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TBI and 350HP?

garlicbreath

garlicbreath

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Is there anyone out there getting their factory TBI setup with mods to work with over 300HP? I have a SB350 built, and am thinking about going to injection, I can get a smoking deal on a factory 91 TBI setup complete. What would need to be done to get it to support a built 350? By built I am talking sportsman II 220 heads, RPM intake, 10.0-1 compression, .510 roller cam.
 
Do a search on here and some reading over on www.thirdgen.org . What you're hoping for and thinking of building is unrealistic with a stock TBI set up, even with a custom burnt chip. Have a read, there's plenty of interesting stuff on here and 3rd gen. It may give you ideas as to which route to take.
 
I think his setup is fairly reasonable. You will just need a larger bore tbi. Either a bored stock unit or something like a larger holley. Then some 454 tbi injectors with a larger fuel pump and a custom chip. This is how I finished off my engine and it is pretty nice.
 
iv allways been told that a factory TBI can only put out about 280 hp, but i dont know if that is true. :dunno:
 
steve_kibbe said:
I think it would be easier to swap to a edlebrock mpfi kit.
Click to expand...

Easier, but would it be cheaper? Also, I have a Holley blue pump rated at 14.5PSI would that run a Tbi? I

I'll do some studying over on thirgen, just registered last night. Good site.
 
If you want to make more power, you have to move more air. Even the Holley 670 cfm tbi unit will limit your ability to move air.

Here is the hp #'s for edlebrocks mpfi kit
Also keep in mind the other mods done to the motor.

350-3502.jpg


Holley's mpfi kit is rated at 1000cfm, but they don't have the hp #'s on jegs site.
 
As said you can do it. But you will need a larger TB and injectors manifold adjustable FPR, custom chip ECT. The thing that will cost you is getting a chip burned. Unless you can do it your self.
With your set up you will need to spend a day on a dyno with a good chip man and a hand full of chips, to get your chip burned and tuned right.
The stock chip wont support 10.5 to one CR , Sportsman heads, or your cam.
The stock TB only flows 480 CFM so you need a bigger TB. You can buy bored stock GM TBs up to 750 CFM.
I am running a 600 CFM TB on my mild built 350 and it works great. It is suppost to be able to support 340Hp.
 
Ive got a sb400 at about 360+ hp that i posted a while back about fuel injection. As it turns out Mark at Affordable Fuel Injection can hook me up with a MPI unit for just under 2G's. I was just about ready to send him a check when a few things popped up and I wil be delayed till later this year before I can get it.

The one thing that sold me on AFI's system was that they use GM parts, where if you have something go bad on the system later on you can run down to Checker Auto and get what you need.

The only challenge they may have with your engine, i think, is the larger cam. I think with your engine, TBI may be very difficult to get to run any near as well as MPI.

You can refer to page 2 of this post as well FYI
http://coloradok5.com/forums/showthread.php?t=161307&page=2

Russ
 
I think the argument here is not really whether it can be done but how much overall power do you want. Unless you have acess to a dyno the custom chip would be hard to get right. Dyno time is expensive. As has been said you can make it work but if you want every thing your engine has to offer buy a complete kit from holly or edelbrock or accel or any other FI place. Then you can mess with it almost endlessly to tune it how you want it. If you are looking for max power than dyno time is unavoidable. Good luck
 
Get a wide Band O2 sensor and burn your own chip. There is no need to spend any time on the dyno.
 
steve_kibbe said:
I think it would be easier to swap to a edlebrock mpfi kit.
Click to expand...

your talking about 1200 bucks... it may be easier but it also likes paychecks...1200 is if you already have a tbi setup... if not its about 2g's. 2g's is a lot of money but if you got it more power to you. One thing you need to know though is holley will tell you straight up the 670cfm tbi will support 350 hp but with higher fuel pressure and a good tune it'll push 400 and even more tq... I don't see his motor making anything over 380hp (probably 330) so unless he's got plans for something else to bolt onto to his motor I just don't see the need for mpfi.

Then to get it right it would need to be tuned... mail order chips just don't even come close to real time tuning.

As far as tbi goes... get a rebuilt 454 tbi or a holley 670 cfm tbi with 85pph injectors, burn a chip and get an adjustable fuel pressure regulator and a bigger fuel pump. All this might seem like alot but having bought each of these myself... its worth it. I bought a pro version of the prominator from speedtronics so I can tune and I got a 200 dollar dell laptop off ebay(you can get em from 75). Like the last post says don't bother with the dyno unless you want to know your power... you can get a wideband o2 sensor for about the same price as a few hours on the dyno.

With all the stuff I mentioned above its possible to get nearly 400 hp out of this setup and about 450 ft lbs of tq and if you get the PRO version of the prominator you can literally tune it while your driving.

Theres alot to tuning though... do some research over at thirdgen.org and get an idea of what it takes to tune a rig then decide what you want to do... tuning is not for everybody.
 
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