Holley optimum size for a 256 Merc.

B

Bruce Compton Canada

Senior Member
I have a Holley 1848 (465 cfm) carb and was wondering if I should be looking for a Holley 390 cfm instead. It's for a stock 1954 256" Merc with 3 speed overdrive ******. I already have the ECZ-B 1957 intake to install it on. Thanks : Bruce
 
The 390 may be better for the 256. Two things, you will need a 57 up distributor and ensure you get a good seal on the intake. The B manifold has much larger ports that the 256 manifold and may not seal properly to the 256 heads.

For sure you will have miss matched ports.

Just my 1¢ worth.
 
Thanks : Should I keep the stock 256 intake with a carb adaptor, put up with the mismatched ports of the later intake, or hog out the ports on the head to match the later intake (without removing the heads)?? I already have switched to the '57 up distributor. Bruce
 
Use the stock intake with an adapter,it's better to have the proper port alignment manifold to heads.Save the "B" intake for a future 292-312 build, the "B" intakes are getting pricey as of late $200+ on ebay and www.y-blocksforever.com
 
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