Spark Plugs 351C 2V

Got the mustang out and started to do some tuning. I plug the plugs out (351C 2V) and notice that they were a little rich. At the beginning of last year I had champions in there and they were grayish in color and looked good. No that I switched to Motorcraft there looking a little too rich. So is it the plug or carb? What is the recommended plug I should use Champion or Motorcraft?

Someone recommended NGK UR4GP so that's what I've got.

Doc

I run stock motorcraft.

Got the mustang out and started to do some tuning. I plug the plugs out (351C 2V) and notice that they were a little rich. At the beginning of last year I had champions in there and they were grayish in color and looked good. No that I switched to Motorcraft there looking a little too rich. So is it the plug or carb? What is the recommended plug I should use Champion or Motorcraft?

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How many plugs are rich?

If not all, which cylinders?

How many miles on the plugs?

What kind of ignition? Stock points, aftermarket(what kind), other.

Leaving all your plugs in the car, connect a good used or new spark plug to an ignition wire, ground the threads of the plug to the car, start up the car, and see what kind of spark you get.

How many plugs: 8 are rich looking and consistant

All cylinders are the same after pulling the heads off and taking a look.

500 Miles on the plugs. Very new Motorcraft plugs. They are the plugs spec to the engine

Ingition: Petronix I, standard coil and spark plug wires, distributor and rotor

It could be both the carb and/or the plugs. The carb may need to be re-jetted to provide a better fuel mixture. The plugs may be too cold if you have made modifications to the engine. On your new plugs look for the area where the ground electrode heat transition stops. What I mean is you should see a transition area where the electrode changes color (slight bluing). This transition should be between the base of the electrode and the first thread on the plug body. After that re-jet the carb if the engine is not burning clean. I ended up a heat range hotter in my Cleveland. BTW I use Motorcraft plugs exclusively in Fords.

In a stock engine, If all 8 are fat (rich) I would suspect the carb/choke/timing. What changes were made, if any, between the time you used Champion and the Motorcraft plugs? Chuck

No changes were made to the carb or any other ignition part other than going from champion to Motorcraft stock plugs.

The entire base and tip of the plug is black. The timing was set to 8 degrees and started well at this point. Not sure if I should go up to 10 degrees. Also the Carb is not stock its a Holley 4160 (4V) on an Elderbrock manifold. The gas I use is octane level 93.

With the engine at operating temperature, I'd start by setting the timing with a vacuum gage, at least go to 10 degrees. Second reduce the jet size 2 numbers at a time until the plugs start to get clean. Check the choke to make sure it is completely off at operating temperature.

Make sure the plugs are the recommended heat range.

Champion 3025 with good results.

mike

All cylinders are the same after pulling the heads off and taking a look.

Ingition: Petronix I, standard coil and spark plug wires, distributor and rotor

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droptop73 has a great suggestion. If all the plugs are the same, the issue is something common to all, such as the carb. It is odd the carb would all of a sudden go out of wack.

droptop73, should he check his float to make sure it is working? I never had a float go bad on an original carb, but did seem to have issues with rebuilts.

One other suggestion is the voltage at the coil. BE CAREFUL HERE and check with Pertronix, but I am pretty sure the Pertronix I is a 6 volt system. The voltage at the coil should match Pertronix. If Pertronix is 6V, you should have 6 volts at the coil(measure + side of coil to ground with ignition key on). If you are getting less then what Pertronix says, that might be your issue. If nothing else, it is something easy to check.

Did you really pull off the heads? If so, what do your exhaust valves look like? Maybe you could post a photo.

Did you put the Pertronix Ignitor I in yourself?

How old is it?

This is probably not a factor with your current issue, however, for what it is worth:

1. My understanding is the Ignitor II is more reliable and has better dwell adjustment over the RPM range then the I. I never had the I, but I have about 60K miles on a pair of Ignitor II's. Superb as far as I can tell.

2. droptop73 can confirm/deny this, but I think we would agree the Pertronix I, II and III are NOT high energy ignition systems. They are simply LOW energy electronic replacements for mechanical points. A future modification you might consider(like if/when the Pertronix module malfunctions) would be to go to a Duraspark distributor with an MSD or HEI module(I venture to guess droptop and I would disagree on the module).

Finally, when you do put things back together, do check out the spark. You'll know and hear a good spark when you get one.