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Re: plug fouling (again), what to do? (archive)

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Posted by sean on September 10, 1999 at 17:13:05:

In Reply to: plug fouling (again), what to do? posted by Corey Turner on September 09, 1999 at 12:35:56:

: I've just fouled 2 out of 4 plugs for the third time in about 3 weeks. This only 10 days after I got the car back from the mechanic.

: Disclaimers applying being that the engine is very shortly going to be swapped for a new one, for reasons of needing a valve job, burning tons of oil, and lots of blowby.

: I'm running dual 40 DCOES, just professionally synched and adjusted. Also a MDS 6a triggered by a stock distrib running to a bosch red coil.

: The car idles now smoothly at 1.3k, it doesn't idle smoothly at all under 1k. Er, it does when it has clean plugs anyhow.

: I am in Charleston, which is extremely hot and humid this time of year. I also park dowtown in a parking garage only 1.5 miles from my house, so my commutes are too short to even get the car completely warm, usually. On the days when I have to run all the way up to the top 8th floor of the deck, I find myself apologizing profusely to the car, as I cant help but feel badly about using those 4 synchronized barrels to inch up through the traffic of the garage.

: Im concerned about running too lean if i start playing with the idle screws. I understand fouling is caused by too rich, but how do you tell if you are going too lean?

: Any help appreciated.

: Corey


First, walk to work.

It's tough to set up the carbs on a clapped out motor with bad compression because not only is vaccum low, it can be incosistent.

If you lean out the mixture screw you won't damage the engine because you're on much larger circuits when you put your foot in it. A good rule to follow is "best lean idle". Let the car warm up and with the idle around 1000 rpm, adjust the mixture screws in till the car starts to stumble then back them out till the idle is smooth. Next, turn the idle stops down to where you want your idle rpms.

Champion used to supply a spark plug reading chart for drag racers - I don't think its available any longer, but they are helpful. Gas has so much weird stuff in it now, though(in USA), that color readings aren't as easy to go by as they once were. Generally, you're looking for a light brown or rusty residue in a motor with good compression and properly set timing. Good race gas will be tan to greyish white.

The thing to do with your new motor is to rent some dyno time and jet there, altough backyard tinkering usually gets ya close enough!

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