My problem is that when I hit the accelerator, about midway, the carb sometimes sputters. Its like a backfire, but not quite. It just sounds like its almost coughing or something. Its been doing this ever since I put the carb on out of the box. I have a holley 670 street avenger, and even after all the changes I've made its still doing it. Here is what I've changed:
primary jets were 65 now 69
secondary jets were 68 now 70
squirter was 31 now 35
cam was orange now blue in #2 hole
I've got a vacuum reading of 20" and I have my initial timing at 10 with the crane vacuum can locked out at 15. Also hooked the vacuum up to full manifold. I have the hardest springs on my distributor wieghts (800-3200). Don't think this matters but I've already checked for vacuum leaks. I've also adjusted my floats 1/8" below sight plugs, fuel pressure is 6-8 psi. I just need some suggestions, anything would help.

 

Checked out a couple of things, the vacuum is 16" when the engine is in gear and the timing is around 16 btdc. I also checked my plugs and they were clean on the insulator which suggests its running lean. I'm going to up the primary to 70 and see what happens. I really don't understand why the engine still wants more. I've heard more than one person say if you're over 4 then its something else, but what? Also what is the best way to set the secondary jets?

 

Another update, I upped the main jet size to 70 and it still sputters. I just checked my plugs and it seems that its turning a bit brown now. Not a lot but a little, I think tha the main jet size is good but the secondary is still a little lean. I'm not sure how to judge if the secondary is right or not. I also think that my squirter size is a little large, maybe go down to 31 because before it had faster throttle response now it seems to have slowed some. Any suggestions?

 

i am not sure either. but when you find out what the problem is post it. I have a 4160 that is being a pain. Only mine is more of a problem of it sputtering from idle to 2000 rpm and then running just fine...

 

I ain't chickenman, but I'll take a shot anyway.

Try lighter advance springs.

Follow the instructions on the Holley website tech section on the power enrichment circuit. You have a mild street engine, so you need to determine your cruise vacuum. Get a power valve according to the instructions for the cruise vacuum you observe.

(When you ask for a specific person in the topicline, you limit potential responses. If you want the opinion of a specific person, PM them.)

 

Right now I don't have the capability to take the vacuum reading while cruising. The best that I could do was see what the vacuum would be at idle (in gear) and it is a high 16". The carb comes stock with a 65 power valve, was considering on going to the 85 and see what happens. So far my main jets are about right and I wanted to go down on pump shot to experiment. Another thing that is puzzling me is why my advance at idle (in gear) is around 16. According to some of chickenman's posts it should be 29-31 when you're using full manifold vacuum. I installed the crane vacuum can and I'm thinking about going back to the summit one that came with the distributor and see if it changes. I would change the springs but if I do then the mechanical starts to dip in at idle. Right now the range is (800-3200). I'll keep in mind the posting advice, my bad

 

You'd be doing yourself a huge favor if you'd buy a vac ga.
Tuning a carb or a distributor without one is practically futile. When it comes to tuning, you're better off without a tach than a vacuum ga. And they're inexpensive and easy to install.
NOBODY gets their carb/advance curve dialed in without one.

 

What I have right now is just one you hook up to the manifold, but to get a reading while I'm driving I would have to have it on the hood I'll look into getting one. Also I tried the other vacuum can and my advance at idle was even worse than the crane one. So I put the crane one back on, took off the lock out cam and only turned it out one turn from the lightest setting. Drove around and didn't hear any spark knock so I guess its good. Not sure about the sputter yet, I floored it once since the change and it didn't sputter, but the sputter only happened sometimes before too. I think I'm going to go down a squirter size to experiment. It may run a little better because the jet size is much larger than when the car needed the larger squirter.

 

Make sure you try and PM Chickenman, he is really cool and helped me out a lot. Although I haven't seen him on much lately (he was trying to sell his thirdgen, so maybe he did), but it is still worth a try. If I were you, I'd try and find out some more about what is happening. As suggested a vacuum gauge is a good idea. I just installed a permanent one below my A/C vent. Perhaps more useful would be an Air/Fuel gauge (wideband of course is better but at ~$500 for a setup that probably isn't practical) so you can see just what it is. It is real easy to think it is a stumble from being lean while it is in reality rich. Also I don't remember seeing you mention condition of the other ignition components. Wires, cap/rotor, coil, etc. Those things can make some mysterious problems. Also a handy tool is a mightyvac to check your vacuum advance can, and other things (like PVs). Just throwing out some more things to try.

Good luck

 

I just ordered a dual a pillar gauge set from summit. Got the vacuum gauge and another temp gauge because the one in my dash is messed up. Was thinking of the a/f gauge but I can use the plugs and see that. The plugs right now are a little tan so I think the jets are about right. I'm thinking that maybe the power valve is coming in too late and its making a lean condition when its cooler outside. It seems like it runs alright when its completely warmed up and been I've been driving it for a while. So far since I changed the vacuum can back over with my current settings it hasn't done it. Still wondering how to jet the secondaries though, should I just jet them and see if it goes faster or is there a practical method for doing this? I appreciate the help from you guys. Gives me some more things to look at. And by the way, I checked out my wires and ignition components and everything looks like its good condition. I still haven't switched up the shooter yet but I'll do that today and post the results. I also pm'd chickenman but haven't got a response yet. Thanks again

 

Just checked at jegs to see how much a wideband is. They have AEM wideband for 377.99 (jegs p/n 017-30-4111). A little less than whats been put out but its still expensive compared to the other units. I almost forgot to ask about this, I noticed today that my squirter is shooting gas at the venturing. The stream is actually hitting the venturi and running down into the throttle body, is this normal? If it isn't then how do I fix it?

 

I'm going to start another thread due the advice of five7kid. It'll have same title minus chickenman so I can get some more advice. Have some pics I'll post on it as well of my wieghts, have some questions there.