Ditching the TBI for carb...
 

I have an 87 Silverado 4x4 with the 350 tbi and lock up 700r4. Trans was rebuilt and beefed up a couple years back, but the motor is getting in need of a freshen up. With that said if I tear this thing out this summer I'd like to dump the TBI and build something up a little that would give more smiles per miles per say. Dug around the last 45 minutes on the web with not much solid advice besides don't do it.

Soooo what does a guy need to know? Another question is the 700r4 in the 87 computer controlled? Would I be better to swap say a 350/400 turbo in, if so how extensive is that?

Thanks in advance!

Re: Ditching the TBI for carb...
 

I'm assuming you don't have emission checks there? If so, how you going to get around it?

Re: Ditching the TBI for carb...
 

No emissions check.

Re: Ditching the TBI for carb...
 

I also advise against it, unless it is trashed and not working. I think you will not be gaining anything if you do dump the Tbi. Sure, you can tune, and do all kinds of stuff to carbs, but some engineer took all the guesswork out of it and put tbi.

Oh and the 700 is not computer controlled.

Re: Ditching the TBI for carb...
 

Appreciate the two cents but all due respect, that's not what I'm after. Fwiw I've had troubles with it in the past and this tbi has been the number one problem truck I've ever had out of a dozen or more. I think I've figured it out problem wise but as I said if I tear it apart I'd like to build something.

Re: Ditching the TBI for carb...
 

I want to add to the above about the 700r4 - the computer does control part of it - the electronic converter lockup is controlled by the ECM.

Keith S may know more about you would lose/keep when you remove the TBI system. I considered it when I swapped to a rebuilt 350 with all different parts since TBI is very picky on what it likes. In the end I didn't want to lose my Cruise, A/C high idle & 700r4 Lockup which all run through the ECM and talk to the TBI system to get their parameters on when to do things.

I went with the Dynamic EFI system which seems to work pretty well. I added the Holly TBI in place of stock as well which normally will give fits on the stock ECM, but the Dynamic EFI system can control it - it works very well.

Re: Ditching the TBI for carb...
 

While I'm not sure on the 700r4 stuff. But I got rid of my tbi for a quadrajet and in my opinion it was one of the best things I've ever done to this truck. You'll need an intake, a carb of course, HEI distributor, and a fuel pressure regulator. My A/C still works, don't have cruise so not sure on that.

Don't worry I also had a lot of tbi Lovers telling me what a horrible idea removing the tbi was.

Re: Ditching the TBI for carb...
 

I should clarify - the A/C will still work, but the high-idle when its on will be lost.

Re: Ditching the TBI for carb...
 

Some engineer took all the guesswork out of it for 1 specific set-up when discussing OE TBI systems. Change that set-up & you have to 'tune' things just like you would for a carb. Tune a carb & tune a factory TBI set-up then get back to us which was easier.

That being said, I wouldn't necessarily just throw on a carb though. There has been recent development by multiple manufacturers for retrofit TBI set-ups that adapt to various combos, self tune using technology developed long after TBI's were new, and that don't cost an arm/leg.

Re: Ditching the TBI for carb...
 

Carbs had AC idle solenoids that would adjust the idle automatically when the AC is in use. It was available since the early 70's.

Re: Ditching the TBI for carb...
 

Thanks, what did you do about the ECM, unhook it and call it a day?

Re: Ditching the TBI for carb...
 

Yup, pretty much. There were a couple of wires I had to splice together for the fuel pumps. If I'm remembering correctly.

Re: Ditching the TBI for carb...
 

Im pushing 320hp and 400tq from my 87tbi 350 silverado. Have a comp cam 90350 truck avenger camshaft,454 throttle body with 90pph injectors and 18psi fuel pressure springon a bored to match Edelbrock intake manifold, .060 over with 9.8:1 compression, and stock 89 heads. Yes i am limited to about 5000rpm because of the heads but the biggest problem with the tbi engines is the pathetic stock camshaft. Lots of low end torque amd very fun to drive as well as good as a daily driver, reliable.

Re: Ditching the TBI for carb...
 

Swap the carb on, wire in the lockup for the convertor manually or using a bowtie overdrives setup like I did with my 200-4R and it locks up in 4th automatically.

Re: Ditching the TBI for carb...
 

Under 400 hp - stick with the tbi. It is a great setup, if already equipped I would spend the time to get it working for you. Just my 2 cents.

Re: Ditching the TBI for carb...
 

here is my two cents worth,

Started with a stock 1991 4300 pound Chevy truck with TBi, and about 16 mpg, then added injector spacer, and throttle body spacer, and a super hot coil, a set of headers, it went from the 16/17 to 21 to 24 miles per gal. on 89 octane, for what ever reason it seemed the coil made the biggest difference, every other week i drove from Houston to Denton Texas, at around 300 miles one way, so to experiment I would drive with windows down and A/C off, with factory coil, then hook the hot coil up, with out A/C and then with..ect ect.. the best thing about it was that there was no choke worries on a cold day, and it was super reliable, and idled smooth,... I have a stock 1981 Chevy with 4 barrel carb, and other than the killer sound it makes when you flip the breather over, it never can match my 91 for reliability and fuel mileage,

Re: Ditching the TBI for carb...
 

I have no complaints about Quadra-Jets or TBI. That's why I leave what came on the vehicle.