BIGBlack87K5
Registered Member
Hey guys i was wondering if it was worth it to do a tbi to mpfi conversion and what is the best kit for it?
CK5
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tbi to mpfi
- Thread starter BIGBlack87K5
- Start date
Stomis
Professional Amateur
Yes its possible but is it worth it to you?
TBI can handle a decent amount of horsies and is simple as cake to work on. Theres a lot of guys that go TPI (Odin is one of them and hes actually from NJ) and love it. Me I'll stick with my simple old TBI.
TBI can handle a decent amount of horsies and is simple as cake to work on. Theres a lot of guys that go TPI (Odin is one of them and hes actually from NJ) and love it. Me I'll stick with my simple old TBI.
I now advise everyone looking to upgrade old Chevy engines to compare the parts cost and labor to a LS-series engine swap.
But if you want to do this conversion, the only cost-effective way I know is use a GM TPI system. The aftermarket kits are a ton of money and aren't necessarily any better. The only reason not to use TPI is if you will have extra cubes or high-rpm use.
But if you want to do this conversion, the only cost-effective way I know is use a GM TPI system. The aftermarket kits are a ton of money and aren't necessarily any better. The only reason not to use TPI is if you will have extra cubes or high-rpm use.
Stomis
Professional Amateur
LOL. TPI breathes terribly and the after market parts to help are serious dough and laughable in performance return for what you spend.
I completely agree with you though. If you have a carbd truck and you want fuel injection you cant beat TBI. If for some reason your not satisfied with TBI (which idk why you wouldnt be since it can support around 450hp) then like you said stop dicking around and take the plunge to a gen III/IV.
zombie1969
1/2 ton status
If you do a serch for performance tbi youl find some cool stuff.MPFI is better IMO but with all the performance parts for tbi out there and if your already set up for it wouldnt think the change over would be worth it and upgrading parts might be cheeper.
zombie1969
1/2 ton status
Did a quick serch and this is some of the info out there.Cool stuff.
Quote from performance site.
7.4L GM Tbi - These Ported throttle Bodies are designed for maximum airflow with ported throttle bores, larger butterflies, thinned throttle shafts, button head butterfly screws, and machined top air entrance.
Stock 7.4L GM Tbi flows 640cfm. Our's flows 720cfm. More than enough to supply over 400hp big blocks.
Im thinking about finding a stock tbi setup and using a stock 7.4 throtol body with my 355.A stock 5.7 tbi only flows something like 420cfm.Might need an adaptor plate for the 7.4 body not sure if its the same bolt pattern but seems like a easy upgrade.
Quote from performance site.
7.4L GM Tbi - These Ported throttle Bodies are designed for maximum airflow with ported throttle bores, larger butterflies, thinned throttle shafts, button head butterfly screws, and machined top air entrance.
Stock 7.4L GM Tbi flows 640cfm. Our's flows 720cfm. More than enough to supply over 400hp big blocks.
Im thinking about finding a stock tbi setup and using a stock 7.4 throtol body with my 355.A stock 5.7 tbi only flows something like 420cfm.Might need an adaptor plate for the 7.4 body not sure if its the same bolt pattern but seems like a easy upgrade.
7.4 TBI is the same bolt pattern, but you will need to either bore out the intake openings to 2" or use a spacer w/ 2" openings (not ideal as you will then step down to the smaller intake).
I say stay w/ TBI - as others have said, it is dead simple, reliable, arguably better for torque, inexpensive, and very servicable.
zombie1969
1/2 ton status
An even better idea would be to use the 7.4 body and adapt it to an Edlebrock single plain if possable.Cant loose any flow that way I wouldnt think.And would look cool as Helll.
K5dreamer
1/2 ton status
depends on what you want to do. TBI and TPI at the end of the day do the same thing. main difference, TBI has more high rpm power potential, while the runners of the TPI system have awesome throttle responce and low rpm grunt. Ive got a TPI in my IROC-Z and IMHO its one of the greatest truck motors ever made 
. a vortec headed TPI 383 would be one helluva bad a$$ truck motor. Might even tempt me to stray away from diesel powerplants.
other than that, i have to agree, for the price of an aftermarket system, youre not much farther away from an LS swap.
but.... if youre interested, there is a company ive heard good things about, mass flo efi, (www.massfloefi.com) that you might wanna look into.
. a vortec headed TPI 383 would be one helluva bad a$$ truck motor. Might even tempt me to stray away from diesel powerplants. other than that, i have to agree, for the price of an aftermarket system, youre not much farther away from an LS swap.
but.... if youre interested, there is a company ive heard good things about, mass flo efi, (www.massfloefi.com) that you might wanna look into.
zombie1969
1/2 ton status
In my case I have an 84 with a fresh rebuilt 355 and carb and would like FI but not going to buy a new system rather will pick up all the stock parts that I plan on using at swap meets here and there for cheep.An aftermarket prom chip will be one thing Ill buy new and sensors if needed.No LS swap in my future.I do plan on using my presant Edlbrock air gap intake still and will need to locate an adaptor or make one.Maybe Ill get lucky and find sombody parting one out and get all or most I need that way for cheep.Not a big rush for me just something Id like to do someday.
Stomis
Professional Amateur
Is that really what the stock 350 TBI flows at? I coulda sworn when I was f'in with my camaro that the stock TBI was like 525 and you could hop it up to 550/560 with a port and polish on the walls.
zombie1969
1/2 ton status
Just rechecked and 480cfm stock.Seems the same one is used on the 4.3 and 5.0 also.Thats the info I got off a performance site.It is just a 2brl though.The main reason I want to do sometrhing with the 7.4 unit flowing 640cfm would be perfect for me having not too big a cam and all.
Stomis
Professional Amateur
You really dont need it for just a cam and minor other stuff. I have a cam in my motor with an injector pod spacer and its fine. Dont forget you can port and polish the TB for more CFM, Injector pod spacer, and put bigger injectors in it.
And FYI the only difference between 4.3, 5.0, and 5.7 TBs is the injector size.
BIGBlack87K5
Registered Member
Thanks guys i think ill go with an ls swap when the time is right, how compatible is all the computer and wiring stuff between tbi and an ls motor?
Stomis
Professional Amateur
go read a bit at www.tbichips.com
zombie1969
1/2 ton status
Im sure it could be ported to flow better but to what?480cfm isnt a whole lot to start with.Without doing a flow bench test which I cant do Id be guessing as to what the cfm of it is.Seems it would be easier to just get one that you already know what it flows.The 7.4 640cfm would be a good all around size for a miled built 350.Not so good for my 406 that has a 1000cfm throtle body on it.If you were running a carb you wouldnt run anything less than 650 on a 350.I wouldnt anyway.The thing with FI is you can get away with a larger cfm rating than with a carb because the fuel is injected rather than relying on the flow past the bosters in a carb.
