Rochester 4jet 4GC capability

67Nova421 · 07-23-2025, 01:14 AM

I know some of you probably run a Rochester 4jet or 4GC carb in certain classes. I'm wondering if this carb is capable of making some decent power? It's small...I know that. I have my doubts about it being able to support a 400ci SBC to 5500+rpm. I've heard they can make some power I just want to hear some real world experience and the draw backs of them. Thanks.

Woodfin · 07-23-2025, 07:29 AM

The small carbs run surprisingly well on a 283 or 327, especially to the 1/8 mark. But they are limited, and the same engine with a larger carb makes more power. A 400 would be greatly restricted.

Mark Yacavone · 07-23-2025, 06:14 PM

There are at least four different size 4GCs.
What are you working on?

67Nova421 · 07-23-2025, 10:02 PM

Quote:

Originally Posted by Mark Yacavone

There are at least four different size 4GCs.
What are you working on?

It's original off a 59 Vette. The primaries and secondaries are the same size so I'm thinking it's the smallest version? The reason I ask is I was trying to build an engine for the Vette that looked completely original and stock but it'll be a hopped up 400ci. 10:1 compression, ported 2.02 041X heads, 230ish cam @ .050. The 400 will probably make peak power about 5500rpm so if the carb can even get close to that I'd be happy. But if it's going to stall out at 4500rpm that's probably not going to be worth trying out.

I just finished a full rebuild lastnight

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And here's a pic of the primaries and secondaries if that helps determine which carb it is

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Mark Yacavone · 07-23-2025, 10:28 PM

The 59 is the smallest.
The 65/66 PP is a bit bigger.
What you want is a 340 hp 409 carb.
I don't think they had the filter up top , but that top you have will fit right on it. ;-)

67Nova421 · 07-23-2025, 10:57 PM

Quote:

Originally Posted by Mark Yacavone

The 59 is the smallest.
The 65/66 PP is a bit bigger.
What you want is a 340 hp 409 carb.
I don't think they had the filter up top , but that top you have will fit right on it. ;-)

Ok that's what I was afraid of. I have a nice 750 double pumper and a Victor JR I can paint the engine color and somewhat hide it all with a factory Corvette air cleaner. Is there a certain name for the 340hp 409 carb to search for it?

Dwight Southerland · 07-24-2025, 11:26 AM

Quote:

Originally Posted by Mark Yacavone

What you want is a 340 hp 409 carb.
I don't think they had the filter up top , but that top you have will fit right on it. ;-)

Or a 63-65 Oldsmobile 394 carb or 63-65 Cadillac 390 carb

07-23-2025, 01:14 AM	#1
67Nova421 Junior Member Join Date: Jul 2025 Location: Denver, CO Posts: 6 Likes: 2 Liked 1 Time in 1 Post	Rochester 4jet 4GC capability I know some of you probably run a Rochester 4jet or 4GC carb in certain classes. I'm wondering if this carb is capable of making some decent power? It's small...I know that. I have my doubts about it being able to support a 400ci SBC to 5500+rpm. I've heard they can make some power I just want to hear some real world experience and the draw backs of them. Thanks.

07-23-2025, 07:29 AM	#2
Woodfin Senior Member Join Date: Sep 2006 Location: Kilgore TX Posts: 536 Likes: 8 Liked 274 Times in 105 Posts	Re: Rochester 4jet 4GC capability The small carbs run surprisingly well on a 283 or 327, especially to the 1/8 mark. But they are limited, and the same engine with a larger carb makes more power. A 400 would be greatly restricted.

07-23-2025, 06:14 PM	#3
Mark Yacavone Veteran Member Join Date: Mar 2002 Location: Miles From Nowhere Posts: 7,815 Likes: 2,903 Liked 5,121 Times in 1,952 Posts	Re: Rochester 4jet 4GC capability There are at least four different size 4GCs. What are you working on? __________________ "We are lucky we don't get as much Government as we pay for." Will Rogers

07-23-2025, 10:28 PM	#5
Mark Yacavone Veteran Member Join Date: Mar 2002 Location: Miles From Nowhere Posts: 7,815 Likes: 2,903 Liked 5,121 Times in 1,952 Posts	Re: Rochester 4jet 4GC capability The 59 is the smallest. The 65/66 PP is a bit bigger. What you want is a 340 hp 409 carb. I don't think they had the filter up top , but that top you have will fit right on it. ;-) __________________ "We are lucky we don't get as much Government as we pay for." Will Rogers