Cfm for Hudson 308 engine

I have been looking through everything online and coming up with not a lot. Several of said that the Holly double pumper 600 CFM carburetor would work ideal on a Hudson engine. Is this correct?

I would like some more input on the correct CFM carburetor for my engine. I'm building the 7X and I have the new aluminum hornet Superdome head.

Thanks for all input on this matter. I have a jack Clifford intake and Jack Clifford headers that are going on my engine. Let me know what would be the best CFM for this engine I'm playing with.

Thanks Wookie


  • 50C8DAN
    50C8DAN Senior Contributor

    Here is a copy of the Offenhauser chart that gives you what you need to know. The max RPM and engine size are what you need to look at. Do you realize the Clifford manifold is not optimized for good flow for an inline engine? The Hudson original Twin H was a much better design with very close equal-length runners, etc.

  • This may be true but at this time I can't afford the new style intake being designed. I need to put away 7,000 for hay this year

  • ratlee2
    ratlee2 Expert Adviser
    edited January 8

    An Autolite 4100 with a 1.08 venturi from a Mustang would be appropriate, but they are getting expensive now. A better alternatve would probably summit 500cfm M2008 series carb. A 600 cfm may not give you enough air velocity through the carb to give you a smooth idle.

  • 50C8DAN
    50C8DAN Senior Contributor

    For a 4 bbl application for something that is less than 350 cu in, especially a 6 cylinder, I would stick with the newer Edelbrock 500 AVS2. This gives you the best atomization in a carb due to the annular flow in the primaries. For street use a 600 cfm Holley double pumper with mechanical secondaries is way too much carb on a Hudson 6 and actually for most small block V8s unless they are heavily modified.

  • I won't put an Edelbrock carburetor on anything even with a million dollar bet. I've had my fill of one that did not work on an engine. I will put a 500 CFM Holly on the car. Thanks for all the input on the correct CFM for my engine.

    My carburetor will have to be set up for 5,000 ft. Edelbrock cannot be set up correctly and I spent two weeks on the phone with them just to get an approximation for the correct Jets springs and metering rods for 5,000 ft.

    I had great success with demon on the correct Jets for 5,000 FT elevation.

  • I’ve been using an Edelbrock 500 cfm with electric choke on a beyond 7x in my wife’s 40, since 1999. I’m real happy with it. I put a divider in my Clifford intake, to separate the front and rear of the manifold in an effort to keep velocity up. My carb is mounted sideways, with a single primary and secondary feeding each end of the engine.

  • At what elevation do you live at? I'm at 5300 above sea level.

  • I'm at about 1200 ft. now. I lived at 4000 ft and commuted down to 1200 for five years with this setup, before I moved down here.

  • 50C8DAN
    50C8DAN Senior Contributor

    This is one of the best carb guys on youtube and covers the issue of altitude and tuning very well. I am planning to put AFR gauges on both my Studebaker Hawk and Hornet as I move to different carbs. I am going from an older 625 cfm AFB on my Stude to an Edelbrock 500 AVS2 (modernized AFB) - a better size for the engine. The Hornet will be using the new Twin H2 intake with 2, 2bbl Webers, and that will take some tuning that is not found anywhere. An AFR gauge will be a major help in tuning. As far as a carb size, 600 cfm on any Hudson 6 is too big, unless you have a wild cam and high compression head, plus going for WOT runs. Will it run, sure, but you will probably not be able to tune it to get where you want it to be for regular cruising, regardless of altitude.

  • I've decided to go with the Weber two barrel on my engine. Everything I've read about it shows that it has good atomization on a 6 cylinder engine.

  • I'm looking forward to hearing how it works.