Beating my head against the wall. Sbc random missfire

[Stealth]

#2 cylinder fires great when the motor is cool, as soon as it hits 150 degrees it randomly fires. What I have done: leak down, swapped msd boxes, swapped wires, checked and rechecked valve adjustment, intake gaskets, new distributor cap and rotor.... I am running out of ideas and all of these things checked out.

A little bit about the motor: .60 over block. 13ish-1 comp, dart aluminum heads, edelbrock Vic jr intake, running e85

 

[Stealth]

Whole upper end has probably 60 miles on it... Everything is in spec for those parts

 

[CWPottenger]

You didn't mention changing plugs?

 

[81msw79]

also pull the distributor and check the condition of the gear. I had the same problem on my blazer. it ended up being a heavily worn distributor gear.

 

[chevy2480]

You didn't mention changing plugs?

+2. Could be a bad plug. I had a autolite plug does this to me. Once screwed into head it would ground itself out. Brand new out of the box.

 

[hurst1979olds]

How do you know its #2 cylinder?

 

[MD13ailey]

try the coil. They can work wheb cold and stop working when hot. Since you are running higher compressio. It might be just starting to fail and undervolting.

Only.other thing I could guess is to close your plug gap to .030" or .025" the higher compression could be "blowing it out" and obviously cylinder pressures rise when the engine is warmer

 

[GhettoRacingKid]

try the coil. They can work wheb cold and stop working when hot. Since you are running higher compressio. It might be just starting to fail and undervolting.

Only.other thing I could guess is to close your plug gap to .030" or .025" the higher compression could be "blowing it out" and obviously cylinder pressures rise when the engine is warmer

^^^^
This....

Whats your gap at? what MSD are you running, what type of pick up? change the plugs, You sure its just one cylinder? or it is a few of them? whats your voltage and Amperage?

 

[Stealth]

Plugs have been changed, distributor gear is fine... I know it's #2 because that primary tube is considerably cooler than the others

I am running a msd 6al with a pro billet dist and a blaster coil

I close the gap on the plugs

Running 13.5 to 14 volts

 

[CWPottenger]

Plugs have been changed, distributor gear is fine... I know it's #2 because that primary tube is considerably cooler than the others

I am running a msd 6al with a pro billet dist and a blaster coil

I close the gap on the plugs

Running 13.5 to 14 volts

Closing the gap will actually have the opposite effect you want unless they were already too large a gap. You are running E85 so you need more "heat" in the cylinders. I'm not familiar with the Victor jr intake, but you may have some issue with fuel delivery to the cylinder from a burr or other small imperfection in the runners. You may need to install the next heat range up plug to properly ignite the mixture.