spark plug readings

Terry Stapley · #1 (**permalink**) 02-22-2005, 07:18 AM

Hi Cobra fanatics, I just replaced the spark plugs in my 418W after 3000 miles and upon looking at the plugs after removal the back two plugs on the drivers side and the back one plug on the passenger side were VERY black and damp. All other plugs were a nice chocolate brown on the porcelin and very clean looking. I am using autolite #25 plugs and wonder if I should go with a hotter plug in the 3 holes that are black or if I have another problem. Any ideas or plug suggestions would be greatly appreciated!

mark doyle · #2 (**permalink**) 03-06-2005, 04:42 PM

Are you running a vac secondaries or mech secondaries carb? Sounds like you may have a leaky needle and seat thats allowing a little drip while running. Check carb first. Then check plug gap before going hotter. If you're running an MSD box open up your gap five to ten thou over engine specs. Also fuel these days can be an issue. Try and run at least Sunoco 93 Ultra if available in your area. Good luck,
Mark

blykins · #3 (**permalink**) 03-06-2005, 07:30 PM

Are you running a Vic Jr intake?

Zoom This · #4 (**permalink**) 03-21-2005, 01:56 PM

Sniff the plug to determine if it is gas or oil. If it's oil you could have either a defective intake gasket seal, bad valve seal(s) or guides, or the rings are not sealing properly. I have a 418 stroker that had oil issues from an improperly installed intake gasket. Had to replace the gasket to reduce oil consumption. Any high oil consumption, as in 1 quart every 500 or so miles? My 418 stroker also had oil consumption problems and can be a bugger if the rings flutter at high rpm or are being pulled too deep into the cylinder bore. By the way, who built your motor?

niles · #5 (**permalink**) 03-21-2005, 04:46 PM

you must attack the symptoms logically.
first check the compression, this is why the Dr checks the BP the first thing
gn

Terry Stapley · #6 (**permalink**) 04-13-2005, 04:21 PM

Brent - I am using an Edelbrock Performer intake for hood clearance issues
Next:
The engine does not use excess oil! I did not have to add any in 2000 miles of driving!
I spoke with the Autolite rep at the NHRA races on AZ and he said the only way to read spark plugs is after a WOT pass, shut off the engine without any idle and pull the plugs. I have not done this yet. The Autolite rep recommended the same plug that I was using already!!