I just finished putting a fresh 350 in my chevelle, and I'm having some trouble getting the carb tuned. Its a Holley 750 (3310) that is supposed to have stock jets, etc. I have added an electric choke. When I floor it at any speed, it hesitates, and somtimes pops back through the carb, then goes. The floats are set with fuel to the bottom of the site holes, and I got the idle screws set to the highest idle vacumn (17" in park, 15" in gear). I have tried different accelerator cams, but havn't noticed a difference. I can't tell if it need more or less fuel. Could it be the power valve? It should have 6.5 in it stock. Do I need a 7.5 or 8.5? I've also thought of getting a different squirter, but I don't know it I need to go bigger or smaller. Any ideas would be a big help.

Heres some more info on my combo:
350 bored 40 over
World products sportsman II heads
Edelbrock performer EPS intake
Headman elite headers
TH350w/ 2800 stall converter

Thanks

popping back through the carb could be a timing issue.

Your accelerator pump is not working.

I was assuming the accelerator pump was the problem also, but when I changed pump cams I didn't get any difference. With the engine off I get a shot of fuel when I open the carb, but maybe its too much or too little. I tried looking at the Holley web sight and they say if it back fires its lean and you need a bigger pump and if it isn't running clean it needs a smaller pump. Its does pop out of the carb, but it almost seems like it gets too much fuel and has to clean out before it goes. So I'm not sure which way to go. This is my first Holley so I'm adjusting by what ever info I can find.

Look down the barrels and operate the throttle lever. You should with "VERY" little movement get a little quirt out of the quirter. If you don't and the pump is good you probable need to adjust the spring bolt combo on the accerator pump. If you do you probably need a larger quirter. Holley says I think go 3 sizes at a time till you get black smoke out the tail pipe then back off to the last size.
Hope this helps Good Luck

Had the same problem with my 3310.

http://www.camaros.net/forum/ultimatebb.php?ubb=get_topic;f=4;t=006236#000003

Read the advice given by Eric68. It solved my problem.

Thanks for the help. I will try to play with the accelerator pump some more. I looked at the link to the camero site and the ideas Eric68 gave. My only question is the power valve. I've read that you should take 1/2 of the manifold vac at idle, somewhere else said 2" lower than crusing speed, and he was saying 2" lower than idle. My vac at idle is 15" in gear, 1/2 would be 7.5. If I go 2" lower I have to go to the max size of 10.5. What's right?
Thanks again for the help.

What is your timing as thats what the issue sounds like to me. I run a 3310 right out of the box on my 454,with only a change in the secondary spring and a quick float adjustment.Works mint graemlins/thumbsup.gif
You might want to install all the factory spec's..like the stock jetting,powervalve,etc. and go from there..Eric's advice should more than help too.

The power valve should be 2" below idle in gear!

had the same problem and changing pump cams made very little diff. So I started changing the accell
pump discharge nozzles and when I went up a few sizes it fixed the problem

Originally posted by Steve1972:
Thanks for the help. I will try to play with the accelerator pump some more. I looked at the link to the camero site and the ideas Eric68 gave. My only question is the power valve. I've read that you should take 1/2 of the manifold vac at idle, somewhere else said 2" lower than crusing speed, and he was saying 2" lower than idle. My vac at idle is 15" in gear, 1/2 would be 7.5. If I go 2" lower I have to go to the max size of 10.5. What's right?
Thanks again for the help. Both recomendations are correct and from Holley's tech site. The thing is one is for a stock engine and the other is for a high performance modified engine making very little vacuum. The stock or mild performance engine making good idle vacuum should use the 1/2 the idle vacuum rule, that would equate to a 6.5 or 7.5 for an engine making 13 or more inches of vacuum. The 2 below idle vacuum is for the high performance low idle vacuum engine. These are guidlines and can be adjusted to help you tune your combo. You don't want the PV to open when the engine is idling or when you crack the idle a bit but you do want it to open when you go WOT.