I've heard that the stock carb on the 239 Flathead isn't really that good, and more carburation is an easy hop up. How much more with a stock cam? What are the suggestions for a single bigger carb? A 2 carb setup? What does it do to the mileage? Should go down because you're shoveling more gas in?
>I've heard that the stock carb on the 239 Flathead isn't
>really that good, and more carburation is an easy hop up.
>How much more with a stock cam? What are the suggestions
>for a single bigger carb? A 2 carb setup? What does it do
>to the mileage? Should go down because you're shoveling
>more gas in?
Function-wise there's nothing wrong with the stock carb. Most rebuilds don't do a thorough job and forget to clean the smallest passages and emulsion tubes. They were made with dozens of mods and upgrades over the years.
More is better up to a point. First mod you do should be headers, then carbs, then cam. The original Holley 94 carbs are rated at 155 cfm, ECG models from the mid-50's are rated at 185 cfm. About the most a flathead V8 can handle is 390 cfm, so you have some practical options.
Get a new Holley 390 and try to find an original intake to fit, or make your own.
Get a two deuce intake from Offenhauser or Edelbrock and use 2 stock carbs. They really don't handle 3 very well even with smaller jets - just gets too much fuel and runs rich. The super duals, which spread the fuel more evenly to all cylinders require you to move the generator from the stock location - either sideways or replace with an alternator.
If you're running one of these who cares about mileage, right?!
Read thru the articles on this sight for more detailed info.
I'm running it on a dump truck that I use for actual work, so emissions and fuel mileage are a concern. With a stock cam can I utilize the 390 cfm? Are headers really that much of an improvement? The truck manifolds practically look like headers....
[updated:LAST EDITED ON 06-Dec-02 AT 05:18 PM (EST)]Hi,
Took me awhile to find this, but it should give you some ideas as to the performance upgrades in HP gains. According to this chart dual intake or 390 cfm carb is the place to start.
Glad to hear you run a working truck - my '48 pickup is a daily driver also. I'm running headers right now, but plan to add dual intake in the near future along with a mild cam. I had to swap this engine in (it was going to be my hotrod engine) when I found a crack in the original.