Carb size suggestions?

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Carb size suggestions?

Postby Travis73vega » Sat Mar 26, 2016 8:00 pm

I'm putting a 350 SBC in my Vega and I'm trying to determine what size carb to get. My motor is a 4 bolt crate motor, headers, Street performance intake, 270 comp Street cam. Other then that its pritty much stock. I was thinking a 650 Holley. Is that to big? What would you recommend?
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1973 Chevrolet Vega GT


Re: Carb size suggestions?

Postby Travis73vega » Sat Mar 26, 2016 8:05 pm

Sorry I didn't know that there was a category for carbs and intakes. :bang:
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Re: Carb size suggestions?

Postby cjbiagi » Sat Mar 26, 2016 8:17 pm

A 650 sounds good for a street 350 engine.
Clyde.........75 Monza 2+2
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Re: Carb size suggestions?

Postby spencerforhire » Sun Mar 27, 2016 8:01 pm

There are so many variables to consider; not just engine size and cam, but lots of other factors. Auto or stick?, If auto, how loose a converter? Gears? Daily driver or only driven to the track?
If your Vega is automatic and fairly stock other than the mild 350, the 650 CFM reccomendation is pretty well right on. An Edelbrock will probably work pretty decent right out of the box and get you better mileage and drivability. If you have a manual trans and steep gears and don't care about fuel efficiency, you probably want a Holley double pumper. Most likely take some tuning to get it right, but the car will be quicker. Might even need a 750 if you rev it high enough.
The "fleet"-
77 Vega Estate wagon- project(someday)will have TPI305/T-5, S-10 spindles/axles
72 Vega HB Drag Car -383/'Glide/9"(9.35@146.19)(5.94@117.28 1/8th)
76 Vega GT- 400/4spd/9" retired from active duty(rusty)
03 Silverado 2WD ex.cab (work truck/parts hauler)
04 Silverado 2WD ex.cab (retired)
06 Haulin' 20ft enclosed car transporter
93 Suburban- 350/4L60(retired)
00 Saturn SW2- wife's car
01 Saturn SC2- younger son's project
00 Saturn SL2- daughter's car
98 Saturn SW2- spare
and 3 more Saturn "parts cars"
Note- the very act of listing all of these has made me realize I have some kind of problem.....

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Re: Carb size suggestions?

Postby Travis73vega » Mon Mar 28, 2016 7:47 pm

spencerforhire wrote:There are so many variables to consider; not just engine size and cam, but lots of other factors. Auto or stick?, If auto, how loose a converter? Gears? Daily driver or only driven to the track?
If your Vega is automatic and fairly stock other than the mild 350, the 650 CFM reccomendation is pretty well right on. An Edelbrock will probably work pretty decent right out of the box and get you better mileage and drivability. If you have a manual trans and steep gears and don't care about fuel efficiency, you probably want a Holley double pumper. Most likely take some tuning to get it right, but the car will be quicker. Might even need a 750 if you rev it high enough.


Im going to look into the 650s and see what I can come up with.
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1973 Chevrolet Vega GT

Re: Carb size suggestions?

Postby cjbiagi » Mon Mar 28, 2016 9:29 pm

I am running the Edelbrock 650 and have been very happy with it on my 350
Clyde.........75 Monza 2+2
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Re: Carb size suggestions?

Postby EVL VEGA » Tue Mar 29, 2016 1:26 pm

A few google results. These should get you close. Just don't fall victim to the bigger is always better when it comes to carbs. My benchracing friend tried to talk me into a 1050 dominator. That is WAY too big for my mild pump gas 406. I run a Holley mechanical secondary 750 double pumper. It's set up for racing and not for street so i only get about 6mpg.

http://www.hotrod.com/how-to/engine/1408-how-big-a-carb-do-you-need/
http://www.summitracing.com/expertadviceandnews/calcsandtools/cfm-calculator
http://www.gtsparkplugs.com/CarbCFMCalc.html
http://www.4secondsflat.com/Carb_CFM_Calculator.html
http://www.pro-system.com/pjames011900.html
http://www.wallaceracing.com/intakecfm.php
EVL VEGA
'73 Vega Hatchback (former Super Gas car)
406 SBC, AFR 210 Eliminator Heads, 9:1 comp, pump gas, 328RWHP/412RWTQ (old heads, no N2O 1/17/04), 6.86 @ 100.8 in 1/8th (No N20 9/4/16), Mike's Trans TH400 (reverse manual), 5000 stall, 12 bolt, 35 spline strange axles, 4.33 gears, spool, hipster transbrake, linelock, backhalved, Alston 3 link, 100 shot NX Hitman+ kit, LC1 Wideband sensor, 31x18.5 MT Sportsman Pros, "Plum Ugly"™ Purple paint.
"Pound to fit..paint to match"
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Re: Carb size suggestions?

Postby spencerforhire » Tue Mar 29, 2016 6:05 pm

It is actually pretty hard to over-carburate a drag race engine. They will often go quicker with a carb 10-20% too large. The engine can only take in what it needs; all that happens at WOT with a too-large carb is a drop in velocity as the vacuum reaches zero. My 383 which I consider "mild" as race engines go, works best with a 950cfm Holley HP. The math says I only need something like 910 CFM to feed the thing at 7800 RPM.
The "fleet"-
77 Vega Estate wagon- project(someday)will have TPI305/T-5, S-10 spindles/axles
72 Vega HB Drag Car -383/'Glide/9"(9.35@146.19)(5.94@117.28 1/8th)
76 Vega GT- 400/4spd/9" retired from active duty(rusty)
03 Silverado 2WD ex.cab (work truck/parts hauler)
04 Silverado 2WD ex.cab (retired)
06 Haulin' 20ft enclosed car transporter
93 Suburban- 350/4L60(retired)
00 Saturn SW2- wife's car
01 Saturn SC2- younger son's project
00 Saturn SL2- daughter's car
98 Saturn SW2- spare
and 3 more Saturn "parts cars"
Note- the very act of listing all of these has made me realize I have some kind of problem.....

Visit http://www.spencerforhire.ca
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Re: Carb size suggestions?

Postby beakerztoyz » Sat Apr 02, 2016 11:21 am

these guys have given good suggestions, on a mild smallblock I'd run something between 6 and 650 cfm, I'd shy away from going to a double pumper or going bigger unless its a race motor or it has high compression or something. I think right now the edelbrock on my mild smallblock is a 625, I'm not a huge fan of them but they're decent if you just want something to bolt on and not mess with. I think carb's are kind of application and people specific, depends on weather you like to tweak it fairly often or not. and it depends on what you want the vehicle to do.
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1980 monza spyder.... v8

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