All I ran was a used off the shelf Holley 600.
My car is primarily a road race car but I make it out to an autocross once and a while.
What kind of problems are you having?

Greg

 

All my problems that I am having is in this thread: http://www.corral.net/forums/showthread.php?t=984386

Towards the end is where my current issues are. Basically I had put bigger jets in the carb then whats supposed to be in it stock because the stupid shop that tried tuning it put smaller jets in it then stock so I had a lean condition. So after the bigger jets it ran a bit rich but not terrible. So I dropped down my jets closer to stock, just one size bigger, 72/80, stock is 71/79, and now it runs even richer and I cant seem to lean it out. If I turn all four of the mixture screws in it does not seem to have an effect on how the engine runs. I recently put a new main power value in it but it might have got blown out monday night from a carb fire.

Shane

 

Rather than throwing $$$ at the problem, why not call BG? Give them your engine and car specs and get their reccomendation on set-up. At worst, find out what it would cost to send it to them and have them go through it and tune it to your combo.

 

Shane,

I would agree that a 600-650 is the right size for that motor. I have always had the best luck with mechanical secondaries, though a buddy swears by his vacuum ones to soften the power delivery a bit. He is an ex drag racer and is pretty good at tuning them, which is not something I am afflicted with.

I didn't read your other thread to see if the problems are constant or only on the autox course. To make a carb work on an autocross course, you need to do a few things:

1) You want center hung floats, period.

2) In the rear, use a circle track float and cut the other corner off to match. Jet extensions are optional.

3) The float level must be set VERY precisely. When you bump the car, just a slight drip over the edge. Forget the clear plugs, not accurate enough.

4) If the others are done, this probably isn't needed. Take a piece of fuel line and connect the front and rear bowl vents. CUt a slot in the top of the hose to allow them to vent, but make sure the slot doesn't seal shut with the air cleaner on. This will eliminate the problem of loading up under hard braking.

HTH,

DaveW

 

You say the engine is running rich. When? At idle? WOT? Cruising through the paddock?

I'm not sure how much experience you have tuning a Holley carb, and it is hard to diagnose via the internet, but it sounds like you have gotten the throttle plates out of whack.

I believe that what you are calling the mixture screws are actually the idle mixture screws. If adjusting them doesn't make a difference something is way wrong. If true, it sounds like you have uncovered the transfer slot which is designed for a smooth transition from idle to the main circuit. If the transfer slot has been uncovered, it draws fuel past the idle circuit and will make the idle screws ineffective. This happened by adjusting the throttle plate screw too far in therefore opening the throttle blade too far.

Get this book: http://www.amazon.com/Holly-Carbure...ook-4150-Hp473/dp/0895860473/ref=pd_bbs_2?ie=UTF8&s=books&qid=1201826919&sr=8-2

It may not be brand new, but it will describe the basics of how a carburetor works and the sequence of adjustments that need to be made to make it work.

On Edit: The jets only make a difference when the engine is running on the main circuit. Another issue could be a blown power valve. If the power valve is ruptured due to a backfire or just age, it will dump fuel at all points in the rpm range.

Second Edit (I'm working hard for you here): Here is a link to a super Cliff's Notes version of how to tune a carb. http://www.carcraft.com/howto/77958/index.html

 

I'm not sure how much experience you have tuning a Holley carb, and it is hard to diagnose via the internet, but it sounds like you have gotten the throttle plates out of whack.

I believe that what you are calling the mixture screws are actually the idle mixture screws. If adjusting them doesn't make a difference something is way wrong. If true, it sounds like you have uncovered the transfer slot which is designed for a smooth transition from idle to the main circuit. If the transfer slot has been uncovered, it draws fuel past the idle circuit and will make the idle screws ineffective. This happened by adjusting the throttle plate screw too far in therefore opening the throttle blade too far

Thats actually one of my big problems. Fuel pressure is the first thing thats wrong on my carb and second is that the throttle blades are open to much. I talked to a tech at Barry Grant the other night and got a lot of good advice from him. I'm going to tear the carb off my engine maybe tonight or tomorrow morning and set everything up how it should be and see how it runs.

Thanks for the help! I appreciate it a lot.

Shane