TBI to Carb

[Mkuhn138]

I got a great deal on a GMPP ZZ4 fast burn engine that is being fully blueprinted. It was my brother's back up engine for his super late model car. We know it will produce about 475hp with a better cam, slightly different internals, machine work, and good carb. I'm going to be dropping it in, in place of my 350 TBI. Has anybody else made this switch, and if so what were the issues you ran into?

I know that TBI is typically considered better than carb, but in this application I don't think it will give me what I need - so please don't respond that I'm going backwards.

Thanks,

Matt

 

[shadowwalker_02]

I just did this in my project. Basically all you need is a 12v hot wire to the dizzy while the key is on. Either install a fuel pressure regulator and keep the tbi sending unit or swap to a plain carb'd 3 outlet sending unit and put a mechanical pump on the motor ( I went with the mechanical pump and new carb'd sending unit).

Other than the fuel lines (depending on which sending unit you use) I can't really think of anything else. It's pretty simple I think once you plan it all out.

Here is what I did http://coloradok5.com/forums/showthread.php?t=274978&page=6

Hope this helps.

 

[Mkuhn138]

It looks like you left the computer in place - Did you just coil up the wiring behind the dash? Also, did you just disconnect the electric fuel pump and leave it in the tank, or did you pull it all together?

Thanks,

Matt

 

[shadowwalker_02]

I pretty much left everything in place. The computer I left in the same position and just zip tied everything to make it look decent. I coiled all the engine bay TBI wires and zip tied them to the firewall on the pass side above the stock heater location. In case for whatever reason I would want to go back to TBI plus I didn't really want to hack the wiring up. May look cluttered but at least nothing will ground out electrically.

I pulled the tbi sending unit out and swapped in a 3 outlet one to run. I was going to run the pressure regulator but I wanted to keep it simple and mostly hassle free.

 

[Wyomingboy]

I just pulled my TBI off also, but I went to a FAST stand alone fuel injection system. But the procedure is almost the same.

With mine I used an adjustable fuel pressure regulator on the firewall to get the fuel pressure I wanted. I did have to wire in my own fuel pressure relay and run a wire back to the supply side of the existing fuel pump. That way my gauge still works , but I have an independent power source(not controlled by the computer) wired to a hot with key on source to run the fuel pump.

2nd you leave the computer in place, that way your other gauges will work and a biggy, your speedometer !

I cut off my excess TBI sensor wires on the harness and taped up the cut areas to keep out contamination. The computer just thinks they are disconnected. I do have a "check engine" light and I am going to take it out.
Also you will have to rig up a Torque converter lockout switch to activate your lock up now, as that was controlled by the computer before. But it's not a big deal, just Google it and you'll find several options. Basically you just have to supply power with a toggle switch to the transmission pin that was powered before, by the computer and then you switch it manually, whenever you are on the highway.

That's about it, use a manual distributor & set your timing manually.

Good Luck

 

[shadowwalker_02]

Also you will have to rig up a Torque converter lockout switch to activate your lock up now, as that was controlled by the computer before. But it's not a big deal, just Google it and you'll find several options. Basically you just have to supply power with a toggle switch to the transmission pin that was powered before, by the computer and then you switch it manually, whenever you are on the highway.

X2 I forgot about that. I went with the TCI lockup kit, cheap but simple. I'll let you know how mine works once I finish wiring it to the switch.

 

[Mkuhn138]

Thanks for all of the info guys, I'm sure it will help streamline the swap. I hadn't considered the torque converter issue. Fortunately my brother has a tranny/tc shop and will install a hydraulic lockup for me. I'll start a thread and post photos once I get going.

Thanks again,

Matt