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Discussion Starter · #1 ·
I have a mild build 350 in my 54 pickup that started missing under load yesterday after coughing back through the carb.

The motor is dished piston, 30 over 350, rebuilt 487 heads, Edelbrock 2101 cam kit, 1406 carb, performer manifold and a brand new Mallory series 85 HEI distributor. Timing is set at standard specs with the vacumm advance connected to manifold vacumm.

The carb choked up while crusing at about 45 mph and after that it began running very rough. At idle it seems fine and under acceleration it smooths out but at a constant cruising speed it feels like it dropped a cylinder.

I have pulled the plugs and all have a light brown tone to them. Vacumm lines appear fine but when I pull the line off the distributor it does not seem to have much if any effect.

Everything was fine until this cough back. Any suggestions on how I can track this problem down?
 

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No PV on an Edelbrock Performer 1406 carb, guys.

It may have jumped timing, it may have a broken valve spring, it may be a lot of things.

I would start by checking where rotor is, with the timing tab and balancer mark at TDC.

If that's OK, check the vacuum and see what that tells you, if anything.
 

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Discussion Starter · #6 ·
Thanks for the hints.

I checked all the vacumm lines and found one T fitting that cracked but I also found the boot on the #5 cylinder was crumbling from heat. This is with heat socks on too! Now I know the difference between the cheap wire sets and the expensive ones. Glad I had saved a few of the wires from the previous set to tide me over until I get the new ones on order.

Does anyone have a recommendation on an HEI wire set that has 90 degree plug boots?
 

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I'd say it's the plug wires. It will cause miss under heavy load. The wires could be jumping to another wire if touching each other. I'v seen that happen so many times when customer called me wanted me come to their garage to slove their problem.
 
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