Gain extra benefits by becoming a Supporting Member Click here find out how!
Classic Performance Products Classic Parts
Ciadella InteriorsAmerican Auto Wire Classic Industries
Chevs of the 40sDanchuk Catalog
Hellwig Products IncPerformance Rod & CustomEcklers AutoMotive
Nu-Relics Power Windows
Impala Bob's Bob's Chevy Trucks Bob's Chevelle Parts Bob's Classic Chevy

Username Post: Anyone still doing tbi to carb swaps?        (Topic#346529)
SBCguy 
Forum Newbie
Posts: 14

Loc: Youngstown, OH
Reg: 07-30-14
08-11-17 03:49 PM - Post#2703800    

So after quite a few years of an ongoing issue with my truck, I think I will be replacing the computer controlled junk with a carburetor and be done with it. I've got a 1988 c3500 2wd with a 350 and muncie sm465.
So long story short, when I bought the truck off the PO, this thing wouldn't stay idling without giving it some throttle. I tried to make it right but after replacing many parts, I decided to unplug the map sensor, making it run rich, and advance the timing just to make it driveable. I parked the beast last year due to some issues, but winter is not too far ahead and will be needing a winter ride.
I was just curious if someone out there has done something like this before and could recommend what I will need for this swap. I am aware of the oddball angles on acouple of the intake bolts. Saw on Summits website a weiend carbureted intake manifold for the tbi heads. Was also thinking about just using the stock pump and installing a return style inline regulator. Any advice on this subject? Thanks in advance.



 
Low priced Genuine GM Auto Parts
bowtie44s 
Valued Contributor
Posts: 3738
bowtie44s
Age: 34
Loc: wv
Reg: 08-29-12
08-11-17 08:24 PM - Post#2703827    
    In response to SBCguy

It is a pretty easy swap, but first let me try to discourage you. The stock TBI works great for a stock engine. If you double the horse power, I will agree 110%, the stock TBI will not keep up. You can easily fix the problem for way less than what you will have in the carburetor. If you are absolutely sure this is what you want to do, I will tell you in detail how.


Jeff

'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap


 
2plus2 
Member
Posts: 1070

Loc: Langley,BC
Reg: 02-03-05
08-11-17 08:46 PM - Post#2703833    
    In response to bowtie44s

By the time you buy all the parts needed for the swap you can replace every sensor and keep the tbi not to mention you want this as a winter truck you will hate dealing with a carb in the winter
Plug your map back in
Replace the coolant sensor in the intake with a good ac delco one
Test your IAC
And look at the throttle body shaft to see if its
Worn
Tbi is a very easy system to work on and fairly cheap to fix when it fails

69 Canadian Pontiac 2+2
factory L48 350 Chev,TH350,PW,PT
99 Silverado RCLB 4.8 NV4500 14BSF 4.10's locker 6" Procomp 35 bfg m/t's 9k winch cutout flares
07 Town Car Loaded,Tinted,Getting Bagged


Edited by 2plus2 on 08-11-17 08:47 PM. Reason for edit: No reason given.

 
SBCguy 
Forum Newbie
Posts: 14

Loc: Youngstown, OH
Reg: 07-30-14
08-12-17 01:39 AM - Post#2703836    
    In response to bowtie44s

I appreciate you guys trying to discourage me but I've been tinkering with the truck since I bought it in late 2013. The amount of time and money I have in it, I should have done this swap to begin with. Yes I am 100% absolutely sure this is what I want to do. The reason I parked the beast last year was, the idle valve was stuck closed one cold morning. Had an extra one so I figure change it right there. With only a quarter of a turn, broke off in the throttle body. Buddy gave me a good used throttle body and I bought a new IAC. Still wouldn't run properly. Replacing parts left and right to get it right but after putting quite a bit into it I gave up again, and let it sit until I have the time to do this swap.

1980 El Camino 283 transplant
(Will be running by spring '17)
'88 C3500 350 muncie 465 4:10 rear end
Will pull a house down!


 
bowtie44s 
Valued Contributor
Posts: 3738
bowtie44s
Age: 34
Loc: wv
Reg: 08-29-12
08-12-17 08:41 AM - Post#2703868    
    In response to SBCguy

  • SBCguy Said:
Yes I am 100% absolutely sure this is what I want to do.



In addition to a carburetor, you will need a coil-in-cap vacuum advance HEI distributor and a return style fuel regulator. Your best bet will be to run 3/8 hose from the tank to the regulator and back to the tank. Regulate the fuel pressure to 4-5psi and hook it to the carb.

You will need a keyed hot going to the distributor. I ran mine off of a relay with 10 gauge wire. I found a keyed hot in the convenience center behind the parking brake pedal and ran 16ga to the 86 pin on the relay. You HAVE to get one that is hot in the crank position. There is only one or two. That I could find. Once this is done, it will start once the float bowls are full, but the fuel pump will shut off in 3 seconds and it will die. To fix this, cut the purple wire that went to the old distributor and run it to the tach feed on the coil. The pump will prime for 3 seconds and quit then run continuous once it's started.

You'll have around $600 in it if you buy a $300 carburetor. Don't mess with anything other than a Quick Fuel or Holley.

Jeff

'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap


 
SBCguy 
Forum Newbie
Posts: 14

Loc: Youngstown, OH
Reg: 07-30-14
08-12-17 12:43 PM - Post#2703889    
    In response to bowtie44s

Thanks, alot actually. That was the kind of information I was looking for. I have a few carbs lying around but they would be either too big or too small for this swap. Thinking maybe find and rebuild a used holley 650.
I wont be taking on this project right away due to some current events (middle of buying a house) but I would like to keep you guys updated. Thanks again

1980 El Camino 283 transplant
(Will be running by spring '17)
'88 C3500 350 muncie 465 4:10 rear end
Will pull a house down!


 
bowtie44s 
Valued Contributor
Posts: 3738
bowtie44s
Age: 34
Loc: wv
Reg: 08-29-12
08-12-17 02:39 PM - Post#2703899    
    In response to SBCguy

One more thing, your service engine light will be on forever. I can't stand stuff like that. You can open the cluster and pull the bulb. It's especially easy on yours since it should have a moony cluster.

Jeff

'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap


 
SBCguy 
Forum Newbie
Posts: 14

Loc: Youngstown, OH
Reg: 07-30-14
08-12-17 05:23 PM - Post#2703928    
    In response to bowtie44s

That doesnt really bother me, especially that truck. As long as it runs I'm fine with it. Put a piece of electrical tape over it, "there, I fixed it." Lol

1980 El Camino 283 transplant
(Will be running by spring '17)
'88 C3500 350 muncie 465 4:10 rear end
Will pull a house down!


 
Low priced Genuine GM Auto Parts
Icon Legend Permissions Topic Options
Report Post

Quote Post

Quick Reply

Print Topic

Email Topic

586 Views
FusionBB
FusionBB™ Version 2.1
©2003-2006 InteractivePHP, Inc.
Execution time: 0.276 seconds.   Total Queries: 17   Zlib Compression is on.
All times are (GMT -0800) Pacific. Current time is 08:03 PM
Top