I recently put a rebuilt 351w in my 66 mustang. The heads were also redone. From the very beginning the #4 cylinder was tapping and only gets worse as the car warms up. I took the plugs out and the first three are nice and clean but #4 is black with carbon. I took the head off and the stem of the #4 valve is also blackened up. I've been told it could be the valve is bad or the timing is off and a host of other things. Any information would be greatly appreciated. Thanks. Tom.

 

is the piston top black?

did the car smoke? if so, what color smoke (blueish, white, black)?

are both valve stems black or just one? if one, which one?

any scoring on the cylinder wall?

what kind of tapping? metallic hammer or more of a slapping sound? does it sound like it's tapping at full or 1/2 engine speed?

assuming it's a solid lifter engine, did you break in the cam correctly?

any metal flakes in the oil? split the filter and look in there too.

 

Thanks for your advice. I pulled the lifters out today and there was no scoring on them but a few of them had some small chips around the edges. Not sure what happened there, but I'm sure it isn't good. Cylinder walls and everything else looks fine. I took the engine out this afternoon. I'm gonna go over it again and put a new cam in it. Thanks for your help.

 

sounds like you didn't break in the cam correctly. here's a random article i found that explains the procedure fairly well:

http://www.carcraft.com/howto/ccrp_0...cam/index.html