questions about tbi build

Printable View

03-09-2013
4thgentruck

questions about tbi build

Im building a sb 400 . My friend threw the idea to me about running a tbi set up which id love to do. My questions are would it be best to run a 350 tbi or 454 tbi?

Also heard you can only go so big on your cam?

How big of a head ache am i lookin at?

My build 400 bored .030 over
Stock crank
Stock rods
Flat top pistons
Crane hmv-278-2 cam duration 278/290 lift .467/.494
Stock 997 400sb heads
Roller tip rockers
Edelbrock performer intake.
Long tube headers for 77 chevy truck

Any advice would be super thank you
03-09-2013
dave w

Quote:

Originally Posted by 4thgentruck

Im building a sb 400 . My friend threw the idea to me about running a tbi set up which id love to do. My questions are would it be best to run a 350 tbi or 454 tbi?

Also heard you can only go so big on your cam?

How big of a head ache am i lookin at?

My build 400 bored .030 over
Stock crank
Stock rods
Flat top pistons
Crane hmv-278-2 cam duration 278/290 lift .467/.494
Stock 997 400sb heads
Roller tip rockers
Edelbrock performer intake.
Long tube headers for 77 chevy truck

Any advice would be super thank you

The 454 Throttle Body is 670 CFM, the 350 Throttle Body is about 535 CFM.
If your an expert TBI tuner, the cam you have will not be a problem. If your new to TBI tuning, the cam you selected will be a HEAD ACHE!:mad1:

dave w
03-09-2013
4thgentruck

I was gonna build it and take it to a local shop that tunes tbi's. I bought the motor for 200 dollars and was gonna get the tbi and intake. Everything else was already there. Tryin to get out as cheap as possible. And we have a local junk yard called u-pull-it which is just that i would have to go pull the parts off myself. Which i would label the wires as i took them off and keep the old parts in the plugs and just buy newones when i install them in my truck. Doing a complete ground up resto .
03-09-2013
EagleMark

You can go as big as you want with a cam and EFI.... if you want to run Open Loop and take the time to tune it with a Wide Band O2 sensor.

But the real question would be what is this truck going to be used for? What transmission? What I'm getting at is it's not going to idle at 600 RPM and the rating is from 2500 RPM to 5500 RPM. Most street vehicles at normal driving is all under 2000 RPM... SO in a manual trans with some high gears it would be OK. Auto trans would need a high stall converter and high gears. Hope fuel milage is not a concern?
03-09-2013
4thgentruck

That was the whole reasoning behind the tbi was to get better fuel economy. Ill be running a 700r4 trans and right now the gearing in the truck is 4.10 i was going to switch it out to a 3.73 gearing. It will be used as a daily driver. Not hot roding but would like it to go when needed.
03-10-2013
mrmarty51

find a 88 or newer Suburban,the wire harness in the "Square body" Suburbans is way more simpler than the 89 or 90 GM pickups.
If Your GM vehicle is of the "Square Body",73 to 88 model years then also pick the "Complete Dash Unit" from the Suburban as You will need the electronic tach too.There is an adapter found here that can be used instead of changing out the dash unit if that is what would be more desireable to You.
http://www.jagsthatrun.com/Pages/Spe...eedometer.html
Please,someone,correct Me if I am wrong.
The big block TBI can be run on the small block,I`m told that the smaller SB injectors should be used for this.I am not certain but there might be a wind velocity difference between the BB TBI that might create some problems.That is the windage going down the airhorns.
On the gearing,I would,if it were mine,keep the stock 4.11s or .10s whichever they may be,until after the 700 trans is installed and see how the overdrive decreases RPMs with Your lower gearing,try it out before going through all the labor/hassle of swapping out gearing.I have the 3.73 gearing in My 93 GMC and am mostly in town but do on ocassion pull a 17,000 pound tandem axle trailer and My thoughts are,while pulling the trailer,that I think the lower gearing could probably help Me from running out of power in the hills and help the 700 trans out a lot by not having to do so much nshifting,probably increase fuel mileage whilst pulling too.
I too have a SB in a 93 GMC that I am thinking,one of these days I will be needing to do some work on,248,000 miles,and would like to do a bit more of a cam in this one too so I will be watching this thread.
03-10-2013
EagleMark

I'd keep the 4;10 gears as well. My 90 Suburban has 3;73 and does well on tiny tires, 235 75-15.

There's all sorts of good cams for these type rigs. The one OP posted isn't one of them. Even a LT1 or Vortec cam is a good choice, I'd never waste money on a new motor without roller cam nowadays. Hard and expensive to find oil for flat tappet cams.

He can run the BB TBI on that carb intake with an adapter, but to put a BB on a SB TBI intake it has to be machined bigger to fit. Injectors from the BB can be used and a good upgrade while doing cam and head work so you have enough fuel. There's really not enough from 5.7L Injectors for a stock motor. More pressure helps to a point where bigger injectors are a better option.

Not sure what the 400SB heads will breath? If your not going to port them, then find a cam, intake etc... accordingly to match.
03-10-2013
dave w

2 Attachment(s)

Quote:

Originally Posted by 4thgentruck

That was the whole reasoning behind the tbi was to get better fuel economy. Ill be running a 700r4 trans and right now the gearing in the truck is 4.10 i was going to switch it out to a 3.73 gearing. It will be used as a daily driver. Not hot roding but would like it to go when needed.

The 454 Throttle Body needs to be modified to work with a 700R4 TV Cable. I think the pics below show what's needed to be done.

dave w
03-11-2013
mrmarty51

Quote:

Originally Posted by dave w

The 454 Throttle Body needs to be modified to work with a 700R4 TV Cable. I think the pics below show what's needed to be done.

dave w

I "think" there is some years that have the TV cable fixture that is the right one,"BUT" I thank You for showing us the mod. that needs to be done to make them work as it seems that the proper TBIs is hard to come by.
03-11-2013
EagleMark

I don't think the 700R4 ever came behind a BB? Never saw a BB TBI with the TV cable. There are some kits for it. I rebushed a BB TBI once and used the SB shaft with TV cable point.
03-11-2013
mrmarty51

Quote:

Originally Posted by EagleMark

I don't think the 700R4 ever came behind a BB? Never saw a BB TBI with the TV cable. There are some kits for it. I rebushed a BB TBI once and used the SB shaft with TV cable point.

OK,I am not aware of what transmission a BB would have used,TH400?
I do`nt have a reamer to do the reaming properly but maby a drill bit would do,and then have a machine shop make Me up the bushings then use the 350 TBI shaft.
03-11-2013
EagleMark

Yes they came with TH400.

If you don't need bushings it's probably easier for the kit or weld one on like Dave's. My buddy has a machine shop so it was easy...
03-11-2013
dave w

Quote:

Originally Posted by EagleMark

I don't think the 700R4 ever came behind a BB? Never saw a BB TBI with the TV cable. There are some kits for it. I rebushed a BB TBI once and used the SB shaft with TV cable point.

The 700R4 was not a factory option with the 454 TBI engine, so are no factory original 454 Throttle Bodies that have the TV cable bracket. The 1993 and newer SBC throttle bodies do not have TV cable brackets because the 700R4 was replaced by the 4L60E.

dave w