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440 six pack issues

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Bee Bob

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I need some help with my six pack set up. The engine spits and sputters at 3500 rpm and will not come out of it. Timing is 17 base and 36 all in. Carbs are new, Carter street pump, I am pulling 14 inches of vacuum with a Comp magnum cam. I installed Promax plates for interchangeable jetting. Any help would be appreciated.
 
The fist thing that jumps to my mind (& I'm not sure I'm right) is "possibly" the air bleeds in the Promax outer carb plates. I'm running Promax in my outer carbs & they come with MUCH larger air bleeds than the stock six pack carb plates did. They're not listed on Promax's website, but if you call them you can get replacement air bleeds for about $5/set (need two sets).

You can unscrew the air bleeds with a tiny allen wrench. One of my four air bleeds I had to take a propane torch to so I could get it out.

493Mike has a good idea. At 3500 rpm you should be opening the outer carburetors. Maybe you don't have enough fuel for all three carbs? Maybe the needle/seats are stuck on the outer carbs?
 
Last edited:
I ran a fuel pressure check today. 5.5 @ idle and up to 7 psi at higher rpm. What jets should I be running in my outboards? I changed the metering plates due to the engine cutting out at 3500 rpm but so far has not fixed the problem. The carbs are new and the floats are set correctly and needle and seats are good. Help me !!
 
Bee Bob,
I'll check tomorrow in my notes to see where I am/was.
Mike
 
Bee Bob,
My combo: 493, RPM heads (cleaned up pockets, back-cut intake valves), Hughes flat tappet cam and kit (HTL6064BS), 10.5:1 CR, Doug's 2" headers with 3" X-pipe system, Flowmaster Delta 44s, Dynamic converter, and 4:30 gears.
Intake is factory aluminum and carbs are set up per Chrysler's recommendations: Engine Manual specs for Super Stock.
I wound up with .136" holes in center throttle plates and .086" in both secondary throttle plates, Secondary idle screws at 1 1/4 turns out and went from #80 mains in outboard carbs to #90s to achieve a 30 HP gain at rear tires at Steve Morris's chassis dyno. 35 degrees total advance.
Oddly enough another 20 HP appeared when I opened my exhaust cutouts. I guess those Delta 44s are rather restrictive!
Before the dyno tune the best test & tune time was 11.64 @ 114 through the mufflers and air cleaner. Hope this helps you out! Mike
 
PurpleBeeper said:
The fist thing that jumps to my mind (& I'm not sure I'm right) is "possibly" the air bleeds in the Promax outer carb plates. I'm running Promax in my outer carbs & they come with MUCH larger air bleeds than the stock six pack carb plates did. They're not listed on Promax's website, but if you call them you can get replacement air bleeds for about $5/set (need two sets).

You can unscrew the air bleeds with a tiny allen wrench. One of my four air bleeds I had to take a propane torch to so I could get it out.

493Mike has a good idea. At 3500 rpm you should be opening the outer carburetors. Maybe you don't have enough fuel for all three carbs? Maybe the needle/seats are stuck on the outer carbs?
Click to expand...
shouldn't be any air bleeds in the metering plates. your probably looking at the idle feed restrictions.
 
Bee Bob said:
I ran a fuel pressure check today. 5.5 @ idle and up to 7 psi at higher rpm. What jets should I be running in my outboards? I changed the metering plates due to the engine cutting out at 3500 rpm but so far has not fixed the problem. The carbs are new and the floats are set correctly and needle and seats are good. Help me !!
Click to expand...
maybe it's not a carb problem?
 
Sounds like an ignition problem maybe
 
This has me stumped. I also thought it may be an ignition problem but I have had two distributors in it, changed the ECU and ballast and had the timing all over the place. The odd thing is the engine will red line when in park. This only happens under load while driving but it happens every time. I did tie the outboards closed and rpms will climb to the max. It is doggy but it will do it just on the center carb. Any ideas ?
 
Bee Bob said:
This has me stumped. I also thought it may be an ignition problem but I have had two distributors in it, changed the ECU and ballast and had the timing all over the place. The odd thing is the engine will red line when in park. This only happens under load while driving but it happens every time. I did tie the outboards closed and rpms will climb to the max. It is doggy but it will do it just on the center carb. Any ideas ?
Click to expand...
it's possible to have a fuel pump that will produce pressure without pushing any fuel. do a fuel pump volume test. look for any possible air leaks on the suction side of the pump.
 
I also wonder if the promax plates are not letting the floats drop in the end carbs and basically starving them for fuel. this has been a problem with those add on plates. put the stock metering plates back in the end carbs and retest. I'm very cautious about re-engineering these carbs.
 
lewtot184 said:
shouldn't be any air bleeds in the metering plates. your probably looking at the idle feed restrictions.
Click to expand...

Yep, Lewtot is right on this...my mistake. And when I think about it, the idle feed restrictions would primarily affect idle, not high rpm.

What do you mean "spits & sputters at 3500rpm and WON'T COME OUT OF IT?" I'm confused what you mean exactly.

Also, "rpms will climb to the max. It is doggy but it will do it just on the center carb."...this isn't clear to me what you mean either.

Lewtot's other ideas on stuck floats and/or pinhole fuel line leaks are reasonable too. My Promax floats didn't stick (checked VERY carefully), but I've heard of that happening.
 
Check voltage at coil.

I had low voltage at coil, engine would idle and rev ok until I put a load on the engine, then it would fall on it face, backfire until I got out of throttle. Low voltage due to corrosion on electrical contacts, I did not need ballast resister so I ran relay from batt to coil.
 
That's exactly what mine is Doing! Voltage at positive side with key on is 5.8 . What should it Be? The car has a new dash and engine harness.
 
Thanks Carcinogen ! What I thought was a carb issue turned out to be an ignition issue. I unplugged the tach wire in the dash and the problem went away ! If it's weird it will happen to me ! Thanks everyone. Bee Bob
 
i've had those tach wires short out. usually it just kills the engine.
 
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