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Spark Plug Mysteries

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Webb Sledge

Webb Sledge

Jedi Warrior
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I pulled my plugs again today, and they have me confused as ever. Three of the plugs are dry and black, but have just a little bit of white around the arching piece of metal (don't know the proper name for it) that ultimately grounds the plug. Another one is dry and black on one side, but wet with either oil or gas on the other, and has some sort of deposits (little tiny lumpy pieces) around the insulator. On still another plug, the material surrounding the insulator is peeling/falling off. The insulator itself is not crasked or broken, but the material around it is pretty messed up.

Any ideas on what's causing these things or how to tell whether the one plug is gas or oil?
 
Hey Web,
More info needed. What brand & number plug are you using & what if any ignition components are added.

It would also be good to know how much oil the motor uses in approx 1,000 miles. This is baseline info that will help & may lead to an answer.
also look at this : https://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html
 
[ QUOTE ]
Hey Web,
More info needed.

[/ QUOTE ]Stock or bumped CR? Carburetion?
 
Hi Webb.....
Without knowing a whole lot about your setup, and assuming your compression test (you have done one right?) yields results showing good compression, I would venture to say that it's running rich (most likely) or you've got the wrong heat range on the plugs, it could even mean the ignition timing is out.
A wet plug is suspicious and is probably oil if the wetness doesn't evaporate after a few hours.
If it's oil it might mean valve guide wear assuming the comp test is ok.
 
Weber DGV Carbs, stock CR, and newly rebuilt engine, so compression should be good, though I'll check it soon anyway. I'm on Bosch Platinums right now, though I'm not sure what heat range. It's possible my ignition timing is out, considering the idiots at Vicky Brit didn't put timing marks on my new harmonic balancer, so I had to guess where 0 degrees was. I don't know if it's a sign of ignition timing off, but I usually get a little hesitation when going from light to sudden, heavy throttle loads, unless i'm in 4th gear at highway speeds.

The wetness must be oil though, because I pulled a fouled plug and put it back in the new Bosch's box, and it was still wet on one side several days later.

My car gives me a headache...
 
Hello Webb,

"so I had to guess where 0 degrees was."

I would say you need to mark the new balancer accurately and re-set the ignition timing for a start, then ensure you have the correct heat range plugs. How about timing the cam, how did you set that?

After that then it is a matter of setting up the carburettors, did they come with the correct jets from the supplier? As the engine is freshly built it may use some oil until it beds in but not enough to cause fouling problems.

Alec
 
I had the same problem when I used Bosch Platinums. I changed to NGK's and the problem went away.

The best method I found for setting the timing is to set for a smooth idle, drive the car and slow to 1200-1500 rpm in 4th gear - then WOT - if she bogs = advance , if she pings = retard the timing a bit. I am sure I made several motorists look in awe as I would stop every mile or so, pop the bonnet, loosen the lock nut twist the dizzy a bit, lock it down and drive off. I have the timing marks on my engine, but I don't believe the 4 degree BTDC as stated in the manuals works for every engine. When I finished I was at about 2-3 degrees BTDC. This always has worked for me.
With a newly rebuilt engine, the condition of your plugs indicate you more than likely are just running a bit too rich.
One other thing to check is the charcoal canister(if you still have it in place. If these get stopped up, they can cause too rich of a mixture. [I had "mud-dobbers" build a dirt nest in the vent at the base of the canister (it was amazing how quickly they can do this)and this caused a rich running condition.]
 
Hello Mike,

certainly you have to tune the car by how it runs, but it is much simpler if you have a reference, i.e. timing marks. Start with the base settings and adjust as necessary. Then re-check the timing and you will be able to set to that in the future.
Perhaps those with electronic ignition rarely need to adjust the timing but I'm still on points, and find I need the marks on the damper.

Alec
 
I agree with Mike. I tried Bosche Plat's after I upgraded my ignition sysytem hoping to optimize the new components. I had all negative results. Poor idle, constant fouling & general poor running. I took the advice of a long time TR owner & tuner to stick with Champion. I have been using them pre-blower & with the blower. It has to endure the MSD, hotter coil & the additional pressure of the blower with out a problem. I stil get over 20,000 miles on them before I replace 'em, & I'm sure they could go much longer.

I really don't know the reason for the Platnums poor results in our motors but it could be because of the inability for these cars to run clean. I think they would perform as advertised in cars with engine mangement.

I think you should try a set of standard replacement plugs and do another reading. I would also figure out the proper timing as well.

Let us know what happens. This would be good info for us all.
 
Tr Boost, The MSD6 unit throws such a strong spark it literally blows the platinum off the plug. Platinum is expensive and not much is used there in lies the problem. MSD doesn't include this info in their brochures but if you call a tech they will confirm this.
 
Thanks prb, you would think the current ign systems used today would produce a similar output to the plugs to help run clean & perform well.
It does make sense though, when I removed the Plat's they looked like crap. It keeps the Champs nice and clean with out melting them down prematurly. Needless to say, using the proper heat range is important.

I can say that the MSD will fire a totaly destroyed plug, as long as it has a piece of electrode , it will produce an arc !
 
Hey Webb,
you've already had a number of good suggestions already, but I would ask if the 3 that look ok are all in cylinders fed by the same carb, and the ones you think may have a problem in cylinders fed by the other carb? If so that would seem to indicate a carb related problem, whereas any timing issue affects all six cylinders.

You might try looking very closely at the deposits on the plugs with a magnifying glass and a good light, and comparing with pictures on the net showing different plug conditions. It is very difficult for you to describe plug appearance to us in enough detail to get a good diagnosis.
I am a bit concerned about the two showing peeling and lumpy deposits on the white insulator as this sounds like a lean condition. (Not as bad as tiny bits of silver metal from piston damage due to detonation!)
The slight hesitation may not mean much especially if it happens at low revs in high gear, the mixture likely goes lean momentarily. The Weber DCOE series uses an accelerator pump to provide a shot of gas when you do this, not sure about your DGV's, but as someone suggested it is worth researching the correct pump jet, air correction jet and emulsion tube once you have checked all the easy stuff. Pierce Manifolds may be able to help as they are experts on these carbs.
Good Luck, and let us know the solution, it may help others.
Simon.
 
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