Help!!

[AKBullDog]

I have a 1965 Plymouth Belveder. It has the original 383 block, but that is about it. Recently, it has started to sputter, cutout, of miss fire when I am at high RPMs. It runs very well off the line, but when the motor hits higher RPMs it just starts to sputter. The motor has about 1500 miles on it. Lunati cam, stealth heads, Keith Black pistons, etc. I am afraid that it is a flat lobe on the cam. Any ideas?? HELP!!!!!!!!!!!!!

 

[67 coronet]

first thing to check is if you are running it out of fuel.what is your fuel delivery system and carb setup?

 

[krowbar]

first thing to check is if you are running it out of fuel.what is your fuel delivery system and carb setup?

x2

 

[AKBullDog]

I have an electric fuel pump run through a regulator with about 5 1/2 PSI. The carb is a holley 770 street avenger. This set up has run well, until recently. I first thought it might be the electric fuel pump, because I did not have a return line set up to the gas tank. Figured that the pump was overheating and not able to keep up with the demand. So, I returned to the mechanical carter pump and the same thing. I did install new fuel line from the electric pump, installed at the rear of the car, and reused this when converting back to the manual. This is a nice thick fuel line, so I would not think that the line would be collapsing under heavy load, but not sure.

 

[krowbar]

Collapsed lifter is like a worn lobe too. Check your rockers and springs. timing weights might be sticking in dist.

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What rpm's are you having trouble through?

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Bad coil?

 

[Pops1967GTX]

first thing to check is if you are running it out of fuel.what is your fuel delivery system and carb setup?

X3 .....A plugged fuel filter, crushed fuel line or clogged pickup screen inside the fuel tank can all starve your engine for fuel. If not fuel,I would bet your problem is electrical/ignition.

 

[krowbar]

Vacuum or mechanical secondaries?

 

[AKBullDog]

Collapsed lifter is like a worn lobe too. Check your rockers and springs. timing weights might be sticking in dist.

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What rpm's are you having trouble through? I believe right around 5k or a little higher.

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Bad coil?

I was hoping such an easy fix. I am getting ready to dig in, so that will definitely be one of my first looks.

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Mechanical

Vacuum or mechanical secondaries?

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I am running 2 filters. One prior to pump and then one out of the regulator. The gas tank is original, so I am not sure what kind of internal filter/screen is in place. I will look into it. Thanks!

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Collapsed lifter is like a worn lobe too. Check your rockers and springs. timing weights might be sticking in dist.

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What rpm's are you having trouble through?

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Bad coil?

Just thinking about it. When this stated happening, My ignition switch went bad and I had to replace it. The car would start, but as soon as you let the key go back to the run, it would die. If you held the key, just short of the run position, it would run. I just replaced that last night, but found that the high RPM problem still there. Could these be related?

 

[krowbar]

I was hoping such an easy fix. I am getting ready to dig in, so that will definitely be one of my first looks.

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Mechanical



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I am running 2 filters. One prior to pump and then one out of the regulator. The gas tank is original, so I am not sure what kind of internal filter/screen is in place. I will look into it. Thanks!

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Just thinking about it. When this stated happening, My ignition switch went bad and I had to replace it. The car would start, but as soon as you let the key go back to the run, it would die. If you held the key, just short of the run position, it would run. I just replaced that last night, but found that the high RPM problem still there. Could these be related?

If it's dies when it switches back to run then your ballast is probably bad, if you still have one hooked up. If that's the case then the way you're doing the half key thing is probably sending battery voltage to the coil while running and maybe overloading the spark at high revs.

 

[AKBullDog]

If it's dies when it switches back to . then then your ballast is probably bad, if you still have one hooked up. If that's the case then the way you're doing the half key thing is probably sending battery voltage to the coil while running and maybe overloading the spark at high revs.

I replaced the ignition switch and it solved the half key thing . It starts with the key normally now. Start and let the key go and it stays running.

 

[67 coronet]

still sounds like fuel.check the pre pump filter and blow through it or check for debris,depending on design.stumble could be an ignition break down,but that is hard to find when limmited to upper rpm stutter.you end up just changing parts and guessing.when you were 1/2 turn keying it,you were sending full 12 volts to the coil and could have damaged it if you drove like that for a good amount of time.hard to say with out an eng scanner or old occiliscope.

 

[hashmaker]

1500 miles is about how long the cam would go if it started to fail from the begining. Did you break it in right, use the zinc based additive before and after that first oil change? Valve springs too stiff for proper break in? If all the above fails I would look at the rocker arms and make sure they all move as they should.

 

[furyus]

If a cam lobe was going flat, It would miss at all rpm. Same with a collapsed lifter. Are you still running a ballast resister? What ignition system?

 

[AKBullDog]

If a cam lobe was going flat, It would miss at all rpm. Same with a collapsed lifter. Are you still running a ballast resister? What ignition system?

Yes, I am and yes it was. The ballast fixed all!!!!!!!!!!!!

 

[Bolt-Action]

Depending on how long your ballast has been bad, keep a close eye on your coil, its the ballasts job to reduce the voltage to your coil, if it went bad, it's been cooking your coil and it could potentially fail on you, throw a spare coil in your trunk, just in case.

 

[AKBullDog]

Thanks man!

Depending on how long your ballast has been bad, keep a close eye on your coil, its the ballasts job to reduce the voltage to your coil, if it went bad, it's been cooking your coil and it could potentially fail on you, throw a spare coil in your trunk, just in case.