TBI to Carburetor and back... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BurbanLife · 05-18-2015, 04:02 PM

Yesterday I purchased my long awaited project. A 1990 GMC Suburban 2wd. The engine was rebuilt recently and the original owner opted to remove the TBI and replace it with a carburetor. After carefully looking it seems as if the TBI itself was removed and a carburetor slapped in it's place. A couple manifold spacers in there and the carb doesn't seem to fit it correctly. Can I go back to the TBI or is it even worth it at this point. Oh yeah, the service engine light is on aswell. I'm guessing due to all the wiring and such still being there. Despite that hiccup the body is in phenominal shape minus a paint job.

68Timber · 05-18-2015, 05:55 PM

I'd convert it back to TBI. Think the PO might still have it?

BurbanLife · 05-18-2015, 06:54 PM

I just spoke with him. He has the throttle body but, not the manifold.

MalibuSSwagon · 05-18-2015, 10:10 PM

Should be easy to find a manifold. Or put an adapter on the carb intake.

BurbanLife · 05-20-2015, 02:37 PM

I am wanting to swap in a 454 eventually so do you think I should just wait until then? I'd have to swap the harness then anyway right?

68Timber · 05-20-2015, 04:58 PM

I'm not a TBI guru but I wouldn't expect the wiring to be different. You could probably find a manifold for cheap if not free, so if you're going back to TBI you may as well do it now and enjoy it on the 350 until you're ready for the 454 swap.

Hoods69BadBowTie · 06-07-2015, 07:10 PM

Yea that would make sense since I think a TBI fuel pump pushes at least twice as much fuel pressure as a carbed mechanical pump would. You can run a carbed motor with an electrical fuel pump just need a fuel pressure regulator. I would get a hold of the previous owner to find out more about that before you start tearing your hair out.

68Timber · 06-07-2015, 08:48 PM

He might have unplugged the original fuel pump and left it in the tank. Call him if you can, to save the trouble of dropping the tank to see. Also, the pump in the tank may be dead and part of the reason he put a carb on.

BurbanLife · 06-08-2015, 08:54 AM

I spoke to the original owner over the weekend. He said the intake manifold was swapped and TBI unit removed, distributor changed, and a mechanical fuel pump added. All the wiring and sensors were left intact as well as the in tank fuel pump. So I'm thinking at best I need a manifold, TBI unit, distributor, and fuel pump block off plate at the very least. This was all done 1,000 miles ago, when replacing the pistons and doing a valve job on the heads, so he says.

05-18-2015, 04:02 PM	#1
BurbanLife Registered User Join Date: May 2015 Location: Central Florida Posts: 11	TBI to Carburetor and back... Yesterday I purchased my long awaited project. A 1990 GMC Suburban 2wd. The engine was rebuilt recently and the original owner opted to remove the TBI and replace it with a carburetor. After carefully looking it seems as if the TBI itself was removed and a carburetor slapped in it's place. A couple manifold spacers in there and the carb doesn't seem to fit it correctly. Can I go back to the TBI or is it even worth it at this point. Oh yeah, the service engine light is on aswell. I'm guessing due to all the wiring and such still being there. Despite that hiccup the body is in phenominal shape minus a paint job. Attached Images __________________ 2005 Chevrolet Suburban Z71 4WD

05-18-2015, 05:55 PM	#2
68Timber I know the pieces fit Join Date: Nov 2007 Location: MONTGOMERY, AL Posts: 5,523	Re: TBI to Carburetor and back... I'd convert it back to TBI. Think the PO might still have it? __________________ John 79 2wd Blazer (Bruiser) 85 M1009 Blazer (Sarge) build 74 Honda Z50 build

05-18-2015, 06:54 PM	#3
BurbanLife Registered User Join Date: May 2015 Location: Central Florida Posts: 11	Re: TBI to Carburetor and back... I just spoke with him. He has the throttle body but, not the manifold. __________________ 2005 Chevrolet Suburban Z71 4WD

05-18-2015, 10:10 PM	#4
MalibuSSwagon Registered User Join Date: Sep 2009 Location: Weare,NH Posts: 1,590	Re: TBI to Carburetor and back... Should be easy to find a manifold. Or put an adapter on the carb intake. __________________ Eric 1992 Oldsmobile Custom Cruiser 1986 Chevrolet C10\|5.3L\|TKO600\|Shortbed\|Custom Deluxe 1983 Malibu Wagon\|TPI 305\|T5 5 speed\|3.73 non-posi

05-20-2015, 02:37 PM	#5
BurbanLife Registered User Join Date: May 2015 Location: Central Florida Posts: 11	Re: TBI to Carburetor and back... I am wanting to swap in a 454 eventually so do you think I should just wait until then? I'd have to swap the harness then anyway right? __________________ 2005 Chevrolet Suburban Z71 4WD Last edited by BurbanLife; 05-20-2015 at 02:47 PM.

05-20-2015, 04:58 PM	#6
68Timber I know the pieces fit Join Date: Nov 2007 Location: MONTGOMERY, AL Posts: 5,523	Re: TBI to Carburetor and back... I'm not a TBI guru but I wouldn't expect the wiring to be different. You could probably find a manifold for cheap if not free, so if you're going back to TBI you may as well do it now and enjoy it on the 350 until you're ready for the 454 swap. __________________ John 79 2wd Blazer (Bruiser) 85 M1009 Blazer (Sarge) build 74 Honda Z50 build

06-07-2015, 07:10 PM	#7
Hoods69BadBowTie Chevys Kick A$$ Join Date: Jan 2005 Location: Zootown, MT Posts: 12,699	Re: TBI to Carburetor and back... Yea that would make sense since I think a TBI fuel pump pushes at least twice as much fuel pressure as a carbed mechanical pump would. You can run a carbed motor with an electrical fuel pump just need a fuel pressure regulator. I would get a hold of the previous owner to find out more about that before you start tearing your hair out. __________________ HOODS is what I answer too -'79, '77, '88 Pickup Sold, '85 Camaro, '83 T/A, '81,'83,'90 K5 Blazer All Sold -'79 3/4 ton "Big Yellow Bananna" Lifted 4spd. 39.5 TSL Swampers, The money Pit -'86 K5 Blazer Silverado 6.2 4" lift 35"s -'95 Ext. Cab Shorty 4" Tuff Country rolling 35" M/T's -'83 Monte Carlo T-Tops. 126,500 Original Miles -LATER I would rather push a Chevy then drive a ford!!

06-07-2015, 08:48 PM	#8
68Timber I know the pieces fit Join Date: Nov 2007 Location: MONTGOMERY, AL Posts: 5,523	Re: TBI to Carburetor and back... He might have unplugged the original fuel pump and left it in the tank. Call him if you can, to save the trouble of dropping the tank to see. Also, the pump in the tank may be dead and part of the reason he put a carb on. __________________ John 79 2wd Blazer (Bruiser) 85 M1009 Blazer (Sarge) build 74 Honda Z50 build

06-08-2015, 08:54 AM	#9
BurbanLife Registered User Join Date: May 2015 Location: Central Florida Posts: 11	Re: TBI to Carburetor and back... I spoke to the original owner over the weekend. He said the intake manifold was swapped and TBI unit removed, distributor changed, and a mechanical fuel pump added. All the wiring and sensors were left intact as well as the in tank fuel pump. So I'm thinking at best I need a manifold, TBI unit, distributor, and fuel pump block off plate at the very least. This was all done 1,000 miles ago, when replacing the pistons and doing a valve job on the heads, so he says. __________________ 2005 Chevrolet Suburban Z71 4WD Last edited by BurbanLife; 06-08-2015 at 09:20 AM.



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