Spark Plug Help!!!!!

l8rbra · Jan 26, 2007

Hi all. Recently got a 98 Cobra with a Novi 2000 w/ aftercooler and a ton of extras (still figuring out some as I got it from a dealer). So I changed the spark plugs which I have done a dozen times in previous stangs but when I started back up it runs like **** with white smoke pouring out the back. Smells very much like fuel. Well...idiot me unplugged on of the injectors to get the part # (again...still figuring out whats on the car) and didn't plug it back in. I plugged it back in but still have the same result. I removed a couple of the plugs just to make sure they were seated right and they are all black. Looks like instant carbon buildup or something.

BTW...the two plugs closest to the firewall (one on pass and one on driver) were oily when I picked them out originally.

The car ran OK before this "maintenance" so I am wondering what I couldve jacked up in changing the dumb plugs. I gapped them at .033

Thanks for your help all!

Uncle Meat · Jan 27, 2007

What brand and heat range plugs? May be too cold or improperly gaped.

U.M.

l8rbra · Jan 27, 2007

Autolite 764s gapped at .033

TheCrazy1 · Jan 27, 2007

Hey! Congrats on your new ride... I have a 98 Cobra as well. The Autolite 764's are the right ones for it, but the gap that's usually called for is .052, that is unless the modifications require anything different. Try resetting the gap and see how it runs, making sure no plug wires or injector wires accidentally got crossed. The oil you saw could be caused by the valve cover gasket leaking around the spark plug holes. Mine has one or two that leak a little bit and I've heard this is a common problem, but changing those gaskets is a time consuming job!

l8rbra · Jan 27, 2007

Hey guys...thanks a ton and I'm on my way out to regap. Appreciate the help and hopefully I'll be back up and running soon!

blackfang · Jan 27, 2007

That is your problem right there. You are not using the right plug. 764's arent to be used with a forced induction engine.

TheCrazy1 said:
Hey! Congrats on your new ride... I have a 98 Cobra as well. The Autolite 764's are the right ones for it, but the gap that's usually called for is .052, that is unless the modifications require anything different. Try resetting the gap and see how it runs, making sure no plug wires or injector wires accidentally got crossed. The oil you saw could be caused by the valve cover gasket leaking around the spark plug holes. Mine has one or two that leak a little bit and I've heard this is a common problem, but changing those gaskets is a time consuming job!

Bad advice! You can not have that plugged gapped for a NA motor when its supercharged.

l8rbra · Jan 27, 2007

The plugs I pulled were 764s and I have seen others on the board use them with no problems. Any reason why 764s are no good?

Everything I read was in the .030 - .035 range. The ones I pulled out were at .050. I put them back in at .040 and she is running like a champ. I guess there is a chance I didn't set one right the first time (freaking things are in that hole so deep) but I will say I am confused. For sure don't want to do any more damage than the last owner. The aftercooler (water cooled) had a busted hose, the intake was full of mud mounted in the fender with no protection from the tire, no turn signals, and the list keeps going. Was a sucker to buy it from the dealer but it was paying blue book for the Cobra and getting all the extras for free.

Got some work to do to get her back in shape : )

Thanks again to the board for helping out.

blackfang · Jan 27, 2007

l8rbra said:
The plugs I pulled were 764s and I have seen others on the board use them with no problems. Any reason why 764s are no good?

They are for a stock replacement, not for a Forced Induction setup like yours. I would use Autolite 103's or AR 94 to be safe which are 1, and 2 heat ranges colder.

Everything I read was in the .030 - .035 range. The ones I pulled out were at .050. I put them back in at .040 and she is running like a champ.

I was commenting on the poster above telling you to gap the sparkplug at .054. He apparently didnt read you were using a blower. That is incorrect and could lead to spark blowout.

Kilgore Trout · Jan 27, 2007

Motorcraft AGSF-12FM1 @ .044 is correct

You could take the gap down as low as .035 if you think you are getting blowout.

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