ok here is the deal. i have a 2 bbl tbi in the car right now. it is a 89 camaro with a completly rebuilt 305 bored .030 with new flat top pistons, new crank and cam. and just swapped trannys out because the other one took a crap. its a 700r4. ive been having major computer issues with it im gettin about 6mpg right now, so im replacing the computer next week. but heres the thing, ive seen and heard alot about 4bbl carbs and want to get a holley 750. i want to no all suggestions including what intake manifold i should get with it and what the best holley 750 carb would be for the best performance from it like if i need a fuel pump esc. i basically want to no what all i need to get for this conversion to make it the best. thank you in advance for all your help.

 

What cam did you get?
Why are you getting 6mpg - Did you tune it?
Did you use the stock 305 heads? Did you port the 305 heads or do any work to them?
What is your rear gear ratio?
Why a 750 holley?
What exhaust mods have you done?
Do you have emissions testing regulations?


Your 6mpg sounds like you have something mis-matched, or you didn't try to tune the cam in.

 

it was a new stock cam but stainless steel crank.
yes the heads are stock and not ported.
i am not sure what the gear ratio is but it is not a posi so i am sure that it is stock as well, the gm stamp is on the diff.
a friend has one on his and told me that that is what i should get, someone told me to get a qaudrajet??
the exhaust manifolds are the stock cast iron ones that are really short, the pipes are y pipes 3 inches, that come into one pipe right after the manifold but there are 2 pipes coming out of the muffler. there is no catalytic converter on it. so it is loud.
i live in florida so no i have no emissions testing regulations.

as to the 6mpg, there is a computer problem i believe causing this issue. the check engine light comes on and all hell breaks lose. i have read the codes from the check engine light and 7 sensors show up bad(tps,map,maf,esc,etc....) and i think the computer is bad itself. so it is messing up the tbi and im sick of dealing with it and just want to put the best carb i can for the most power.

 

A holley 750 would be too large for a stock 305. With an automatic trans, a 600 Holley with vacuum secondaries would be much better. A non-electronic q-jet would work real well on a stock 305 also. It's more likely the Holley would run pretty well rigth out of the box without alot of tuning. In your case, since you really want to ditch the computer, you will need a mechanical/vacuum advance distributor. Again a 750cfm carb is way too much for a stock 305.

 

As stated, a 750 carb is too much, 600 is fine. Holley, Edelbrock, whatever - your choice. Also as stated, you'll need a vacuum advanced distributor - can't run a computer controlled distributor with a non-computer carb.

You'll also need:

A Mallory 4309 or equivalent return-style fuel pressure regulator. Required to use the in-tank electric fuel pump you already have. Only other option is to drop the tank and replace the fuel pump with a carb pickup and then either a) use a mechanical fuel pump on the block or b) use an external carb electric fuel pump. So as you can see, the regulator (although seems expensive) is much easier and actually cheaper in the end. This is to reduce your fuel pressure from the 12psi needed for the TBI unit down to the 5psi for a carb.

Also needed is a TV cable geometry corrector - these are specific to the carb you choose, available at Summit about $20.

Also, you'll need a new throttle cable bracket. Pick a sturdy one - there's alot of pressure on the TV cable that tends to bend cheaper brackets.

You'll also need a method of locking the torque converter. This usually requires dropping the tranny pan and installing a lockup kit, about $90 for them. But B&M makes a model that is electrically controlled based on speed, expensive at $150, but doesn't require dropping the tranny pan (I'm have no experience with these, I chose a TCI lockup kit).

Theres a sticky on carb swaps - maybe in the carb section? There's also a sticky on the torque converter lockup in the tranny section.

Good luck!

 

Sorry - the carb write up is a tech article, located here: https://www.thirdgen.org/carbswap

 

I'm running a Demon 650 and its alittle to big. I went with that just in case the 305 broke I could still run it on a decent 350. 750 would be overkill. I just did the swap and am way happier with carb tuning over tbi.