Stupid question

[gmcowner22]

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?

[Mr Diesel]

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.

[Shifty]

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)

[gmcowner22]

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.

[Shifty]

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.

[csdineley]

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.

[JohnnyPopper]

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.

[gmcowner22]

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).

[David Staines]

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.

[78 Chevyrado]

TBI all day.   starts every time.  no messing with the carb settings for seasonal changes.  couple more mpg.   There are resources today to tune them (make it work somehow) yourself a lot better than when I had my 87 R10. 

My 87 R10 came with a worn out 305/th700.    It ended up with a 73 caprice 400sb in it on TBI.   Back then...   I just filled the canted center bolt holes in the intake and bolted the intake to engine using the bolts at the front and back only.  worked and didn;t leak for 50k till i wrecked that truck.   I had 454 injectors in it, the computer out of a 350 police car tbi i found in the junkyard.  it ran great.   Fuel ratio guage I bought and put in it said it was doing the same as the 305 that was in it before the swap.   this was all back in 2004-2005.   didn't have a whole lot of internet help back then.

It's more versatile than people give it credit for.  and it always starts in all weather.

[78 Chevyrado]

Had this fuel ratio guage to make sure it was working right.

Engine pic shows the block number 3951511.  400SB.

Probably the only 400sb TBI anyones ever seen.   just had to use 454 injectors and a 350 tbi computer out of some year of caprice police car.  ( i dont remember what year the car was it just happened to be in the junkyard and had a 350 in it...)

[78 Chevyrado]

I went from a worn out 305 that would downshift into third on every mole hill to that 400 that could climb fairly steep grades and never unlock the TQ converter.  night and day difference.   

I'm just sayin, If I could make tha work you can make your work and keep it stock and it'll be a better truck.  fuel injection no matter how primitive is better on stock type vehicles. 

Pics are the 73 Caprice classic the engine came out of.  Grandad bought it new.  I now wish like heck I hadn'ta wasted it on that truck and woulda had it to put in my 78 C20 I have now which grandad bought new also...lol

Pushrod pic is an interesting one.  that was one of the pushrods out of the old 305.   look at the tip!   Thing still ran just fine!

[78 Chevyrado]

Me personally, never again with carbs.  I know how to work on them, I know how to tune them but I've been spoiled by these new cars and I don;t wanna be forced to tinker anymore.  If I feel like tinkering fine.  Forced tinkering is not fun.  I wanna drive it not tinker with it...  mostly...lol