351M Carb dilema

77 Ford LTD with 351M, stock except for exhaust and a 327 posi rear end. hopefully someone can help settle a debate between me and my buddy mechanic.

600 or 670?

Wanting to keep fuel economy as good as possible, I think the 600 is best and when I do the math, the motor does not need anymore than a 600.

He is recommending a 670 saying it will not have any adverse affect on fuel economy unless I stomp it because the primaries are the same size. He swears that the 670 is not too big. Now that my gear ratio has changed I am at much higher RPM's at highway speeds, so the 670 will make sure I have all the juice I will need.

My choice is the edelbrock 1406 600 CFM. His suggestion is the Holley 670 street avenger. I know the difference in price is impacting my decision,

Any feedback or suggestions would be awesome.

Thanks


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I alway's ran the 780 Holley or the Holley 3310 750 vac sec on my Cleveland's.
I did the same on my 351 m in my 79 f150 4x4, but IMHO either one would be fine the 600 or the 670 just a street cruiser right ? My personal preference is with the Holley i'm just not a big fan of the edelbrock carbs but aloy of guy's do really like them though. JMO



Cole

Thanks for the reply

I have always had Chevy's in the past and used edelbrock, so I don't have much experience with Holley. I have read a few posts from ford guys saying that the Edelbrock kick down linkage does not work well, but no complaints with holley.

I am only getting 12 MPG, so I am nervous about the impact of the 670 over the 600. Will there be a noticeable difference in fuel economy if I restrain my foot?