I've got an '89 IROC with a 305 tbi in it.. if I were to go up to a 350, would the stock tbi flow enough for the 350? Someone once told me it wouldn't. And if it wouldn't.. would one of those Holley 650cfm tbi's you see in Jeg's work?

I'm also assuming if I were to do something like that, I'd need to change a few other things.. like possibly the computer chip?

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89 iroc-z 305 tbi
everything stock, except for a mirror that fell off

 

You can put a 406 under the 305 TBI. It doesn't matter. It'll start and drive. Will you get the power you probably expected ? No. That's the only reason people say it doesn't flow enough. As far as I know, it doesnt flow enough for a 305 either. Hehe

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92 Z28 L98 350
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Ported stock heads, XR270HR-10 cam, TES headers, Crane AFPR, Flowmaster catback, MSD ignition components.
Best ET 13.5@105 mph
"Take that auto, drop it in first, hold the brakes, stomp the gas and grin from ear to ear! :-)
Click here to see my car at Truspeed.org

Check out TruSpeed at http://www.truspeed.org
Check out the Bin Archive at http://www.truspeed.org/bins.html

 

Yeah, what Blade said. A custom chip or a sizable bump in fuel pressure will help make the most of the combo but to answer your basic question, it will be a point of restriction on even a fairly mild 350.

 

If you were gonna do that, I'd get Holley's TBI which flows 670 CFM. That's a lot better than the stock unit which is a little more than 400 CFM. The Holleys come with bigger injectors, and a custom chip is needed with the bigger injectors or else you'll be running very rich. I'd set my fuel pressure to whatever the Holley injectors are rated at so when the custom chip is made they'll know how much fuel you'll be shooting into the engine.

Hope this helps,

Jason

 

Another thing you could do if you wanted to save some major dough, and still retain a factory type setup is get a throttle body from a Chevy TBI pickup. They came with 350's in them. I've seen quite a few people go through hell trying to dial in those so called "universal" throttle body setups offered by aftermarket suppliers. Hey Enkil, speak of the Devil, go check out Mike 92's post on the TPI board. He was telling everyone he put a Holley projection on his car and hasn't been able to tune it right for several months now. I just noticed that post and figured I'd throw it in as a testimonial of what a PITA those aftermarket setups are!

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89RS w/350 TPI; 69RS/SS w/450 HP 350/Muncie 4-Speed "Too weird to live, too rare to die."

[This message has been edited by Pat Hall (edited December 28, 2000).]