GM TBI unit size, airflow, and fuel pressure showdown

[Rocket Dog]

So I'm looking to get the TBI back on track and would like to get as much help from you guys as possible.

Here is what I have, TBI off a 94 suburban, 454. took the computer and harness, O2 sensor. Nothing else...... didn't know what else to take vs. buy.

any help you guys can give would be appreciated.

Also if anyone is in the LA, SoCal area, that can help..... it would be bonus!

Rocket Dog

[PlasticBoob]

Hey, I can help you out, but what exactly do you need to know? I had a nice little website going on off-road.com, but they deleted it randomly and without warning. I have a backup I will be putting online but it's almost a year old.

If you want to save a few bucks, take as much as you can. Air and coolant temperature sensors (cheap brand new), TBI air intake if you're not going to be putting a custom one on, HEI module if you plan on using timing control. Sounds like you're well on your way?

[PlasticBoob]

This might also help you....

[FSJ Guy]

What ECM do you have? Either Binder Planet or Third Gen forums should be able to get you started.

[ThisGuyUKnow]

http://www.viciouscustoms.com/TBI/junkyardtbi.asp.htm

they are doing a 6 cylinder but everything should be the same for a v8

[jaber]

What engine are you putting this on?
The 454 TBI, IMHO, is to big for our engines. I put one on a 425 Caddy and it was border line too much. If fuel economy is part of your goal, you should find the smaller SB TBI.
Just my .02.
The computer and harness is the same, its just the TB that is bigger.

[Jlamb]

Why do you say that Jaber? I understand that the injectors will be a bit larger and the ecm calibration is set up for the larger engine, but shouldn't the ECM should trim the additional fuel?

[FSJ Guy]

There are two general directions one can go on JY TBI installs.

Option #1: Install a system from a JY vehicle that had a motor similar to yours and adjust things such as fuel pressure, injectors and idle speed to get it to run decently on your engine.

Option #2: Install a system from a JY vehicle and reprogram the chip for your particular vehicle.

They are both valid ways of getting to the same destination. But the tips and tricks required are often different. Thus, using a 454 (2" bore) throttle body may work for one person, but not another, depending on their methods.

[blazer3664]

It will also depend on how much power you plan on making. I want to say the 5.7 TBI is good to about 400HP, and the 454 to about 500-550. More of a problem getting enough fuel flow than air from what I've read on them.

Jim

[PlasticBoob]

It will also depend on how much power you plan on making. I want to say the 5.7 TBI is good to about 400HP, and the 454 to about 500-550. More of a problem getting enough fuel flow than air from what I've read on them.

Jim

I hear the stock 454 TBI unit flows around 600-650cfm, but I could not find concrete numbers anywhere. There are also places that will bore out your 350 and 454 throttle bodies to support even more horsepower. I am personally going to switch to custom MPFI for my next 401, but boring is something else for people to consider.

[jaber]

Why do you say that Jaber? I understand that the injectors will be a bit larger and the ecm calibration is set up for the larger engine, but shouldn't the ECM should trim the additional fuel?

I shoot lower on the fuel scale. From what I've been told, it is hard to dial the 454 in to the stock 360 block.
Plus, I already have an awesome tune for the smaller one. Burn a chip and go...

[AlsChopShop]

I shoot lower on the fuel scale. From what I've been told, it is hard to dial the 454 in to the stock 360 block.
Plus, I already have an awesome tune for the smaller one. Burn a chip and go...

i've heard the same, especially from the chevy websites. that's usually why they are so cheap to come by.

Al

[PlasticBoob]

i've heard the same, especially from the chevy websites. that's usually why they are so cheap to come by.

Al

Where do you find them so cheap? I looked high and low and ended up paying $125 for mine (complete and working). This was before Craigslist, though. I saw 305 TBIs all over So. Cal. junkyards for like $20. They're the same as the 350 unit, but with smaller injectors.

Dunno about the 360, but the 454 unit is perfectly matched to my 401.

[DAHoyle]

Going to throw in my 2 cents, and that is about all it's worth.

By all means, toss in 454 throttle body. There is nothing wrong with it, and fuel flow is adjustable. I probably wouldn't run the injectors that came with it, and would step down to lower flow units. Chances are, you won't need all the fuel they provide, and there is no reason to try to tune around it. On the other hand, it can't hurt anything to have the airflow capability to upgrade, if you decide later to build a fire breather.

I drive an 89 burb, with the 5.7, and I am seriously considering stepping down to 5.0 injectors, and then upping the fuel pressure to get the flow back. I think it might help with atomization, but I don't have anything to back that up other than intuition. I'm not looking for higher than stock flow rates, just a better mixture. GM was very conservative in their fuel pressures, early on, but by the end of the TBI run, they were all the way up to 65PSI on the 5.7 in the Tahoe.

Simply put, you are pretty much going to have to make the thing run, and experiment. That means that there are no rules, other than common sense and some basic concepts. The thing to remember, is that it is not a carburetor, and you can not give it too much air. You can, on the other hand, give it so much fuel that the computer has a tough time compensating.

Give it a shot, and see what happens. Worst case, is that you have to replace it with a 50 dollar salvage smalblock unit.

[srobertsfsj]

So after reading the thread and not knowing much about what vehicles had TBI. If one were to go to the junkyard to pull a TBI setup. Obviously not one with a 454 but what vehicles should I look for?