Carbon build up on plugs- mixture too rich?

[53a1]

Hello Folks. I know this has been covered many times.

I'm reading through all the posts and I just can't determine exactly what is causing the carbon build up on my plugs.

Starts and runs great. Heated up engine and ran at 3000 rpm for a few minutes. I set timing to 5deg BTC, new cooling system is, new plugs Autolite 295 - heat range 5 (same as 2245). New electrical and fuel system. Checked engine vacuum and it's in the good range with tiny fluctuations less than 1 inch-hg at idle. Adjusted carb until it reached max rpm. Has electronic distributor. No smoke, no oil in coolant or vis-versa. Good compression and leak down.

Inspected the plugs and they have a lite coating of carbon buld up. Should I just keep leaning out mixture until it goes away?

Also, it gurgles when I quickly decelerate. Runs a little on the warm side - 190.

Thanks.

[wesk]

Which model engine?

Is it stock? (You mention an electronic distributor?)

Are you driving the jeep at least an hour before inspecting the plugs?

[BullRun]

I would get an older Hanyes or Chilton auto repair book that has a spark plug picture section to compare too for what is "normal" versus a problem.

On some other little auto engines from the '50's a regular "de-coke" was done to remove excess carbon from the combustion chamber.

Fuels have changed so much, especially in the last few years this might just be an unavoidable effect. Just an idea.

The gurgling does not sound right though... maybe the carb is not yet adjusted enough.

If the engine has any significant mileage maybe this is the way it shows itself... hard to say...

[wesk]

There are several simple explanations for the carbon or soot on your plugs but rather than offer you a shot in the dark I prefer to hear your answer to my questions above and then I can tailor comments to your specific application.

[BullRun]

According to my Chilton manual carbon fouling is caused by:

If on one or two plugs possible causes are:
Faulty high tension leads or burnt or sticking valves. The solution is to check the high tension leads for brittleness or cracking causing induction firing, also check each wires resistance with an ohmmeter. If any problems are found replace entire set of wires.

Check for burnt or sticking valves. If anything is found to not be correct evaluate the valve train for adjustment or repair. Also clean and regap the plugs in either case.

If the carbon fouling is on most or all plugs possible causes are:
Overly rich fuel mixture due to a restricted air filter, improper carburetor adjustment, improper choke or heat riser adjustment or heat riser operation. Check fuel system, air filter, heat riser, choke. Further inspection might include the fuel pump (especially output pressure), accelerator pump function in the carb, needle and seat or float problems within the carb.

For anyone not familiar with Chilton manuals they offer basic repair and diagnostic run down sheets for cars and trucks and have been around for decades. They used to be found in professional and amateur garages alike for a "quick" reference if you did not have factory manuals.

Beyond that it is hard to be anymore specific without more details.

[53a1]

Thanks for the replies.

Wes, I didn't run it for very long maybe 10 minutes and it's an F134. I'm not in a situation where I can drive it for that long because the tub is not installed.

I acquired an Omix electronic distributor in a parts deal so I put that in to eliminate points for the time being. It actually runs real smooth with this distributor but it's not stock.

Thanks.

[wesk]

Then the soot or carbon is really not an issue. Using spark plugs to gauge engine performance when the engine appears to run just fine is not very accurate without at least an hour's running time. I doubt you have any mixture issues. Enjoy the rest of the project and re-evaluate when you can run it long enough to make an accurate assessment.

As for manuals I would strongly suggest you first obtain the M38A1 specific manuals then when you have spare change and wish to have a simpler read around the shop you can consider the Chilton type manuals which are not very vehicle specific nor do they offer any great insight into heavy repairs but they are written in a way that helps the novice better understand some principals.

[maeserik]

When your jeep is finished and you drive about a 20 or more miles with a speed above 4O mph you will find out that the plugs will be clean. Your engine just needs a few hours driving on normal working temperature.
I already have my jeep restored for about 5 years, and i still use the same plugs ( about 7000 miles used ). But in winter and after a short trip, just to warm up the engine and charge the batteries, the plugs become black !

When you have a smooth running engine and power enough you do not have to worry.

Erik