I just finished adding a set of Vortec heads to my 89 firebird and I am very happy with the results. It pulls hard all the way to 5500 RPM now. Now I think that my biggest problem is the stock TBI. I adjusted the fuel pressure all the way up and I ported it out for maximum airflow but I still think that I need a bigger tbi. A lot of people have been saying that you can get 260 hp out of the stock TBI but I dont think so, but maybe I am wrong. I ve even thought about just getting a carb because it would be easier to tune. Should I just get bigger injectors or step up top the Holley 670 TBI, or get a Carb? A carb would be cheaper but the 670 TBI would be more efficient if I had the right prom. What do you guys think?

 

A little while ago, I would have recommend going to carb if you are unwilling to learn how to burn chips, or use a laptop in your car. I'm going to carb, simply because I like the idea of a carbed car, and not having to sweat the little stuff, when it comes to EFI tuning.

But, under the new "Lack Of Freedom Of Speech" laws on this board (see sticky at the top concerning TBI posting rules), we're all now legally obliged to recommend TBI.

Go TBI! TBI is A-1!

Haha! Just kidding, NJSpeeder. Nothing like a little humor to lighten a situation.

 

do you have a custom chip yet?
the stock tb is capable of making plenty of power, but the ecm will hold it back if you have not done a custom chip yet.

later
tim

 

lack of free speech. LOL. nope, there were just a few people who made it WAY too much of a habit to BASH tbi. Recommend what you will, just dont flame and all the moderators will still love you.:lala:

o ya, and i would get the larger throttle body if you have time on your hands to tune. go carb if your gas is cheap, you dont drive it a lot, or you are busy all the time. it would be worth 500 bucks to have somebody tune your tbi motor after final mods were done. 20 a month in saved gas if you drive all the time pays for that in 2 years. not to mention the saved hassles if you drive it a lot.

 

Snuf's right, a 670 would be a good investment-well tuned, of course.

If you can't tune it (burn a prom, mess with injector sizes, and fuel pressure), or don't have the money to shell out for a new throttle body, AND custom tuning, then Snuf's also right; a carb is an economical solution.

As for efficiency with the stock TB versus a 670, well, it's still the same motor. Assuming that you're not running lean now, and you won't be running any more rich with a 670, then you will be using the same amount of fuel. Bigger injectors, yes, but also less stressed.

For related reading on size versus duty cycle, check out Pablo's post on the TBI horse barrier. Pablo might be strongly opinionated, but he's often got logic on his side.

 

Id defintally pick up a set of junk yard injectors or new ones if you can swing the cash. Check out Z28 Boy's page on which ones to pick up:

http://z28boy.cz28.com/tbi-fuelsystem.htm