88 4.3 - 350 swap questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

406 C-10 · 03-12-2003, 08:00 PM

My daily driver 88 1/2 ton cheyenne right now is limping along on a weak high mile 4.3 liter 6cyl. I am planning on putting a 350 between the fenders like there should be and i wanna know what all its gonna take. I know motor mounts bigger radiator and fuel pressure regulator because im ditching the TBI for a carb, is there anything else? And on the note it has a 3 speed auto with the METRIC stamped in the tranny pan will a th350 fit in its spot or will i need a new drive shaft?

**bwood** · 03-12-2003, 08:22 PM

If it were me, I would try and go back with the TBI. All you would need is an 88 350 TBI complete truck (I know, it sounds good if you say it fast) and you could swap components over (radiator, computer/ harness, motor mounts, accessory brackets, etc.). Even if the motor was high mileage, it sounds like you might already have a motor, important items like the intake, heads, and other TBI items would change over. When it came to the actual TBI, Holley makes a good high performance factory replacement unit that plugs into factory harness. I would stick with the existing tranny. If it is original, it would be a 700R4 (computer controlled 3 speed w/ overdrive). If you do decide to ditch the TBI for carburation, the computer will be worthless and so will be anything controlled by it (guages, 700R4 tranny, distributor/ timing, possibly the rear wheel ABS, etc.). Good luck, I hope some of this helps.

406 C-10 · 03-13-2003, 12:50 AM

i dont have the engine for the swap yet im looking right now dont have the cash but i will soon enough i just wanna plan ahead. It is not the 700r4 tranny its 3 speed without the overdrive. I would prefer to change over to a carb because i dont want to mess with the computer and all of that junk. The emissions regulations arent a big deal here (in Nebraska) they look under the vehicle for a cat and thats all, if you get pulled over. I also dont care about ditching the computer because the truck doesnt have ABS at all or an electronic advance dist. the computer is pretty much strictly fuel delivery so I dont feel it would be much of a loss.

69c10stepside · 03-13-2003, 03:50 PM

If you switch to carb on your truck, you do not lose out on your gauges for sure.. I have had my '89 gmc with out fuel injection for three years and everything that worked on my truck other then the tbi still works. As far as a fuel pressure regulator, I cant remember which one i got from summit, but it was around $35 something for it. I had a 90 model full size 4.3 liter truck, have you ever noticed that the motor mounts have a plate that moves the mount back? Take that plate out, pull the motor mounts off, and then put those mounts where that plate used to go. If your truck has a/c, it already has the "heavy duty" radiator that gm used in 4.3's with a/c and 305's and 350s. Your best bet on the switch over for the tranny is to measure the length of the transmission and from there one of us could tell you the overall length of a turbo350 short shaft long shaft etc. If you do switch out the transmission that you have in it now, and the one you put in does not have electric speedo on it, you will lose that. If you are interested, i have a late model style turbo 400 that has the electronic style speedo. It came out of a 90 model h/d 3/4 two wheel drive pickup, has around 45,000 miles.. it might need a tail shaft bearing, but that isnt much. If you have any more questions or anything else, pm me. Frank

stateamind · 03-20-2003, 02:29 AM

Better fuel mileage. Use the throttle body you have, just need to change injectors. Wiring harness is same. All front brackets are the same. Swap computer, engine mounts, fan shroud, radiator and get a set of shorty headers from Summit, $150 I believe. They will bolt to your stock y-pipe. 4.3 is just a 350 minus two cylinders. This is an easy swap to do. Just keep the TBI and computer. You'll be glad you did.
Hope this helps,
Mike

03-12-2003, 08:00 PM	#1
406 C-10 Registered User Join Date: Feb 2003 Location: Lincoln NE Posts: 20	88 4.3 - 350 swap questions My daily driver 88 1/2 ton cheyenne right now is limping along on a weak high mile 4.3 liter 6cyl. I am planning on putting a 350 between the fenders like there should be and i wanna know what all its gonna take. I know motor mounts bigger radiator and fuel pressure regulator because im ditching the TBI for a carb, is there anything else? And on the note it has a 3 speed auto with the METRIC stamped in the tranny pan will a th350 fit in its spot or will i need a new drive shaft? __________________ 69 C-10, 406 small block, double hump heads, performer intake, 750 holley, headers, dual 2 1/2 exhaust through glasspacks, yet to move 88 cheyenne tbi 4.3 daily driver

03-12-2003, 08:22 PM	#2
bwood Registered User Join Date: Jan 2003 Location: Denison, Texas Posts: 1,920	If it were me, I would try and go back with the TBI. All you would need is an 88 350 TBI complete truck (I know, it sounds good if you say it fast) and you could swap components over (radiator, computer/ harness, motor mounts, accessory brackets, etc.). Even if the motor was high mileage, it sounds like you might already have a motor, important items like the intake, heads, and other TBI items would change over. When it came to the actual TBI, Holley makes a good high performance factory replacement unit that plugs into factory harness. I would stick with the existing tranny. If it is original, it would be a 700R4 (computer controlled 3 speed w/ overdrive). If you do decide to ditch the TBI for carburation, the computer will be worthless and so will be anything controlled by it (guages, 700R4 tranny, distributor/ timing, possibly the rear wheel ABS, etc.). Good luck, I hope some of this helps. __________________ 2013 Ford F150 FX4 2006 Chevy Silverado 1500 1982 Chevy C1500 2020 Ford Explorer Limited 2008 Ford Escape Last edited by bwood; 03-12-2003 at 08:25 PM.

03-13-2003, 12:50 AM	#3
406 C-10 Registered User Join Date: Feb 2003 Location: Lincoln NE Posts: 20	i dont have the engine for the swap yet im looking right now dont have the cash but i will soon enough i just wanna plan ahead. It is not the 700r4 tranny its 3 speed without the overdrive. I would prefer to change over to a carb because i dont want to mess with the computer and all of that junk. The emissions regulations arent a big deal here (in Nebraska) they look under the vehicle for a cat and thats all, if you get pulled over. I also dont care about ditching the computer because the truck doesnt have ABS at all or an electronic advance dist. the computer is pretty much strictly fuel delivery so I dont feel it would be much of a loss. __________________ 69 C-10, 406 small block, double hump heads, performer intake, 750 holley, headers, dual 2 1/2 exhaust through glasspacks, yet to move 88 cheyenne tbi 4.3 daily driver

03-13-2003, 03:50 PM	#4
69c10stepside Large Member Join Date: Jun 2002 Location: Northwest Arkansas Posts: 747	If you switch to carb on your truck, you do not lose out on your gauges for sure.. I have had my '89 gmc with out fuel injection for three years and everything that worked on my truck other then the tbi still works. As far as a fuel pressure regulator, I cant remember which one i got from summit, but it was around $35 something for it. I had a 90 model full size 4.3 liter truck, have you ever noticed that the motor mounts have a plate that moves the mount back? Take that plate out, pull the motor mounts off, and then put those mounts where that plate used to go. If your truck has a/c, it already has the "heavy duty" radiator that gm used in 4.3's with a/c and 305's and 350s. Your best bet on the switch over for the tranny is to measure the length of the transmission and from there one of us could tell you the overall length of a turbo350 short shaft long shaft etc. If you do switch out the transmission that you have in it now, and the one you put in does not have electric speedo on it, you will lose that. If you are interested, i have a late model style turbo 400 that has the electronic style speedo. It came out of a 90 model h/d 3/4 two wheel drive pickup, has around 45,000 miles.. it might need a tail shaft bearing, but that isnt much. If you have any more questions or anything else, pm me. Frank __________________ 1989 GMC C1500 ECSB 1972 Gmc Jimmy 1972 Chevy C10 SWB Sold

03-20-2003, 02:29 AM	#5
stateamind And you call that a what? Join Date: Oct 2002 Location: Dickson, TN Posts: 171	Keep the TBI Better fuel mileage. Use the throttle body you have, just need to change injectors. Wiring harness is same. All front brackets are the same. Swap computer, engine mounts, fan shroud, radiator and get a set of shorty headers from Summit, $150 I believe. They will bolt to your stock y-pipe. 4.3 is just a 350 minus two cylinders. This is an easy swap to do. Just keep the TBI and computer. You'll be glad you did. Hope this helps, Mike



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