TBI Swap....

[CaliDude76]

Just got my truck smogged today, took him a lil bit to adjust the carb and stuff to get it to pass...

he was telling me that if i wanted, or could do it.. is put a throttle body on my square...
stock it has a 350 with that lovely Q-Jet M4ME style hooked up to a emmisions system (pump, egr valve, ECU, Check Engine Light, O2 Sensor, and a rat's nest of vacuum hoses).. since I have to have that here in Cali to register...

Dude said I could legally swap all that vacuum junk and carb to a TBI set-up from like a 87 or newer... has any of you fellas done this swap, with the harnesses, intake and such?? I consider myself a pretty good shade-tree dude,

curious to know the difficulty level of all this.... I'm sure it would make my stay more at a consistent idle level.. since my carb fluctuates too much..(somedays shes smooth as silk, and other days... a twitchy son of a gun) I have a vacuum leak somewhere.. and it's gonna take a miracle for me to find that sucker....

 

[RetroC10Sport]

You could go all out and go TPI.

Wiring will be the most difficult, but if you get the entire harness, it should be cake. I doubt you'll even have to change the throttle cables or anything like that.

Intake, TBI, air cleaner, ECM, harness is what i can think of that you need.

 

[Irishman999]

It seems like the fuel lines would be a pain in the ass since you have to switch over to high pressure.

My uncle did it to his 87, he said he basically went to the parts yard and pulled a later model intake, throttle body and associated electronics, bolted it to his 350 and found an aftermarket wiring harness.

I keep thinking about that idea too, I have really bad luck with carbs.

 

[Swims350]

distributor and heads. porbably won't need the air cleaner the old one may work.

I don't think your truck has an o2 sensors not that I could think of, but look in you rmanifold or exhaust pipe and see, if not you need one for the tbi setup. The 88 and newer should work as well, problem is the heads are different. The only real difference is the four center bolt holes on a different angle. You could maybe drill them out and make them work with your heads, and you could also get an adapter plate and make the tbi fit the intake you have, just change the dist, but you also need a coolant temp sensor, not sure if there's a spot to plumb that into or if you could use the head location to do so. You need the coil as well as it mounts on the intake if you upgrade the dist. I saw another guy do tbi on his old truck on 67-72 and I don't think he changed alot of things, but looked like he did a ton of wiring. The reason for that was him not putting in the dist and such I guess.

The fuel system is a problem the tbi trucks had in tank pump, and I know my 88 newer body style truck has braided lines, and they come up the driver's side of the frame. TBI only uses around 13-15 psi though.

 

[RetroC10Sport]

ooh yeah, distributor and fuel pump, but you could get away with running an aftermarket electric pump.

 

[Old77]

I can see another write up in GMSB's future

 

[Swims350]

good point retro man forgot about the in line frame rail ones. You sure could. Then use a pressure regulator to be sure.

Although if you are going to the junkyard or parts truck for the harness and intake and stuff might as well try to get at least the fuel tank sending unit. Bad thing is on the squares only year was 87. Then it'd have to be a long or short bed whichever yours is to be the same size tank. Drop it and put it in all that crap, so it would be up to you, junkyard and buy a new pump to be sure, or buy the aftermarket one and a reg.

I hope it's ok to post links from a competitors site, if not guys delete the links for me or let me know....

http://67-72chevytrucks.com/vboard/showthread.php?t=442854
http://67-72chevytrucks.com/vboard/showthread.php?t=317519

 

[CaliDude76]

Hmmm.. interesting fellas... didn't think about having to change out the distributor, or fuel pump... seeings that my 84 has the mechanical one up along the side. So there's no way it would work with a manual fuel pump?.. and why the distributor change? I'm a curious fellow about these things....I can understand the wiring, and using the ECU to control the TB itself..

..so, I could just keep my same intake set-up too?... an intake off of a newer truck... lets say.. 87-91 350 TBI Burb..Blazer.. or Crew Cab wouldn't just bolt directly on the 350 I have now?

My square has a G.M. Goodwrench Crate 350 with about 20,000 on it

 

[RetroC10Sport]

Hmmm.. interesting fellas... didn't think about having to change out the distributor, or fuel pump... seeings that my 84 has the mechanical one up along the side. So there's no way it would work with a manual fuel pump?.. and why the distributor change? I'm a curious fellow about these things....

also... I could just keep my same intake set-up too?... an intake off of a newer truck... lets say.. 87-91 350 TBI Burb..Blazer.. or Crew Cab wouldn't just bolt directly on the 350 I have now?

My square has a G.M. Goodwrench Crate 350 with about 20,000 on it

The TBI distributor uses pulses that also fire the injectors.

 

[CaliDude76]

distributor and heads. porbably won't need the air cleaner the old one may work.

I don't think your truck has an o2 sensors not that I could think of, but look in you rmanifold or exhaust pipe and see, if not you need one for the tbi setup.

Yeah.. it does have a O2 sensor.. had to replace it a few days ago...

I read this right up after typing my last post.. so I suppose I could use a TBI with my intake... they have adaptors huh?

 

[Swims350]

the manual fuel pumps only put out 4-7 psi if that and you need 12-15 psi 12 at least but not really more then 15.

The four center botl holes are at a different angle, you may be able to re use yours but you need a spot for the coolant temp sensor. Not sure how that works out.

The other intakes are the sam way if you got a tbi intake you would need to make the holes bigger in the center to bolt to your heads. Also alot of them have a rear water crossover, and your heads may not have them not sure. I know my 88 the heater hose is in the intake in back.

You are not limited to the burb and blazers, the 88-95 or so trucks and blazers and stuff had tbi. You could use that setup too.

 

[RetroC10Sport]

1988-92 Camaro/Firebirds had a 305 TBI option that would work, as did the big cars.

 

[HotRodPC]

Noway it will work with a manual pump. Manual pump or carb is good for about 5-7PSI. TBI needs like 14-17lbs PSI, and SFI or MultiPort Injection needs 20-25PSI. Those are guestimations on the pressures, so if I'm off a couple lbs, that is why. I didn't look it up, just going off old memory.

Really, its not gonna be that hard to do. And being in CA, I'd say its a worthwhile ordeal. Also likley a bit better mpg, much easier cold starts which isn't usually a problem anyway in CA, but the TBI system is very dependable too once you get it all done and set up right. You could just about weld the hood closed if you did it.

 

[HotRodPC]

Awww, sorry Swims. I was skimming. Didn't see your pressures post. I guess mine did come close to yours anyway. Must mean we both know what we are talking about.

 

[Swims350]

lol it's ok man good to have a second opinion. You would be correct at being very close, you can get by with around 12 psi bu that's on the low side and you really need like 12.5-14 or so. I think 13 is ideal, but you could see around 15.

Also forgot on my other post, you shouldn't need a pressure regulator, the tbi has one built in. it's good to check the spring in them because they can break and cause bad pressure, and issues, and you can make it adjustable or buy the ones that are and put in it's place.