gm rochester 2 jet adjustment?

got a rochester 2 jet temporary on my truck need to know where the mixture screws are and rough adjustment and can i throw away those things that stick out of the sides on the top of it?any photos please would help........Marq

 

Screw in one screw until engine stumbles, screw out 1 1/2 turns. Repeat on other screw. Have no idea what those things that stick out the sides of the top are - picture would help.

Mutt

 

those sticky out things are vacuum bits but they aint connected,i think they are to do with emmisions or sommit.........marq

 

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those sticky out things are vacuum bits but they aint connected,i think they are to do with emmisions or sommit.........marq


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Just block the va***m thingys off. The idle screws are on the base plate.

Nuthin' wrong with 2Gs I got three of 'em I'm running on the old chrysler.
Easy to tune and dependable as a hammer.

 

Paul, remove everything except the throttle linkage, you will have to sprag the little fast idle cam closed that the tickover screw pushes against, if you remove anything and it pulls air you will need to plug it, I use little self tappers with fibre washers on. KT.

 

i got to say they look like a nice big carb that could handle a large engine with multiple carbs(Kerry make a note more 2 g's for the 392)they also look reliable,anyone know what cfm they can flow?.......Marq

 

marq
Leme dig my book oout and I'll tap out the CFM rateings and the conversion so you can comare them to a 4bbl carb (something everyone understands?).
It'll take a minute.
The really aren't that big a carb they just look big. But they were used on Olds and pontiac tri power setups (big block motors).
Back in a flash.

Here ya go.


Rochester 2G 11/4” flange 17/16” throttle bore
13/32” venturi 278 CFM

Rochester 2G 11/2” Flange 1 11/16 throttle bore

13/16 venturi 352CFM
11/4” venturi 381CFM
15/16" venturi 423CFM
13/8" venturi 435CFM

this is directly from the book Rochester Carburetors by HP Books

Carburetors are tested at a given pressure drop at WOT to obtain cfm rateing indicative to flow capacity. One- and two barrel carburetors are tested at 3.0-in.Hg pressure drop. Four barrel carburetors are tested at 1.5-in. Hg drop.

To compare the two rateings, use these equations:

Equlivlent flow CFM at 3.0 in. Hg
= -----------------
At 1.5 in. HG 1.414

Equilivelent flow
= CFM at 1.5 in. Hg x 1.414
At 3.0 in. Hg


So a 2G that is rated @ 278 would be the equilivelent to a 4 bbl that is rated @ 196.6

 

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Rochester 2G 11/4” flange 17/16” throttle bore
13/32” venturi 278 CFM




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Just to make sure I understand...
The flange is 2 3/4" ?
The throttle bore is 1 1/16" ?

Do you know what these carbs came on originally ?
Are they rare ? expensive ? Hard to find ?

 

No, the numbers are run together.
1 1/4 & 1 7/16 is the correct sizes. 1 3/32 venturi.
These carbs are the early ones that were used up to '64 IIRC. They are getting harder to find and more expensive at swap meets because they are the ones used on most after market tri-power setups. The side fuel inlet tops are getting very hard to find. '55 - '64 Chevy 2bbl motors will have them on it.
Mutt

 

Cool!
Thanks Mutt.
That means I have one already, does anybody want to sell me 5 more???