massaku

hello everyone so i have finally had it with my cross-fire injection....... i am going to switch to a carb soon. i want to know which carb and intake manifold to buy to maximize performance on my 305. i have a 82 trans am recaro edition just incase you wanted to know for some reason......

305sbc

iTrader: (3)

You probably have a 305 engine.
Most people have best results starting out with a good aluminum dual-plane intake like the Performer, Performer-RPM, or Weiand Stealth.
A carburetor in the 600 CFM range is a good match for your engine. As far as what brand/type of carb that depends on which one you feel most comfortable working with.

massaku

hey thanks for the input the edelbrock performer is what i was thinking from the start oh and the 302 was a typo lol but i have a brand new carb that i bought a couple yeas back thats been sitting in my garage for who knows how long but i bought it for my firebirds 400 so i think ill just stick that on there for the time being thanks for the tip.

five7kid

iTrader: (14)

What carb is that?

What transmission do you have?

atc3434

iTrader: (4)

The Performer isn't a bad choice, its well sized for a mild 305, its easy to work on, easy to tune, and cheap. If you have an automatic, its a decent daily driver choice - I have had very good success with mine. A quadrajet is a good choice too for daily driving. If you have a manual transmission, a mechanical seconday carb would be a better choice, for the throttle response. As recommended, an aluminum dual plan intake is a good way to go. Fuel regulator to manage the fuel pressure.

massaku

how much horsepower do you think i can get with a performer manifold and a edelbrock 650cfm??? because i am thinking of maybe sticking a 350 in there if i dont have enough horsepower.

five7kid

iTrader: (14)

The Edelbrock isn't a very good choice for a carb.

But, you can get around 300 gross flywheel HP out of a 305 with a Performer intake along with an appropriate cam, exhaust, etc.

What transmission do you have?

quick57

I would use some of the suggested dual plane intake with a 500 cfm edelbrock for ease of maintenance and daily driven use. And yes 500 cfm is plenty of carburetor for that 305 and work fine with a mild 350 as well. People are terrible about choosing way more carburetor than required.

atc3434

iTrader: (4)

The poster wants to maximize performance - I don't think the suggested 500cfm carb is the way to get there. 500cfm might be enough to support a stock engine, and you can bet you'd stay at a stock, less than 200 crank hp, output level. Increase your breathing and VE on the motor and it would be pretty easy to exceed the 500cfm limit. I agree you don't need to over-carb a motor, and that happens all the time - but 500cfm for a motor being built for a performance application would be limiting factor.

Maybe the third time will be the charm, Massaku - what transmission do you have? If automatic, is it a stock converter, or other? What rear-end gears? What other mods does the car have now as far as performance? There is a lot that can impact your carb choice, if you've got an auto bolted to a stock/mild built engine I'm gonna recommend you the previously suggested 600cfm 1406 Edelbrock, five7kid is gonna recommend you a Q-jet or any other vacuum demand based carb than the Edelbrock, and really any vacuum demand secondary carb will work well in the type of scenario. If you've got a manual transmission, five7kid will recommend something around a 650cfm mechanical secondary carb, and I would be in agreement with that. So, whats the rest of the setup on the car?

quick57

He can use the q-jet or AFB and they'll work fine. Assuming this is a stock or slightly modified vehicle. 305 ci x 5500rpm redline / 3456 = 485 required cfm

massaku

hey everyone sorry i havent checked in a while but i have an auto trans and perty much everything is stock but i plan on changing all that depending on how much horsepower i can get out of the engine.

atc3434

iTrader: (4)

Again, a 500cfm carb would suitable for a stock 305 w/ no intention of further performance modification. In your example, you're assuming 100% volumetric effeciency, which is pretty generous. A more realistic VE of 83% would put the demand at 402cfm, certainly the 500cfm carb would be adequent. Bumping the displacement to 350ci with the same VE and peak rpm would give you a demand of 462cfm, the 500cfm carb is still enough, barely. Let assume with a few changes, heads/cam, breathing mods, we're now acheiving better volumetric effeciency (assume 92%), and making our peak power at 6200rpm. The 305 now demands 503cfm, and 350 needs 577cfm. Clearly a 500cfm carb wouldn't support either motor, a 600cfm would be a better choice. (All CFM calculations were made @ http://www.4secondsflat.com/Carb_CFM_Calculator.html - pretty cool tool.)

In this particular case, the original poster is indicating his plans to maximize performance, and may even consider stepping up to 350ci motor. In that case, I would argue that 600cfm vacuum demand carb would be the best choice. If he starts off on a near stock 305, it'll still run fine - its a vacuum demand carb and he wouldn't get any of the over-carbing problems you might run into with a mechanical style carb. Further more, if he starts changing the build down the road, even stepping up to a larger motor, the 600cfm carb wouldn't quickly become a limiting factor like a 500cfm piece would.

So, a good dual plane intake manifold and a appropriate sized vacuum demand carb would work well for you. A well put together 305 can put down 300rwhp without breaking the bank too badly.

quick57

ATC3434 I agree with everything you've said all true. I'm going from learned experiences as well. A friend of mine has a 65' Chevy pickup Hotrod used strictly for Cruise-ins and car shows with a 307 and small crane performance cam. He was bound and determined to have a 650 cfm Holley VS on it. It got horrible mileage and had a terrible part throttle bog. He has little mechanical ability and wanted something low maintenence. Told him one last time to go smaller on the cfm for that engine and he's never looked back. Better throttle response all around and economy picked up as well. All depends on the purpose of the vehicle. If this is car is going to be a daily driver and he doesn't put a highly modified 305 roundy roundy 6000+ RPM screemer in it or doesn't go to a 350......i'm just saying.

five7kid

iTrader: (14)

Put a q-jet on it.

Vacuum secondary carbs are for trucks.

atc3434

iTrader: (4)

A q-jet is a vacuum demand carb - which I know you know. So I guess I don't get it, you're recommending a vacuum demand carb in one breath, and then saying they are for trucks in the next breath. I'm sure there is logic there, I just don't see it, and I don't think it'll be clear to the poster of this thread.

five7kid

iTrader: (14)

If the OP had a manual transmission, I would say get a Holley double pumper.

"Vacuum demand" is a bit of a misnomer. It's more like "flow demand", but regardless, the q-jet has economy advantages without giving up power capability that the AFB/Performer/VS carbs can't match. The Holley VS has a nasty way of keeping the secondaries open momentarily after letting off the throttle, mostly at medium throttle applications, that I particularly don't like. The Performer doesn't have any appreciable advantages over a q-jet, and plenty of disadvantages.

So, in my opinion, if you aren't going with a double pumper, there isn't any reason to go with anything but a q-jet.

And, for the record, the only legal replacement for CFI is a computer controlled q-jet, or a later type EFI.

massaku

hey thanks for all the advice everyone i think what i will probably do is put an edelbrock performer manifold and a carb in the 600cfm range whether i go q-jet or edelbrock i dont know (prob edel because i have exp. with em) but with a 600cfm range carb i can get better performance out of my 305 and when i eventually get a 350 i wont have to change alot right away.... anyway thanks atc and everyone that helped. oh and five7kid i dont ever recall legal being in my vocabulary jk