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tubman · 09-26-2018, 07:25 AM

Now that you mention the Holley 390 CFM unit, here are some numbers to think about : a Holley 94 flows about 140 CFM, while a small base Rochester flows around 280 CFM. You have to be careful comparing 2 BBL vs 4 BBL flow numbers because they are rated differently. The 94 and Rochester are both 2 BBLs, so I think you can do some meaningful comparisons.

I have a 255 '51 Merc with Edmunds heads, a Mallory dual point, and a small base 2GV in my '51 Ford club coupe. It starts easily, runs well, gets decent gas mileage (19 mpg on a 250 mile road trip at 65 on the interstate), and performs excellently overall. Since I use this car as my daily driver during the summer, I really appreciate not having to fool around with a dual carb setup. (It doesn't look nearly as impressive, though.)

The hardest part of installing one is preparing the manifold (although the carb does just bolt on). I'll agree with Sal about rebuilding the original if you are into stock restorations, but for a flathead powered DD, you will find a 2G hard to beat.

09-26-2018, 07:25 AM	#7
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 11,639	Re: Carburator Mercury 255 Flathead Now that you mention the Holley 390 CFM unit, here are some numbers to think about : a Holley 94 flows about 140 CFM, while a small base Rochester flows around 280 CFM. You have to be careful comparing 2 BBL vs 4 BBL flow numbers because they are rated differently. The 94 and Rochester are both 2 BBLs, so I think you can do some meaningful comparisons. I have a 255 '51 Merc with Edmunds heads, a Mallory dual point, and a small base 2GV in my '51 Ford club coupe. It starts easily, runs well, gets decent gas mileage (19 mpg on a 250 mile road trip at 65 on the interstate), and performs excellently overall. Since I use this car as my daily driver during the summer, I really appreciate not having to fool around with a dual carb setup. (It doesn't look nearly as impressive, though.) The hardest part of installing one is preparing the manifold (although the carb does just bolt on). I'll agree with Sal about rebuilding the original if you are into stock restorations, but for a flathead powered DD, you will find a 2G hard to beat.