Hello all,

I'm trying to figure out whats going on with this plug. This is #8 cylinder. I recently installed a new crate engine in my suburban which has the edelbrock 3502 MPFI conversion. New GM crate engine has about 4500 miles on it. The image below is a new plug with about 2 hours of run time on it. The last new plug removed looked exactly the same. The burnt spot on the insulator is only on one side of the plug, the rest of the plug looks clean. Spark plug gap is to spec.

https://s18.postimg.org/91xeyhr9l/Splug.jpg

Splug.jpg

Any thoughts on what is causing this? My mileage on the truck is down a few MPG and I'm sure this cylinder is the cause. I'm not sure if that burnt spot is facing a valve or something else. I did a quick look with a borescope in the cylinder and didn't see anything horrifying but there was some carbon on the piston face which seemed strange for an engine with low mileage.

Any thoughts would be appreciated.

Thanks
Eric