My spark plugs only have deposits in one spot on the insulator of the electrode. Everywhere else on the electrode is realativly clean. The deposits themselves are a textured tannish brown color and are thick enough to be scrapped off. What does this indicate about the plug and/or the engines state of tune? Im not experienced with reading plugs so forgive me for being ignorant of anything.

 

looks like trashy gas most pump gas it nasty and surely your not running anything under 93 octane are you

 

93? Heh, i run the cheapest stuff i can find since i have 8.5:1 compression but maybe now that its not getting 12mpg and 25 mpg instead i can run better gas. The lack of deposits on the rest of the plug is still puzzling. Maybe the heat range of the plug is too high? possibly timing issues?

 

I'm gonna say that maybe the build up of carbon is one spot might indicate the flame travel

Tom

 

Looks fine to me.

 

yeah....a tannish color is exactly what you want. White means lean, dark means rich.

I'd be satisfied with the color i see there.

 

Why does it only form in one patch and not over the whole insulator? The rest of it looks like new. Is it because of the direction of the flow/flame travel in the cyl? On one of them i could see the outline of the ground electrode in the patch of deposits. It appeared as a white portion in the center of the patch, as though it where shielding it.

 

I'd say its plug indexing.

When you screw the plugs into the head, the ground strap (the big hooked electrode) will face one way or the other.

The one with deposits all around it probably had the ground strap facing the rear of the combustion chamber (away from the flames) which means flame will travel all around it before it hits the ground strap.

The one with the deposits parallel to the ground strap probably had the the ground strap facing the flame. So the flame had to travel around the ground strap before it deposits on the backside there.

Plug indexing is a way to add a slight performance to the engine. Basically you mark the plug so you know which way the ground strap if facing, then you screw all the plugs in so that the ground strap is facing away from the flame.

 

dimented24x7, my take on the plugs is this: the crusted side is toward the intake valve. The 350 Goodwrench engines do not have good oil control on the valve stems. It may also be a tad on the rich side. This is what is causing the build up of deposits.

I've always found EFI engines that run stoich to have bone white spark plug electrodes. Unless other issues exist.

RBob.