In the next post are 2 shots of my sparks with about 800 miles on them, Autolite PP104s. They are cylinders 1-6 from left to right.
3 and 5 show a lot of sooting on the threads so I've been replacing these two sparks every month.

Compression test showed 3 and 5 are low (85/90) but a wet test brings them both back to 150, so I thought rings but
the truck burns almost no oil and oil is still goldish brown and clean after 1500 miles - only down about a cup
Engine passes head gasket test- started cold, topped up with AF, vent cap off, return removed.

So it seems like rings except the oil looks good, no smoke out exhaust, not burning oil.

I'm changing sparks because after 30 days she gets hard to start and runs rough. I run 104PP but am experimenting with 104 copper tips starting today just to save a buck since I have to change them out regularly.
I guess I'll start slathering some anti seize on the spark threads thick because I'm wondering if I have a good seal in the spark sockets.

Anyone else have this kinda soot on plugs?

 

 

Whats the MPG like?


Yes, 3 and 5 look to be burning oil or unburn fuel, misfiring can show the same carbon/blackish build up as oil burning
Leak down may be only test to tell you if its rings or exhaust valve leaking at this point, WET test did indicate rings but might not be definitive

The low compression WOULD cause misfires so unburned fuel coating in cylinders

Wouldn't worry about the "soot" on threads at this time

Whats your gap?
0.045" was spec for 3.0l Vulcan in all years

 

That's good info Ron- I've been gapping at .050 -55 forget where I got that info, online somewhere. I'll re-gap them in the morning. Leak down kits are cheap- $29 Amazon but I'll see if I can loan one at a parts store.

Curious- if I'm blowing thru plugs bc they are fouling should be fine to just use cheap coppers - right? They are $1 vs. $5 for the Plats

 

Yes, no coating(copper) is fine to use

On Rangers with no distributor you should only use copper or Double Platinum, signal platinum is a waste of money, just FYI

Any spark plugs you buy for the 3.0l Vulcan should be pre--gapped to 0.044"-0.046"

The 4.0l OHV used 0.054"