Hot Rods Carburetor info

Can anyone tell me what carbs these are, and CFM if you know.

 

Rochester 2G 285-as much as 500
Search part# for cfms ,,,
There are small base & big base .2Gs
One's shown small base.
Those air filter covers are very restrictive

 

They look like the small bolt pattern variety that were common on Chevrolet 283s and 307s.

 

I know small base not 500 ,
Sorry for the confusion to the OP
I was just pointing out 2gs can be up to 500 cfm's ,, I have a big base 2G I believe
A one year 625 or 650 cfm ,
Olds or Buick maybe Pontiac , BB
I think 71 or 72 ,
I try to be accurate , I have so many parts over 55 years , just in carbs 45 plus. Maybe early signs of Alzheimer's?

 

I believe there are 500 CFM 2G's, but I think they're special racing versions. Years ago I ran in a cl*** that mandated a race-ready spec Holley 2bbl. When I went to buy one at Speedway, they offered the racing carb in 350 CFM and 500 CFM versions. I believe I saw 350 and 500 2G's in the same section of their race parts catalog. It's hard for me to believe that GM sold one on a car that flowed that much.

 

It's not Alzheimer's but a forgotten "black art"
The 2G series is one of my favorites to play with [taught to me by my dad] and I still get favors asked of me.
They have their quirks ,but are really simple.

The largest 2GC was 435 CFM with 1.375" venturis. [which is quite respectable in itself]
The 435 CFM 2GC has the same throat and venturi size as the Holley 2V 500 so many people claim they are 500's [especially people selling them]

You can bore the venturis out to flow better [my dad did this in the 70's] but the carb is a "dog" with low air velocity and only suitable to mid range rpm like on dirt track ovals.
There are other mods that work like thinning the throttle shafts and shortening / reshaping the boosters. [nothing that buying a 4V carb /manifold can't do better]

 

For sure but then you lose the fun of showing what you've been able to do with a "little" Rochester 2GC.

Lynn

 

Just to kick up a little memory; Anybody remember the m***ive Holley 650 annular discharge 2-barrrel?

Roger

 

Yes, didn't they have built in velocity stacks?

 

I don't remember a stack, but they did have the choke horns milled off.

Roger

 

Don't forget that two barrel carbs are rated differently than four barrel carbs.
A 500 cfm two barrel does not flow as much as a 500 cfm four barrel.

 

I remember a truck 2G with a governor, that memory (sometimes wrong) says had a 1 7/16 venturi.

I don't still have one to check, and of course the Rochester parts book do not give this information, but it was from the 1970's.

Jon