I need some advise... Should i put a 750 cfm 4 brl carb on a 305 engine or would that carb be too much. if it is, what size should i put on a 305 engine????? thanx

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Benji

Almost this very question was asked on this post https://www.thirdgen.org/messgboard/...ML/000800.html .

The stock q-jet flows anywhere from 650-795 cfm, depending upon the original AV opening stop. It can be modified to give full opening (see tech articles). The q-jet is very versatile, however, working well on engines needing only 550 cfm as well as engines needing the full 795. The same cannot be said about square-bore carbs like Holleys and Edelbrocks.

For a street-driven car, the best bet on a 305 is the good ol' q-jet. Work with it, you'll be better off for driveability and economy for the money spent, with no sacrifice in power.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam and intake, World 305 heads, Hooker headers & y-pipe, 3" Catco cat & 3" cat-back).
57 Bel Air, my 1st car. 0.030 over 396, 9.7 CR forged TRWs, Weiand Action+, Edelbrock 1901 Q-Jet, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlock header mufflers, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, LT MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1/95.5 @ 5800' Bandimere.

Hey I think that a Demon 1100 would be right up your alley, if not shoot for a holley 600 (EAS) or maybe just a strong rochester quad jet they are a very solid carb

A 750 cfm on a 305 can be made to work if tuned correctly.

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383 86 Camaro Z28
10.5:1compression Dart Pro 1 Aluminum heads 215cc>2.05/1.60 valves,400 steel crank,cam specs:234 dur at 050 488/488 lift,2500 stall converter,shift kit,3.42 gears,770 Holley Avenger,Victor Jr. Intake,true dual exh,Hooker headers with 40 series Flowmasters,MSD Coil and Module.

[This message has been edited by Big454blockchevy (edited June 27, 2001).]

[This message has been edited by Big454blockchevy (edited June 27, 2001).]

since a 350 only really needs a 650 cfm, why bother with a 750 on a 305?

Get a 600 VacSEC and be happy.

Need I find the formula's?

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86 T/A 5.0 A4 & 2.77 gear
15.62 @ 86 mph
93 Civic 1.6L
13.5 @ 100 mph

Those formulas really don't match up your engine with a carb to good. Ignore those formulas. According to the formulas I am supposed to be running a 600 cfm carb. I think not!!

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383 86 Camaro Z28
10.5:1compression Dart Pro 1 Aluminum heads 215cc>2.05/1.60 valves,400 steel crank,cam specs:234 dur at 050 488/488 lift,2500 stall converter,shift kit,3.42 gears,770 Holley Avenger,Victor Jr. Intake,true dual exh,Hooker headers with 40 series Flowmasters,MSD Coil and Module.

yea and it said my cammed 350 only need 300 cfm

I don't trust that formula.

What formulas are you guys talking about? The ones I always use go: engine (displacement X maximum RPM)/3456

It works everytime and for a 350 that only runs to about 5500 to 6000, 650cfm sounds about right. As far as 300 cfm for any V8, Id like to know who told you that.

Transam383 a 650 would no doubt work on a 305 but a 750 Correctly tuned will work just as well. I know I've tuned a 750 on a 305 before and I like the response of the 750 better thatn the 600cfm.

[This message has been edited by Big454blockchevy (edited June 30, 2001).]

First off I am just curious, no disrespect intended, what type of carb was it and what did you have to do to it to make it run right? I was hoping to get a new carb that I could run for now on my L-69 and then just swap onto my 377 once its built. I figured I would just have to have 2 different carbs.

I think a 750 Holley vac sec. would work on both engines with tuning for each particular engine . As far as tuning each engine is diffent and you would need to go about it the hard(or correct) way which is reading the plugs and going accordingly. Maybe you could start with 62#jets on primaries and 68 jets on secondaries for your smaller engine.

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383 86 Camaro Z28
10.5:1compression Dart Pro 1 Aluminum heads 215cc>2.05/1.60 valves,400 steel crank,cam specs:234 dur at 050 488/488 lift,2500 stall converter,shift kit,3.42 gears,770 Holley Avenger,Victor Jr. Intake,true dual exh,Hooker headers with 40 series Flowmasters,MSD Coil and Module.

Well if that equation is true then I should be running a 526 cfm carb., is my 600 cfm too much, if that why the car is running rich?

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'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
FLOWMASTER
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat
2:73 GEARS
Rebuilt 700R4, with manual valve body
B&M Megashifter
Soon to be installed
Exhaust Cut-Out and different gears, either 3:73 or 3:42
"There is nothing more addicting than speed"

no that formula is horse ****. You are running rich either because your choke is sticking, your A/F mixture is wrong or you might even have bent metering rods. It can happen because it happened to me. If the carb is taken apart and not carefully put back the metering rods will bend and not go in the jets.

The formula is great on paper but real world testing shows that the cars are faster down the track and there is no difference in gas mileage. A 600 can actually get worse mileage if it is tuned wrong.

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I WOULD RATHER PUSH A CAMARO THAN DRIVE AN IMPORT

1983Z28 350w/ edelbrock performer RPM power package , dynomax shorty headers, 700R-4 with shift kit, 750cfm carb, edelbrock 3" exhaust system, ASCD SS hood, 16" IROC rims.

future mods:
completely done over suspension, black paint with flames, Hurst shifter, dakota digital gauge package, procharger supercharger.

Well I know the choke isn't sticking because I took it off for the summer. My A/F screws are probably out of whack, I have no idea where they should be I did full with them a little and it helped mpg a little.

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'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
FLOWMASTER
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat
2:73 GEARS
Rebuilt 700R4, with manual valve body
B&M Megashifter
Soon to be installed
Exhaust Cut-Out and different gears, either 3:73 or 3:42
"There is nothing more addicting than speed"

this is how you adjust them on an Edelbrock carb: turn the screws all the way in (don't torque them down because you will ruin the seats) then unscrew them 1 1/2 turns and hook up a vacuum gauge to the driver's side vacuum port and start the car and set the idle to 800 RPM's. then turn out the screws evenly until the vacuum gauge stops rising. Once it stops turn them in a little and then readjust the idle because it will probably be high by now. Then you are done.

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I WOULD RATHER PUSH A CAMARO THAN DRIVE AN IMPORT

1983Z28 350w/ edelbrock performer RPM power package , dynomax shorty headers, 700R-4 with shift kit, 750cfm carb, edelbrock 3" exhaust system, ASCD SS hood, 16" IROC rims.

future mods:
completely done over suspension, black paint with flames, Hurst shifter, dakota digital gauge package, procharger supercharger.

You have to continually adjust the idle speed, not just when you're finished.

a 750 on a 305 is a little much, plus do you plan on having this car as a daily driver because i can assure you that 750 will get terriable gas mileage