, or dilling out the brass and making the stock (one adjustable) HTH
 

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