Author Topic: Stupid question  (Read 569 times)

Offline gmcowner22

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Stupid question
« on: April 07, 2023, 07:11:28 PM »
I have an 87 GMC Sierra Classic V1500 4x4, it has the TBI 350 in it and Im just wondering (not gonna do it just a thought that crossed my mind). Can I convert it back to a carburetor/HEI set up and completely bypass the computer? I know Id probably need a fuel pressure regulator to bring the fuel down from the 12 psi the TBI system uses to around 5.5 to 7 PSI for a carb. Could this be done or would I be better off saving up for a Holley SNIPER or equivalent self learning EFI setup?
"When you were born, you cried and the world rejoiced.
Live your life so that when you die, the world cries and you rejoice."
                                                [Cherokee saying]

1987 GMC V1500 Sierra Classic "Patch"

Online Mr Diesel

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Re: Stupid question
« Reply #1 on: April 07, 2023, 07:58:37 PM »
You would be best off just maintaining that TBI system you already have. GM TBI is a pretty good system, but like anything it needs maintenance and repairs from time to time.
1976 C20 Crewcab, 6.2L/SM465
1982 K30 Crewcab , 427TD/TH400
1983 C30, 6.2L/TH400
1983 K30 Crewcab 454/700R4
1986 K10 350/400. 1989 K30 cab/chassis 454/SM465

Offline Shifty

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Re: Stupid question
« Reply #2 on: April 08, 2023, 11:30:59 AM »
If your engine is stock, or stock-ish, the TBI will fine.  If you plan to make big horsepower, the TBI is really limited.  You can trick it out with a bunch of mods, but it probably wont support very much power. 

(I have the same set-up, though mine is the Chevy version-V20)
87 V20 Standard Cab Longbed (current)

87 R30 3+3 Longbed (days of yore)

98 C2500 ext cab longbed

Offline gmcowner22

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Re: Stupid question
« Reply #3 on: April 08, 2023, 03:20:15 PM »
I kinda figured as much, was mainly just one of those dumb ideas running around in my brain I thought I better get some feed back on. I will say the truck has better throttle response than my old carbureted 1980 but its gonna take some getting use to the pedal as its a bit touchy (ok more than abit) and it takes abit to get it started. Thinking I may pull the old unit off (PO said it had 164000 miles on the truck to begin with) so it may be time for a rebuild. Rock Auto has the kit with all the O-rings , gaskets etc. that id need but there's a few other things I need to address before I get to that. OH btw are TBI spacers worth the money or not? I dont think a TBI is as vulnerable to heat soak as a carb but this is my first TBI engine so Im not sure.
"When you were born, you cried and the world rejoiced.
Live your life so that when you die, the world cries and you rejoice."
                                                [Cherokee saying]

1987 GMC V1500 Sierra Classic "Patch"

Offline Shifty

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Re: Stupid question
« Reply #4 on: April 08, 2023, 06:33:04 PM »
A spacer isn't going to hurt anything, but your linkage may be a bit funky.  It seems like TBI units suffer from "drain-back" to the tank, and I've seen some folks do a  anti-drainback (one way valve).  Mine doesn't like to re-start when hot, and does take a little bit first start as well,  but I've learned to live with it.
87 V20 Standard Cab Longbed (current)

87 R30 3+3 Longbed (days of yore)

98 C2500 ext cab longbed

Offline csdineley

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Re: Stupid question
« Reply #5 on: April 08, 2023, 07:13:49 PM »
I did it. It was pretty easy. Yes you will need a fuel pressure regulator a HEI a Carb and an Intake. While I can't speak of the "Holley SNIPER or equivalent self learning EFI setup". I did mine back in 2013 and I haven't had to touch it since. I tried to keep the tbi going. But it kept giving me random problems every so often. I haven't noticed any difference in mpg.
1987 V20 Custom Deluxe, Vortec Headed 350, SM465,Np205 14Bff 4.10

Offline JohnnyPopper

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Re: Stupid question
« Reply #6 on: April 10, 2023, 12:00:45 PM »
From my recent TBI adventures, hard starting may be due to slow flow of fuel. I'd check the fuel filter, then pressure, or both while your at it.

Pretty sure the rubber line from the pump to steel feed line is broken/ruptured. I hear gas recirculating in the tank.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline gmcowner22

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Re: Stupid question
« Reply #7 on: April 11, 2023, 07:59:12 AM »
Ill check the filter I have a new fuel filter so I can change that out, as for pressure I dont have a pressure gauge but Im sure I could round one up. It does seem to start ok once its warm, Im just hoping its nothing major at this point other than maybe a new filter and a new cap an rotor (got that too just havent gotten it on yet).
"When you were born, you cried and the world rejoiced.
Live your life so that when you die, the world cries and you rejoice."
                                                [Cherokee saying]

1987 GMC V1500 Sierra Classic "Patch"

Offline David Staines

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Re: Stupid question
« Reply #8 on: June 07, 2023, 09:31:46 PM »
When I bought my '85, it had gone through an itteration of 2nd level troubleshooting. It had a TBI system on it (not the place to argue 85 with TBI) and had just had the 305 replaced with a newly rebuilt 350. The person who owned it was a mechanic and fought with it for some time thinking there was a TBI problem. Finally, they just took the TBI off and installed a regulator and 1406. This did not solve the problem which eventually turned out to be a flat lobe on the cam. I bought the truck with the 1406 and a new Cam. When I bought the truck, I insisted they include a holly sniper that they had at the shop.

Last month, I started the sniper installation process. You'll need new fuel pumps. You might need a new engine side bay harness (or be able to rework the existing one). If you have switchable tanks, you'll need to weigh that when it comes to how you're going to get 65 psi on the fuel line to the sniper (sniper has a built in regulator). Fortunately, you already have a return line. If it's a single tank, it's relatively easy but will require more than just the carb. I had dual tanks so my solution was a bit more complicated.