440 issues

[jahlg]

Ok ill try again, 440, 4 speed. Starts right up, idols fine, pulling 12 in vacuum, when you ease into the gas it starts to hesitate, if you put it to the floor it runs good, not great but doesnt stumble, have already adjusted carb, which was swapped from Edelbrock, to Demon, changed plugs, and adjusted timing, and swapped msd 6 box. Help!!!

[ehostler]

What did you do to adjust the carb?

Too me, it sounds as if the accelerator pump is mis-adjusted or the wrong size.

[John Kunkel]

An off-idle stumble is most often caused by a lean idle condition, running the mixture screws on the rich side will often cure the stumble.

[jahlg]

The problem carried over from one carb to the next, and it was running very rich, as far as what was adjusted, i am not sure, my buddy did that, and i trust him, hes been tuning cars his whole life! So i am not thinking it is a carb problem if it didnt go away by swapping carbs.

[JVMopar]

I have to agree try adjusting the accelerator pump to squirt sooner.

[crisser]

Originally Posted by jahlg

my buddy did that, and i trust him, hes been tuning cars his whole life!

Then, he should be able to diagnose your problem?
"When you ease on the gas". Is this in neutral or under a load?
Sounds like there might be some slack in the accel. pump arm/lever on tip in.
A Demon carb. should have a way to adjust. But, iv`e not worked on Demon carbs. and can`t see it on the computer.
The other guys on this board that are trying to help are not there either. Kinda hard to troubleshoot over the computer without sights, sounds, smells, etc.

[ehostler]

Unless your buddy did more than just adjust the idle jets, he didn't do much. The simple adjustments are idle jets, accelerator pump, and the idle EZ circuit (on the Demon). Beyond that require opening the carb and replacing jets.

Going from a wrong size carb to a wrong size carb will also maintain problems.

Now for my big question. If you trust your buddy as he has been tuning cars his whole life, why isn't the problem fixed and why are you here asking for help that you refuse to accept?

[RAM MAN]

what did you find out ?

[cudabob496]

Is the 12 inch vacuum while in gear, or in park?
Could be timing curve.
I had a similar problem and the primary jets were too small.
Or accelerator pump problem.

[jahlg]

First, I never said i was refusing to accept the help, second he did adjust the accelerator pump, third he is just as stumped on this issue, we tuned on that hting for hours, got some results but didnt fix issue. Third, the vacuum was fine in gear and in neutral, we hooked up a vacuum gauge and took it for a spin as well, the problem happens whether i am driving or just sitting in the driveway. I appreciate everyones input, I dont really appreciate the attitude from the moderator though, a little uncalled for.

[rusty duster]

what is the vacuum at the port where the dist. is hooked to at idle?What is the timing at 3000 rpm? Do you have one of the new demons that have the idle air adjustment under the air cleaner stud?

[jahlg]

Distributor is not hooked to vacuum anywhere. Timing i believe was around 36 deg. The demon is about 6 years old, maybe a little newer, its a loaner from another friend. I dont know if it has the adjustment,

[crisser]

Select your carb series from the pull down list. Then, see if the carb is set up to it`s stock specs. If it isn`t, get it there and start tuning from there.

http://www.barrygrant.com/demon/default.aspx?page=29

[lazarus]

What's the initial timing set at and at what rpm is total timing all in?

[MOPEkid]

What about air leaks? My old Carter BBD had worn throttle shafts causing a big vacuum leak and no matter what I did it would always stumble when stepping on the gas. Obviously your carb is much better than mine was but you might have a vacuum leak somewhere else (carb-to-intake, intake vacuum ports, intake-to-head seal, etc.).

[chirorod]

lots of possibilities. check accelerator pump squirt. should be good and strong. might need new accelerator pump. timing might need more advance. what is timing at idle? if distributor vacuum is ported, try non-ported. can set timing by ear method. keep advancing timing until it just barely pings under full load, then back off a couple degrees. also, do basics. check compression. is cam ok? do thorough vacuum leak test. stick with it. there is always an answer.

[jahlg]

I have not given up hope, there is a local garage that is known for its work on classics, i am going to take it there in the spring, cant afford to do it right now, so she is going to sit idle for the winter, i am gonna rebuild my Holley double pumper, and upgrade to the MSD distributor and wires over the winter.

[pcrmike]

Cool. Betcha still find an issue with the squirt. Accel pump issues are the most common causes of this malady. Likely was teh issue with the Eddy you took off too. Out of the box they are usually a little lean on the accel squirt for a modded engine. Good luck and let us know. :-) PCRmike