Rochester 4GC Carb - ClassicOldsmobile.com


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Old July 1st, 2018, 10:45 PM   #1  
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Rochester 4GC Carb

Was looking at my 394 today that I have sitting, the carb is different that is forsure.

Pros/cons to these carbs?
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Old July 2nd, 2018, 09:16 AM   #2  
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They are great carbs if they are properly built with good parts. Not being in production since the 60s may make parts hard to find but definitely possible. If you are dealing with a car equipped with the Slim Jim trans they are the only carbs with the proper linkage to hook up.
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Old July 2nd, 2018, 11:14 AM   #3  
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Square bore vs. spread bore = no interchange with later Q-Jet, if that's what you're thinking.
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Old July 2nd, 2018, 04:02 PM   #4  
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Just curious. I have intentions of building a 394 one day like all other potential projects I have.
Put it in a late 30's or early 40's olds.
Cool looking carb, kinda aiming to keep the 394 old school looking.
I know nothing about Slim Jim trans, kinda kicking the idea of a standard with the 394.
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Old July 2nd, 2018, 05:10 PM   #5  
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Quote:
Originally Posted by Kyle's77cutlass View Post
Just curious. I have intentions of building a 394 one day like all other potential projects I have.
Put it in a late 30's or early 40's olds.
Cool looking carb, kinda aiming to keep the 394 old school looking.
I know nothing about Slim Jim trans, kinda kicking the idea of a standard with the 394.
Slim-Jim is the nickname for the Roto-Hydramatic automatic transmission. Most people stick with them in the early 60s B-bodies they came in due to clearance issues with other transmissions, but if you're planning on building an old-school hotrod there's no reason to use one. You'll end up doing plenty of fabbing anyway.
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Old July 3rd, 2018, 08:48 AM   #6  
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Okay good to know.Thanks
From the island I see, hows it out there?
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Old July 3rd, 2018, 09:40 AM   #7  
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Okay good to know.Thanks
From the island I see, hows it out there?
Good. Great weather today!


Where you at?
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Old July 4th, 2018, 01:51 PM   #8  
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Quote:
Originally Posted by Kyle's77cutlass View Post
Just curious. I have intentions of building a 394 one day like all other potential projects I have.
Put it in a late 30's or early 40's olds.
Cool looking carb, kinda aiming to keep the 394 old school looking.
I know nothing about Slim Jim trans, kinda kicking the idea of a standard with the 394.
Most folk are not aware that "back in the day" one could get a factory 3-on-the-tree behind the 394. How do I know? I was lucky enough to own one and it hauled you know what! Mine was a 1960 Super 88 Holiday SceniCoupe (bubbletop).

Last edited by D. Yaros; August 13th, 2018 at 02:47 PM.
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Old July 4th, 2018, 04:37 PM   #9  
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Oh I bet. I read up on the 394, was a power house back in the day. 345hp and 400 ft lbs torque.
Hard to keep rubber on them rims. Lol
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Old July 5th, 2018, 11:21 AM   #10  
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Here is a place that I've bought 4gc parts from, there are others if you look a round. They are not a bad carb if not to worn out..... Tedd....https://quadrajetparts.com/accelerat...c-104_109.html
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Old July 5th, 2018, 11:45 AM   #11  
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Sweet. Thanks
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Old August 9th, 2018, 11:07 PM   #12  
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My Q-Jet packed it in.
I just so happened to have a brand new Holley 600 Vac secondary in a box in the shed.
Had to get an adaptor plate as the manifold bolts do not line up with the Holley holes. Drives beutifull ever since.

You can also use a 600 Edelbrock, apparently bolts straight on, or I think you might need an adaptor plate to go to square bore.
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Old August 10th, 2018, 12:47 PM   #13  
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4GC are either good or junk in my experience. Very sensitive to having the right throttle plate to bowl gasket. They have primary and secondary side floats and the secondary air valves are buried deep in the carb. Kinda small in CFM department too, 450-500 IIRC. But set up right they will boogie with the rest of same or near CFM rating.

Any chance this one still has its aluminum ID tag under an airhorn screw? Makes it ever so much easier to get the right rebuild kit.
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Old August 11th, 2018, 09:10 PM   #14  
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4GC are either good or junk in my experience. Very sensitive to having the right throttle plate to bowl gasket. They have primary and secondary side floats and the secondary air valves are buried deep in the carb. Kinda small in CFM department too, 450-500 IIRC. But set up right they will boogie with the rest of same or near CFM rating.

Any chance this one still has its aluminum ID tag under an airhorn screw? Makes it ever so much easier to get the right rebuild kit.
Yes, both have them on
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