440 cuts out at 4600 rmp help please

[Dabobo1955]

This just started a couple months ago. Stroked 440 6 pack ran great now it pulls great up to 4600 rpm. Things I did new fuel filter plugs wires cap rotor fuel pump changed msd al6 box for chrome mopar ignition system checked advance of distributor . I'm outta ideas help please

 

[PurpleBeeper]

We could use a little more information, but I will ASSUME that this engine pulled hard up to 6500rpm....and all of a sudden, out of the blue, one day it only revs up to 4600 & starts to miss....no parts or tuning change...just out of the blue.

If you start to cut out, you are running short of either fuel or air (or timing is off). My first guess would be fuel filter (but you changed that to one that you're SURE flows enough). Might be some dirt that got past the fuel filter and is now plugging up one or more of the needle & seats. Could be a fuel pump starting to go bad (what is your fuel pressure at high rpm?). It could be rust in the fuel tank that plugged up the "sock" on the end of the fuel pickup.

OK, now over to the air side of things. How clean is your air filter? Do you drive on any country roads? Are the carburetors opening up fully? If yes, how do you know? Do you possibly have an air leak in one of the secondary diaphragms or the cork seal between the vacuum diaphragm "pod" and the main body of both outboard carburetors?

Now for timing (spark & valve). Do you hear any rattle out of the valve covers? Are you running stock-type rockers or adjustable? Basically, is there any play in the valve train keeping your valves from opening fully? If you really rev the heck out of it, did you collapse a hydraulic lifter? On the spark timing, what exactly is your initial timing? Max advance? At what rpm is your max advance? What were all these numbers before you changed the distributor?

Oh yeah, one long shot is.... did you jump a tooth on your timing chain?

 

[terzmo]

few things....fuel starvation.....distributor advance......I ran a 3/8 line with my 6 pak setup...was running ok before ?? If so.....the fuel line issue is not it....I'd swap the distributor for a start

 

[67Satty]

Maybe check reluctor gap too while you are at it.

 

[cryplydog]

Valve train?

 

[lewtot184]

if by chance your are using the factory vapor separator the return line orifice is too big. this will definitely take some starch out of the top end. i've also known instances where the mufflers come apart on the inside an act as rev limiters.

 

[furryfrog]

To help diagnose if it is an ignition prob, hook a timing light up to a plug wire, strap the timing light to your hood, windsheild wipers, whatever so a passenger can see the timing light flash when your driving.

 

[Dennis H]

Elaborate. Completely, stumble? Is there a rev limiter in the car.

 

[bigmanjbmopar]

Burnt plug wire

 

[kiwigtx]

In the days of points in my '70 Roadrunner with a 440, the condenser just burnt out after a 2-mile run at around 150mph. Ignition just died....coasted about another 2 miles though. :yes: (In the days before fancy cop radar and spotter planes out on the Desert Rd).
Got transported to the local garage for an easy fix - I always carried a spare after that.

 

[383man]

if by chance your are using the factory vapor separator the return line orifice is too big. this will definitely take some starch out of the top end. i've also known instances where the mufflers come apart on the inside an act as rev limiters.

If you do have that setup with the vapor separator you could try clamping off the return line and driving it to see if it runs better so it wont let fuel pressure drop if that is the problem.
But I do agree more info would help alot. Does it start missing when it happens or does it just lay down without missing ? Just a better description may give us a better idea what we think it is. Ron

 

[AR67GTX]

Not clear which distributor you are running but the symptoms I always experienced with worn distributor bushings in a Mopar distributor was a break up of ignition and missing at over 4000 rpm - and with points you can see the dwell jumping around as the motor is reved up. And worn distributor bushings was inevitable on a stock Mopar distributor after several tens of thousands of miles. I think some electronic ignitions you can still pick up a dwell reading on a meter - but not sure on that.

 

[moper]

Why was the MSD removed? When in relation to that did the problem start?

 

[Dabobo1955]

Ok the engine has 2 inch Doug headders open no fuel pressure gauge a 440 source distributor oh new blaster coil . I took the msd box out after the problem started trying to eliminate possibilities.
I appreciate all the timely responses thanks

 

[Shorthorse]

Lots of good questions being asked by other posters. A little more information please. What exactly does it do at 4600 RPM's?
Does it just stop pulling but the engine appears to be firing on all cylinders?
Does it break up or backfire?
Does it do this only under a load but seems to free rev OK?

 

[Dabobo1955]

Lots of good questions being asked by other posters. A little more information please. What exactly does it do at 4600 RPM's?
Does it just stop pulling but the engine appears to be firing on all cylinders?
Does it break up or backfire?
Does it do this only under a load but seems to free rev OK?

Just breaks up and stays at aro5that rpm like it hit the Rev limiter

 

[coz]

Valve train?

valve springs???

 

[Kern Dog]

Maybe check reluctor gap too while you are at it.

YES

I had mine slip from .008 to .020 more than once. The car would idle fine, cruise fine but stumble and cut out at WOT.

 

[Garys1969RR]

First determine if its an electrical or fuel prob. Sounds like an ignition prob, since it starts missing at exactly the same RPM each time.Try the timing light tied to the hood test , as described earlier by furryfrog. Then if it begins to flash erratically when the engine starts to miss, then you have narrowed it down to an ignition prob.

 

[plymouth67]

I was thinking valve springs also...