440 Slight popping/hesitation/cutout under acceleration...

[The Dartman]

For those of you that visited my “Bench Race my combo!” thread, this is going to sound familiar, but here goes:

This is a brand new rebuilt 440, that was built as follows: 1978 440, 30 over, cast crank, 10.22:1 CR, 516 heads, fully ported and polished, 2.14/1.81 valves, Mopar Hydraulic .509 Camshaft, non adjustable valve gear, Mopar M1, 1 Inch 4 hole spacer, Holley 750 double pumper.

My car went to the race track two weeks ago, but I was unable to race. The car would pop and backfire out of the passenger's side, getting worse as the car revved up. At idle it was barely noticeable. I changed plugs, timing, adjusted my carb, and tested the plug wires all without finding the culprit. I also checked for a flat cam as well. After chalking up the day as a loss, I put it back together to put it on the trailer, and a funny thing happened... It ran better! I noticed some slight pops when I punched it hard, but I was able to get on it a little on pit road to see how it ran. It revved so fast I hit 6 grand in low in the pits! I immediately ran right up to get the car in staging lanes, and it started drizzling and later the skies REALLY opened up and dumped some serious rain down.

I went to the track the next week, and almost got rained out again but I did manage to make two passes. The car still had some issues, and the pops, cutouts, hesitations continue but at a fraction of the week before. I wanted to rule out carberation, so I borrowed an 800 CFM Holley carb off my friend's 11.40 Duster. I thought everything might be okay, but it wasn't...

The car a best of 12.07@110, with a 1.73 60 foot time.

Not too bad when you consider how bad it was popping and cutting out throughout the RPM range, but there’s another 3-4 tenths on the table to be had once this problem has been addressed. My Dad described the problem as “floating” or “fluctuating”. I don’t know if I would describe this as cutting out, hesitation, or popping, but it happens sporadically all throughout the RPM range and will not do it unless the car is in gear and under a load (light to heavy acceleration).

I am planning on replacing the plugs, wires, cap, rotor, and distributor for next year and see what I come up with. The funny thing to me is that is idles and revs up fine in nuetral, but once in gear and under a load, the problem starts. This MSD 6AL was tested late last year, so I do not expect that it is the problem. I also don't believe that the problem lies in the valvetrain either, with either with a bad spring and a flat cam (which I already casually checked for). The plugs are gapped to .040, so they should okay as well.

Any thoughts?

[WayneT]

Have you checked the timing with a light? From what I remember setting the timing on my 440, I had too much initial (I think) and the engine would hesitate and surge off idle. In park the engine revved real nice. Also check the advance springs in the distributor to see if one is broken or not attached.

[REDNECKMOBILE]

Get your multimeter out and test for voltage and resistance but first clean all connections and look for a possible burned or stressed wire. It's easiest if you got a friend with the same setup then switch parts until you find the problem otherwise have fun metering.

[Crank]

do a compresion test if you think its internal, but it sounds like a fuel presure problem what size fuel line are you using?

[The Dartman]

The fuel lines are 8 AN to the regulator, 6 AN to the carb. Aeroquip and other vendors state that 6 AN can support the fuel requirements of a motor that makes 1000 HP. That's good enough for me. While troubleshooting the problem, I did crank up the pressure from 6 to 7.5 PSI as well.

Thanks for the replies...
Dartman

PS - Looks like one of my other posts is also missing. The distributor is slated for replacement as well. It has recurve springs, and it set to come all in by 1800-2000. It has no vacuum advance, and the plates have been JB welded to hold it in place.

[waynebo]

Sounds like your getting small trash in your carb,it clogs a jet or to partialy and then sucks it through,check your filter and clean your carb,wayne

[The Dartman]

The problem was there with my 750 as well as the 800 I borrowed off of a 11.40 Duster that was running fine, so that pretty much rules out carburation in my book.

Thanks! Dartman

[rumblefish360]

Sounds like lean and/or to much advance. Being new to a big block myself, I found the distributor a bit touchy.

[REDNECKMOBILE]

Have you checked the distributor to see if the pointer is in correct relation to the cap, sometimes the junk sold today will be off index and you're getting a crossfire between tow posts. Try to find a a store that sells Standard products and buy a new pointer and cap if you find the distributor firing out of index.

[The Dartman]

I am thinking an out of phase condition might exist. I have bought the same type of distributor before for my SB, and found that the wires were reversed. It took me about three weeks to even try to reverse the wires, and it fired right up.

Not to mention that I pulled the reluctor myself to replace the springs. Although I made absolutely certain that it was installed correctly, I could have feasibly installed it backwards.

The other thing that I am also suspecting is that when I removed the vacuum advance and JB welded the plates, that the vibration COULD have broken the JB weld and the plate is floating around loose in the distributor. I have doen some checking for this already, but it is also a possibility.

Dartman

[party340]

Are you running a vaccume advance? I'd bet a 100 dollars if you are thats your problem. Disconect the thing and try it. The same thing happend to me when I welded the slots in my dist. The vaccume advance worked like crap after that. (poped and drove like shit) I had to end up putting a advance from a points dist. to make it run right. Also check the gap between the pickup and the other thingie? Its suppost to be .008.

[The Dartman]

The entire vacuum advance assembly has already been removed. I like your conviction though!

Dartman

[Crank]

party 340 i had checked the .008 on one of my car's and it was all over the place it drove me nuts for weeks .one spot i checked was .008 or 7 i don't remember but all the other's were from 5-17 i replaced the rotor or cam???what do you call that thing.by the way the distributor was brand new mopar performance replacement and ran great for over a year before the problem.i still to this day can't figure out what happened to cause this or if it was that way or wore out some how?

[mr.b]

i agree with redneck, you may have an electrical breakdown esp under load. i noticed you changed several items but not your plug wires. even after inspecting them they may still be bad. fairly cheap to do. or an electronic module may be intermitent.