Helping a newbie with a dragster he just purchased. Steve Schmit motor, runs 4.69-4.70 last weekend.

It seems to stumble a bit when coming up from the SLE. I'm thinking it could use a bigger shot from the squirter, but don't know the sizes used on a typical 4500 Holley.

Any suggestions?

Balance the idle stops and mixture front to rear, especially if it's a 3-circuit unit. Might just want a touch more idle fuel or the "main" idle stop is past the intermediate feed. You adjust all 4-corners equal to get where you want.
Oh yeah, clean out the air bleeds first and see how it is.
Check to make sure the pump arms are adjusted correctly.
The squirter size is actually used to time the duration of the squirt.

Dave, thanks man, did most of that. Didn't check the air bleeds.

Could give it a touch more fuel on the mixture screws.

What size are the nozzles on the 4500?

Check out this link carb tech it has all the info you are asking about.

I'm thinking we had 37's, maybe came with 35's?

I can get away with 35's in a 1250 on mine, but some engines just need some fuel. Up to 45 on a gas 1250, 1050 42's. Any more than that and I would be looking for other problems, incorrect timing, plug heat range, plug wires with too much resistance, something bad in the ignition components. Make sure there is no slack in the pump arms at idle.

Don't forget to look at the pump cams. Not only are you trying to get the right amount of fuel shot, but you need to time the pump shot as well.

You mentioned "stumble". Does it feel like a lean stumble or is it blackish? If no black, I would go up by at least one nozzle size on the rear squirter.

I will add this:

For heavy combo's without rear gear to help and larger carb's and or intake plenums and relatively smaller cid's, you will need more fuel to cover the hole from smashing open the throttle vs light combo's all else being equal. In addition, the weather matters also! Great air conditions can cause and otherwise good running carb combo to stubble at the hit.

I have had 52's in 1250 to 1450 CFM carbs to get the stubble out. I am not a big fan of adding more fuel at idle either to crutch this problem if the idle mixture is good to start with, ie not lean!

If you are leaving off the transbrake then tear gear or weight of car should mean a thing because the throttle is wide open already when the brake releases.

THanks guys,

No it doesn't puff black. It just makes a little burb before jumping up to the two step.

He's using a SLE so it's right at the throttle opening. I'll twiddle with it a bit more this weekend. I'll look through my box of pieces for a bigger nozzle. Just wanted to know where to start.

The linkage looks good, added a bit of spring against the lever.

quote:

Originally posted by green1:
If you are leaving off the transbrake then tear gear or weight of car should mean a thing because the throttle is wide open already when the brake releases.

You are correct however T brake combo can be even worse than foot brake combos due to a starting line enhancer which slams the throttle open! So it still has to get to the chip cleanly!!! which it won't if its to lean... the bottom line is the accel pump shot of fuel has to fill the hole when the throttle is slammed open until the main circuit kicks in!