i have a 350 that has 20 k on it and everytime i change my plugs they are black with alot of carbon on them.i used to have a realy lean jetted carb so i dont understand why they still had carbon on them. i currently have a 750 edel wich is what is recomended for my combo by edelbrock.still the same plug condition. i was wondering if maybee my plugs are too cold.i have been running bosch platinum single tips. i estimate my compression is around 10.5. what would be the best plug for me to run?

 

If your cam is Edelbrock part # EDL-5002,
then that's why your plugs are doing that.

 

yup. thats the part number. what causes them to do that? how can i fix it?

thanks
jeff

 

Too much duration & overlap for the RPM range you're running in. That cam is not its best at idle and cruise RPMs.
When the intake and exhaust valves are both open at the same time (overlap) you get reversion. Exhaust gas will get pulled back into the chambers during the intake stroke. This both cools the combustion by diluting the charge (like EGR) but introduces a lot of combustion byproducts (soot). That cam is designed to operate at higher RPMs where there is no time for reversion.

The best you could do without replacing the cam is to advance it (the cam) a few degrees so the exhaust closes a little sooner relative to the intake stroke. Advancing the cam normally picks up the bottom end power a bit, though the best solution is to use a different cam more suited to daily use.

 

ok i get it. my cam already was advanced 4 since i put it in. but i was wondering if all larger cams will do this to plugs. i have a few friends that run a pretty good sized cam and ive never realy heard of them having a problim with plugs. thanks again.