There is a very good book out there called "Tuning Holley Carburetors". It does a good job of breaking down the different fuel circuits and how to tune them. It gives you enough information to be able to go out and tune just about any carb as the theories are all the same. I would highly recommend buying it as I still reference mine from time to time. I have a mild 460 in my 77 F250 with an Edelbrock 600, and it runs great, starts right up in the winter with no choke. I have been thinking about putting a 750 on because the engine is not totally stock and has potential for moving more air through it. I read a lot on this forum that a 750 would be too big but I may still try it. I have always ran Holleys in the past but I'm finding this Edel is pretty easy to tune. I found a place on Ebay Motors that sells remanned Edel carbs for $200 with a lifetime warranty so I may throw a 750 on and try it.

 

750 if it has vacuum seconderies Manual if u plan to run roundtrack !!! LOL

 

For billg302,

I was amazed at the difference when I went from the 600 to the 750 Edelbrock. My 460 has a stock cam and with the addition of the head work, roller rockers, straight up timing, MSD ignition and 2 ½ “ exhausts into Flowmasters is pretty much stock. I hope you have the same improvement in yours as I did in mine.

 

Engine Displacement (ci) x max rpm / 3456 = cfm

that'll tell you the max cfm's running at 100% volumetric efficiency at redline (the biggest carb the engine SHOULD have

here's my 351 for example

351 x 5500 / 3456 = 558.59 cfm

 

well im gonna go change the accelerator pump then. i noticed the 750 at over 25oo rpm is better i can hear it out the exhaust but the 600 was better idle to about 2k rpm. if it is as simple as that i will be happy. but i have to get on it going to the mountains today for the weekend. scouting trip for the trucks. this is a quad weekend. still fun though less seems to get broken. thanks for all your help everyone.

 

I have a 69 pre smog 460 in my 77 F250 4x4, C6, 4:10s, and run a Holley 600 on it (what we called the super shops special) and it runs out really well. I had a Holley 750 dominator on it for a week or so I could rebuild the 600 and the 750 seemed like way to much carb. I get around 14 mpg in it with the 600, no hesitation at all and you can take off and get rolling about 20 mph or so and jump in it and it will light up the rear tires with little effort. I have watched my kid do it when he thought I had went into the house.

 

The lowest hole will give you the biggest (longest) shot, the highest hole the smallest (shortest) shot, the middle hole obviously a compromise between the two.

 

wb6vvv, I will give a 750 a try, I have seen a few guys with 460's have good luck with them. I forgot to mention mine has an RV cam in it, not sure what the specs are on it. Where do you run your initial timing? Thanks for the input.

 

The Race Demon carbs actually flow higher than their listed rating. The 750CFM on my Mustang flows closer to 800 cfm.

If, during tests, you discover that the motor wants 2 or 3 jet sizes larger in the carb, then the carb is likely on the small side for the motor, which is a good thing, especially in a heavy vehicle. If the motor wants 2 or 3 jet sizes smaller, then the carb is likely on the large side. Throttle response won't be as crisp, and you may sacrifice low end torque with a slightly over-sized carb. If you need to change jets more than 3 sizes up or down, the carb is wrong for the motor. It will certainly run anyway, but efficiency will suffer.

As for the off-idle response; You can adjust the accelerator pump arm and often get rid of any hesitation. Once the pump is full of fuel, adjust the arm so that you can wiggle it with your fingers and there's a very tiny amount of slack between the arm and the pump base. Probably as much of a gap as a sheet of paper or less. If there's too much play, the acc. pump won't spray fuel quick enough, and if the arm is too tight, the acc. pump won't spray enough fuel for the task. You can change the acc. pump nozzle to a different size, and you can also swap out the plastic pump cam if necessary, too. If you ever find yourself needing to make your own acc. pump cam, I've found that a plastic windshield ice scraper handle makes the perfect material for such a thing.

 

I have the variable timing MSD ignition with the pot on the dash. That way you can vary the timing for driving conditions. I have it set so that the timing will be at 10 degrees with the pot at minimum and 19 degrees with the pot at maximum. I normally drive at about 14 degrees.

 

That's pretty cool, I've had lots of MSD stuff, but never tried that variable timing setup. Does it plug in between the distributor and box?

 

The MSD Unit comes with its own module. You just unplug the DuraSpark module and plug in the MSD Module. The unit just directly plugs in using the standard Ford type plugs. No mods are needed. You run the leads to the potentiometer inside of the cab and secure the pot to your dash. You turn the pot fully counter-clockwise and set your static timing to 10 degrees. That's it, it is installed. The next step is to move the pot up to where you want to run your timing and note the numbered position on the dial. That way you will know where you want to set it back to if you have to move it for different driving conditions.

 

thats correct..........but in reality you should take the final number and multiply it by about .7 or .8 This is due to the fact that short of some sort of forced induction the most efficiency you will get is about 70-80%. The best naturally aspirated race engines are about 90-93% efficient.

It is better to be a touch to the small side than too big when it comes to carbs.




(technically speaking of course)

 

Some race engines exceed 100% volumetric efficiency.

 

If you are going to run a vacuum 2nd 750 Holley get down leg boosters put in if it doesn't already have them. They make a big difference in a big heavy truck. Some say they are restrictive, but even if that is true the benifit far outweighs it.