Advice? 3 Cylinders

[splitworld]

So I had my type 3 running great after i got her tuned up but it started running shitty again yesterday.  I checked it out and #3 cylinder was not firing anymore,  I switched the plugs with another cylinder and suddenly I was back in business.  But not for long.  I am back running on 3 cylinders again.  I cant figure out why the #3 cylinder keeps burning out.  Timing is good, wires are new, plugs are new, carbs are new, heads are new. WTF Is it burning to hot? should I put a higher temp plug in?  Any help would be greatly appreciated.

[Cameron]

I cant figure out why the #3 cylinder keeps burning out. 

Define "burning out".

Checked valve lash lately?

What kind of carbs? I'm thinking there may be a clogged idle circuit.

[splitworld]

Valves are adjusted.  I changed the plug again today to a cooler burning plug, runs even worse.  I've got duel 34 empi.  Cant say for sure the plug is burning out but when I pull the wire off to that cylinder there is no change in the engine performance.  I had 2 different carbs on the car, still the same problem.  with the new carburetors it makes it very hard to do a compression test.  Im really flat for Idea's the car has a mind of its own.  The thing that bothers me is that it ran perfect for like 3 days. 3 cylinders is cursed.

[egspot]

I am no expert but, check your cables from dist to plug and your rotor, dist cap etc.

[splitworld]

yeah checked the wires, and cap, and changed them both.  Im thinking now that a valve might have gotten stuck in, when I got the heads rebuilt maybe they didn't seat the heat properly, but ive got to pull the motor again.....no fun for summer