ready to give up..440 just won't run right.. HELP

[44070dart]

my engine is new ..440...set timing at 10* total 35*...new plugs/wires /coil/cap (checked double checked all) ....checked firing order 10 times .....adjusted Holley with vacuum gauge 15hg vacuum ..set idle & mixture .. 7/8 lbs fuel pressure..floats adjusted properly.. power valve fine ..car will rev fine in neutral ..no break ups sound great ...take it out and the moment you half way accelerate the car breaks up ...accelerate slowly or drive at sustained speed and it fine ..remove the vacuum advance ..plug line the same result... have a garage in the area that runs a Mopar at local track ready to give up and admit defeat :disgust: not just the money I'm so aggravated I can't find the problem ...(its the money too.. I could use it for some other parts)... ALL ideas welcome :icon_eyes:

 

[black64]

Any chance of a loose connection when you accel it moves enough to cause low or intermittent voltage to ignition? Maybe a loose ground or power wire?

 

[krowbar]

Accelerator pump diaphragm shot or wrong acc pump cam setting?

 

[pro-streeter]

I agree with the pump shot adjustment. Is the car an automatic? if so you should have a vacuum secondary Holley not a double pump. Stick cars can run doulbe pump holley vacuum secodary with autos. What size carb are you running, and have you checked the plugs for jetting yet? Don't get discouraged just walk away. My car took quite a bit of tunning to get it right. Now it runs out smooth rarly stumbles. I have a 750 double pump 383 4 speed RR. I am about 2200 feet elevation and run 72 jets primary and 74 secondary 65 power valve summer weather 90 plus degrees. Your vacuum is good almost too good mine is about 8. The cam must be very mild. Lots of items to consider just takes some research and time so hang in there.

 

[Garys1969RR]

Is this a steady load problem? Does it run at wide open throttle? Or does it completely die out. Or is this a problem that just occurs when you are changing throttle opening positions?

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If it breaks up worse as the throttle opens more, then may be an ignition problem such as weak spark. A more highly compressed mixture requires more voltage at the spark plug before the spark will jump the gap.

 

[44070dart]

I'll recheck connections ...acc.pump responds as it should used feeler gauge to set it..good squirt..automatic/ vacuum sec. 750 carb ..no double pump ..plugs look good /grey..original builder said engine was built to come on at low rpm for pulling (that why high vac)..at WOT it just accelerates slowly as it breaks up..plugs gaped at 32 ..if its a weak spark where do I look this is the 3rd coil ... I had one off the old engine ..bought new one last fall thinking thats the problem....and then forgot and got another this summer lol

 

[okiemopar]

I had new points in my 383 that were shorting out to the rotor, like to have never figured it out. If your running points you might want to check it. Good Luck Ronnie

 

[pro-streeter]

Bench test the coil if you think it is ignition. Points shorting as stated, cracked cap, all connections. Is it electronic? If so check for proper ignition gapping on pick up. Also power valve should be first avaliable size under total engine vacuum. This is important as the car is loaded this adds the required fuel to over come the initial load. Just wrapiing throttle in park will not be the same effect as if the car is in motion.
Coil high side (secondary) 10,000 ohms plus or minus 2000.
Primary about 1.4 to 1.8 ohms
Just looked it up.

 

[44070dart]

its electronic..can't see it being the coil s .. 7.5 power valve ..caps fine ran it at night looking for spark jumping somewhere no dice.. thanks keep them coming

 

[70rr-brian]

Fuel filter?

 

[Mick70RR]

A friend of mine had a similar problem. Checked out the ignition first by swapping parts but it was still the same. Then I took the primary float bowl off and it was full of crap from the tank. Cleaned the carb out and fitted a good filter and it's been running fine ever since.

 

[pro-streeter]

The power valve I would recomend based on 15hg vacuum 10.5 Holley part number 125-105. I would say the power valve is not operating under the current set up.

 

[snakeoil24]

Does it stumble or does it Break UP?

A stumble is usually a Fuel Issue. A break up like quick change is more likely electrical. With the Hood open after dark spray the plug wires with a mist of water from a spray bottle and look for arching. If nothing try the cap. Still nothing spray the ground strap closest to the engine. If it stumbles shut it off instantly. Look in carb to see if accelerators are pumping fuel.

 

[44070dart]

fuel filter and tank new ..power valve not operating , hows that happen ?..I know its not ruptured (from what I've read power valve should be half of the vacuum reading ) carb pumping fuel at first crack......its definitely a break up in my mind anyway ..seems like electrical more than fuel to me ..but I'm open for suggestions ..I will try water on wires and cap tonight ..changed cap before will check again.. thanks..

 

[pro-streeter]

Two schools of thought on power valves. Holleys formula is vacuum divide by two as you stated. However the general consensus is two sizes below engine vacuum. Holleys recommendations are trying to cover a majority of applications. Mainly being stock bolt on. Anything outside of stock generally needs tailored tuning. The water trick sounds good too. Could get a light show.

 

[The Beep]

Mine did this under load. Fuel pump pushrod was worn. Not enough fuel volume or pressure under load. Changed rod and fixed. Went electric after that.

 

[44070dart]

I checked the ground wire from the engine to the firewall ...looks kind of frayed and beat up ...I don't have a large enough connector for the engine side will get one tomorrow .... ..maybe ??

 

[Archie340]

deleted

 

[pro-streeter]

Good catch. Keep us posted

 

[440ronnie67]

I guess its that time of year because mine was doing the same thing, so I upgraded to full MSD electronics, ran well but still had that spot of break up. To day I junked the edel for a preform 850 and its awesome. Between the msd and carb well worth the money even though for everything it was about $1300.