Oil buildup on spark plug

[tino0217]

About a year ago on my 71 C10 I know the truck was missing when I drive when I check the spark plugs on the driver side first plug towards the front there was oil deposit and build up which was making the truck miss. I had a leak in my oil pan I had somebody come out and change it and the valve covers now in the last week the truck was missing again so I checked the plugs thinking it was that same one but it wasn't I checked the passenger side plugs and it was a third one back that had oil buildup on it which is making the truck Miss anybody have any ideas why this happened

[AussieinNC]

This sounds like a tired engine giving you signs of wear....

Are you sure its oil?

If a plug lead dies, the plug will not fire and will build up unburnt combustion mix and oil bypass from guides and rings etc. will show as an oily mix.

Suggest the following in order:

1/ Remove all plugs and perform a compression test, list the results in each bank so we can see cylinder readings against the adjacent cylinders. As an FYI...
drivers side cylinders front to back are numbered 1,3,5 and 7
passenger side cylinders front to back are numbered 2.4.6.and 8

2/ Lay out the removed plugs in each bank order, and post a pic of each bank showing the chamber electrodes.

3/ Check each plug lead for physical damage due to contacting exhaust manifolds or pipes. Replace any damaged ones...if more than 3 or 4 are damaged or suspect, suggest you replace all leads...but before buying new ones post compression results....

Post the results and we can help ya out...once we see the pics and readings etc.

[Wrenchbender Ret]

If you have an auto trans. pull the hose off the modulator & see if any fluid is in it. A leaking modulator can deposit oil on specific cyls.
George

[AussieinNC]

Originally Posted by Wrenchbender Ret

If you have an auto trans. pull the hose off the modulator & see if any fluid is in it. A leaking modulator can deposit oil on specific cyls.
George

Good point Sir...

Leaking vac mods usually cause lots of blue smoke out the pipes....and usually affect cylinders 7 or 8 due to location of vac port in rear manifold ports....

[cleszkie]

A lot of blow-by getting pulled into the carb through the PCV valve will also manifest itself on specific cylinders depending on which cylinders are fed by the intake manifold runners that pass closest to the PCV port in the base of the carb.

The same thing will happen if you don't have oil baffles installed in your valve covers at the PCV valve port. Oil will get sucked into the PCV valve and deposited into your carb, affecting only specific cylinders as explained above. Ask me how I know!

[burnin oil]

Lots of good input here on possible problems. If money is limited or you just want to keep it running you can try adding a set of hotter plugs. Just go up one heat range to help keep them clean. It wont fix any wear issues but will help keep it running.

[tino0217]

Before I post the results I was looking at the distributor cap and there was a few of the plugs wires that were very loose no resistance when pulling them I did do the compression test these are the results but now I have a real headache the timing has gone out

[Grumpy old man]

Those plugs look great clean re gap them and reinstall and timing doesn't change by itself , Maybe by accident the wires are mis installed , firing order is 18436572 how much do you drive it ?

[tino0217]

It's my daily. I drive it as much as i can, any excuse will do...lol. I had it running but it was backfiring so moved the distributor and it got better but idled high. I started over and redid the firing order and found a distributor cap with brass connections but now the batteries dead. I'll go get it charged in the morning. Wish me luck