Hey guys, I've got a quick question for anyone who wishes to put there 2 cents in.

I stumbled across my car this summer when I was driving down to get some dinner. I've only had it for about three weeks so I haven't had the chance to do much with it yet. It's a 92 Camaro RS, the car is in amazing shape (heritage kit and all) but the only downside is that it has the 2 barrel TBI 305 under the hood. The only thing that I have really done so far is install my B&M shift kit. (Which I did with not a lot of extra help I might add).

Anyways, here's my question. Is it worth my time to convert this slow 2 barrel TBI to a Holley 4 barrel Carb. What are the ups and downs, and is it something worth attempting myself? I know that there is ECM work involved and that the intake manifold is going to have to be changed. Have any of you guys thought about this or attempted it on your own? Anything you guys have to say would be a big help.

--Pat

 

A carb would allow for more airflow, but having a computer controlled motor is nice. There are alot of other mods you can do to a 305 TBI motor. Holley offers a 670 TBI unit that flows real well. All though a LO3 doesnt need the tbi changed first. The biggest bottle necks on our motor is cam, heads, exhaust manifolds, intake, and tbi. The stock tbi can be made to handle around 240 hp, so I would read up on some other big mods to do first.

Check sig.

Full exhaust, free tbi mods, headers, intake, cam, heads, 3.55 or 3.73 gears in that order give or take a few

 

Actually the stock TBI has seen 300 HP on a dyno. Do a search on a guy named fastbroker.

 

even the stock 2 barrel TBI?

 

Yes. It would be a mistake to just slap a 4bbl carb on there now. The 2bbl TBI unit is not what is keeping you from making power at this point. That 305 is restricted mostly by the full exhaust, then by cam and intake, and by the heads as well. Get headers with full 3" exhaust then get 3.42 or 3.73 gears with a posi carrier and an intake and cam after that. At that point you might be nearing the point where the TBI unit has become a big restriction. Too many people think that slapping a big carb on there will solve all your power problems, you'll be disappointed if you put a carb on that stock engine how it is now.

 

You nailed that! Its unbelievable how much headers and full exhaust helps a otherwise stock LO3.
With my mods, a 1 11/16" (ultimated) TBI is feeding me to redline(6000) with no restriction. I have data logged the MAP at WOT to 6000 rpm's several times on my laptop.
I'm sure a 350 needs a 2" bore TBI but I have a hard time reading all this crap about people needing one on thier 305, because I don't need one with my mods.

 

Quote:

even the stock 2 barrel TBI?

That depends on what you consider stock. In its factory form, a TBI off an L03 will not handle 300HP. Look on the main page Tech Articles for the "Ultimate TBI Mods". These mods alone will unleash a few HP and increase flow appreciably. Pair these mods with larger injectors and possibly even the larger 2" bore Big Block TBI or the Holley TBI and you can feed over 300HP easily. As mentioned, going to carb is not the answer. They require constant tuning with changing conditions and are a PITA. If you enjoy that kind of thing, more power to ya. Me, I'll take a TBI system that is good from below sea level to the highest altitudes, and sub 0 degree weather to the hottest inner city driving condidions without so much as turning a screwdriver.

 

Actually it was a un modified 1 11/16" tbi with stock 45 lb injectors running at like 32 lbs of fuel pressure if I am recalling corectly. Do a search. I didn't write the thread, I only read it. Most of the people on this board are only speculating. Fastbroker actually did alot of dyno time trying to get it right.

 

45# injectors at 32 p.s.i. is not exactly stock. Quadrupling the fuel pressure doubles injector flow so 45# injectors @ 32 p.s.i. will flow at around 90# which will support around 300HP. I agree with you JokerRS, a standard bore TBI is plenty for most L03's (read 99%), but would make a lot of modded 350's fall flat on their face at higher RPM's. I was merely trying to educate our carb happy friend on the potential of TBI. I would never lead anyone astray on mere speculation and I would hope that it would never happen to me. Opinions are one thing but is a whole other story.

 

Thanks for all of the info guys, exactly what I needed to know. Now it's just a matter of figuring out the right order to start doing things in. I am thinking exhaust, and headers first and then working my way up from there.

 

Thats a real good place to start. Good luck.