1996 90 crossflow failure question

[bills2004svt]

Hi my 1996 90 crossflow looks like it may have dropped a cylinder the lower starboard one. First question is what would have caused 1 to do this. The spark plug had little spatter pieces of aluminum and the compression dropped like 20 psi. I pulled the carbs and the bowls were clean jets looked good. other three cylinders look good. Second I have decarbed the motor twice htis year the pistons looked clean. Any other suggestions?

 

[freetime99]

Re: 1996 90 crossflow failure question

Do you have access to a small scope ? I'd look inside that cyl. from the spark plug opening and see if the piston has a hole. Otherwise, I'd suspect that a piston ring has broken, Also, make sure the threads for the plug aren't stripped. That metal you're seeing is coming from somewhere. Next step would be to remove the cylinder head and inspect.

 

[bills2004svt]

Re: 1996 90 crossflow failure question

Im going to pull the head. it actually runs pretty good just a faint knock it seems. Is that particular cylinder prone to failure?