New carburator 350CFM vs 500CFM?

[jagarra]

Been thinking about upgrading the carburetor on my truck. I have heard about the 500 CFM Holley being used, has anyone tried the 350 CFM model or is it not enough flow??? Anyone tried it out there?

[bigblockv6]

Don't waste your money on the 350cfm version, it doesn't make any difference from the stock carb. I've experimented with both the 350 and 500 cfm carb, the 500cfm will give a dramatic increase in performance and driveability.

[jagarra]

Thanks, just the information I was looking for.
My stocker is working, but I am not happy with the way it works. Fuel usage isn't great, about 9 mpg in town and best I have recorded is 11 on the highway. It just feels funny through the gas pedal, not working smoothly throughout the range. I do have another kit for it, I guess I will try that first since I already paid for it. Rebuilt a few months back, but I had to use the old accelerator pump piece.
What is selling me on the Holley is that it is jet-able, I have a Summit retail warehouse/store in the area, so it is no problem getting different jets to tune it.

[bigblockv6]

On the Holley you don't have to take off or pull the whole carburetor apart, just the front bowl when re-jetting.

[jagarra]

When I was looking at carbs, I see a 4412S and a 4412C, both look like the have manual chokes, any major difference?/

[bigblockv6]

One has the cadium plating that looks chrome, that's the difference.

[jagarra]

Thanks for all the information Big Block. Ordered one of them 4412 C as I don't like the looks of the shiny one as much.
Are there any issues hooking up the fuel lines and vacuum line for the distributor like thread pitch. Reason I asked, when I was looking at the Summit site, when you brought these Holleys up they listed some fittings like an AN6 with an inverted flare as something folks bought at the same time.

thanks again,

[Clyde]

I installed a 44121C on my 1966 GMC 3/4T PU,351 V6, I made the adapter for it. I also installed an HEI from an Buick V6. I had to lean out the carb a little. The GMC has 4.10 rear, AT400 and a gear vendor OD which drops the RPM's 500, I average a little over 12 MPG mixed driving. The engine starts much better and runs better, great up grade. I have to thank the fellows before me on this forum for the information. You will not disappointed in the Holley 500.

[aphaynes]

Isn't there an adapter plate needed for the 305 as well to go with the 500cfm? Is it available on line or do you have to make one as Clyde did?

[bigblockv6]

The adapter is available from more than one manufacturer, the most common everyone uses is the Mr. Gasket #1937 adapter, TransDapt also makes one.