burning plugs
 

I have a 440 that is burning the electrode out of the #7. #5 is showing signs of it starting to burn it has little grapes forming on the electrode and strap.
I have put a new harness in the car also new electronic dist, plugs/wirer's. It was running good at first then burned the plug? plug gap's 40. timing set @10 adv. total timing 36. After it burned the second plug it has developed a slight miss back thru the carb even with new plug. Any thoughts?

Big vacuum leak on that cylinder?

Valve or maybe gasket? No steam out the tail pipe's and the anti freeze look's clean.

I was thinking more along the lines of an intake gasket leak at the head port. Since another cylinder is starting, I'd verify that you have the proper heat range plug for you application as well. Get it figured out before you drive it much more.

How many miles on this engine?

I had a 340 do this years back and I had found that carbon on the intake valve and piston top was increasing the compression as well as causing it to run lean and burning the plug. You can pull the manifolds or run a scope down the plug hole.

Not sure on miles. It has ac 45 plugs. I tried a 46 which is one step hotter it didn't like them.So i think I'll go down one and see what happens next time.