Holley carb adjustment question:

[jjl4004]

I was wondering if anyone knows what the proper setting should be for an accelerator pump spring (I think that’s what it’s called). You can see what I’m talking about in this link. Page 10, figure 11. I’m talking about the spring/bolt/nut right above the word “screw” in the picture.

http://www.holley.com/data/Products/...99R10219-3.pdf

I’ve got a Holley Street Avenger 770cfm vacuum secondary carb on a 396, 60 over BBC with a somewhat mild cam with 10.4:1 compression. I mostly run it on the streets if that makes any difference. Any suggestions would be appreciated.

[robot]

Used to be that you adjusted the accelerator pump so that you had about 0.015" of lash when the throttle was wide open. You accomplished this by opening the throttle all the way and measuring the free play between the bolt head and the pump arm using a feeler gauge. To adjust, the bolt/nut were turned to make the bolt longer or shorter. This adjustment gave you full pump stroke without bottoming the pump out at full throttle. Of course, the approved adjustment may have changed due to daylight savings time, metric system, CE directives, or such.

By the way, changing the pump cam requires readjustment of the free play.

Mike in Tucson

[rgebbie]

does anyone know how to calculate the gear ratio versus cam, tire height, transmission?

Rich in Cleveland

[jjl4004]

Thanks guys, I'll go see where I'm at once I get home tonight...

[robot]

I might add that getting the right pump cam is the difficult part....each cam profile is identified by the color of the plastic. Each cam proflie tailors the timing and rate of the pump squirt.....shoot your whole shot quickly and early OR wait until later.....or slow and spread over the entire event.....your choice.

[robot]

And Denny's picture brings up another good point for those learning about squirts.....most of the cams have two holes, conveniently labeled "1" and "2" while some have 3 holes and some have only 1

The cam can be positioned so that the mounting screw goes into either hole; one hole advances the cam, one retards it. Just another tuning feature of a Holley.

[jjl4004]

Thanks for all of the info guys. Do you know what pump cam comes from the factory? Which one is best for a mostly street driven application? Are they difficult to change? I try to stay away from digging into carbs, as I don't know a lot about them. Thanks again...

[robot]

The cams change with only a screwdriver and perhaps 6 of your fingers....the pump adjustment is with two 3/8 winches (if my memory serves me correctly). I switched to fuel injection and forever swore off carbs unless it was for a future drag car.

Different carbs come fitted with different cams...depends upon the intended use. The cams are really cheap at you local go fast store

[NTFDAY]

Buy a book like this one, it's full of good info.

[jjl4004]

Thanks guys, I adjusted the accelerator spring and it's running great now. I appreciate the advice.