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Old 05-23-2013, 08:20 PM
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Another "Help me pick a carb" thread

I know there's probably a million of these, but hey every car is different.

Right now I have a 1980 Firebird. Engine is a Chevy 350 bored .60 over with 041 heads that have 2.02 1.6 valves and have been ported. Cam is an Elgin with what I think is a 488/508 lift, but the crappy part is I have no idea of the duration. Intake is an Edelbrock Performer RPM. Compression is around 9:5 so I can run it on pump gas.

Trans is an auto th350. Rear end is a 10 bolt posi 3.42. Car weighs about 3,700lbs with lots of suspension mods to make it handle like a modern car.

Right now I have an Edelbrock 650cfm. Just a bottom line plain carb. It stumbles a bit off the line. I want to just get a whole new carb and I want a Holley. I was told a Holley 750 Double Pumper with mech. secondaries would be the best for power. Which is what I want, who doesn't? But the car is really just meant to be a fun street car and I also want driveability so I was thinking about a Street Avenger. Gas mileage isn't too much of a concern because if I was worried about that I would just get a Honda.

So Double Pumper vs Street Avenger for max power, throttle response and driveability? What cfm for my setup?
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Old 05-23-2013, 08:40 PM
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I dont like S.A. carbs.If you want a double pumper ,,,a 650 or 750 is a great carb.It takes a little tuning and most dont have a choke.

maybe buy a kit and tune the 650 you have?
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Old 05-23-2013, 09:08 PM
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I agree with Vinnie, everything I have heard about the SA carbs is not great with big duration cams, which at 234/244 @.50 yours is.
Its a heavy car with not alot of gear, so conventional wisdom would say a 750VS would be the way to go.
But there's more too it then that, you mentioned a bunch of suspension to make it handle, so i don't suspect it has the usual 275DR out back.
If its set up to handle lets say it has a 275/40 17 on it, a fairly standard F-body performance size vs a street strip tire (DR) say 275/60 15
So now your effectively adding gear to it by using a short (25.66) tire
instead of the 28" drag radial.
add a 3000stall which you likely have or need for that cam, and now I believe a 750DP is the way to go.
Of course I think and assume way too much occasionally.
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Old 05-24-2013, 10:44 AM
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Quote:
Originally Posted by valtiel43 View Post
I know there's probably a million of these, but hey every car is different.

Right now I have a 1980 Firebird. Engine is a Chevy 350 bored .60 over with 041 heads that have 2.02 1.6 valves and have been ported. Cam is an Elgin with what I think is a 488/508 lift, but the crappy part is I have no idea of the duration. Intake is an Edelbrock Performer RPM. Compression is around 9:5 so I can run it on pump gas.

Trans is an auto th350. Rear end is a 10 bolt posi 3.42. Car weighs about 3,700lbs with lots of suspension mods to make it handle like a modern car.

Right now I have an Edelbrock 650cfm. Just a bottom line plain carb. It stumbles a bit off the line. I want to just get a whole new carb and I want a Holley. I was told a Holley 750 Double Pumper with mech. secondaries would be the best for power. Which is what I want, who doesn't? But the car is really just meant to be a fun street car and I also want driveability so I was thinking about a Street Avenger. Gas mileage isn't too much of a concern because if I was worried about that I would just get a Honda.

So Double Pumper vs Street Avenger for max power, throttle response and driveability? What cfm for my setup?
The carb needs to meet some expectation of engine power, so you really need the cam specs and some reality about what the compression ratio is both the static and the dynamic.

My first cut at these things is for an 350 making less than 350 horses a 650 CFM will suffice and a 750 is overkill, this should be a vacuum seconday type. For a 350 making above 350 horses a 750 is needed. Between 350 and 380 horse the vacuum seconday is fine, from 390 on up a mechanical secondary.

I have no probem with the SA for a hot street engine it brings some nice toys to the game with real metering blocks front and rear, center mount floats, vacuum secondaries, 4 corner idle, and a choke. whether this is max power or not I don't know that depends a lot on how you use it and the installation; but this carb goes a long way to bridge the needs of a street engine while giving the flexability and some nicer features of a competition carb's adjustability.

Bogie
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Old 05-24-2013, 04:01 PM
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http://www.summitracing.com/parts/su...50vs/overview/
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