Plug fouling

1952 - 1968, M38A1, M170, questions, discussions, regarding anything related to the M38a1 series.
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Michael Keller
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Plug fouling

Post by Michael Keller » Tue Jun 14, 2016 3:21 am

I'm getting oil fouling on one plug. Is a hotter plug available for the M38A1 that would be an easier solution than replacing the rings?
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Joe Gopan
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Re: Plug fouling

Post by Joe Gopan » Tue Jun 14, 2016 4:01 am

You could go to Auto Lite 2247, Champion XMJ-20, These are the same reach as 2245 Spark Plug but I doubt that is the cure. First impression, I would rather suspect a Valve Seal on that cylinder that is allowing oil to get by. When the seals fail, the M-38A1 gets Oil Thirsty. Best do some tests as it may be wear in that one cylinder.
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Michael Keller
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Re: Plug fouling

Post by Michael Keller » Tue Jun 14, 2016 1:15 pm

I got over being lazy and started tearing the engine down today. I'll replace the rings and whatever else is boogered, incuding the valve seals. About the only thing I haven't overhauled on this motor so far are the rings. 'Might as well get it done right.
1943 M15A1 Autocar halftrack (restored)
1941 Chevy dump truck (restored and sold)
1978 M416A1 Quarter Ton Trailer (for sale)

Joe Gopan
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Re: Plug fouling

Post by Joe Gopan » Tue Jun 14, 2016 1:21 pm

Sounds like you want it fixed, good idea.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
7 MIL SPEC MAINTAINED MV'S
COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO

Michael Keller
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Re: Plug fouling

Post by Michael Keller » Sun Jun 19, 2016 3:59 am

Anybody know the torque spec on the head bolts?

Is there a torque spec for the crank nuts?
1943 M15A1 Autocar halftrack (restored)
1941 Chevy dump truck (restored and sold)
1978 M416A1 Quarter Ton Trailer (for sale)

Joe Gopan
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Re: Plug fouling

Post by Joe Gopan » Sun Jun 19, 2016 4:47 am

Torque spec for M-38A1 Cylinder Head Bolts is 60-65 Ft Lb. I have never found a Willys spec. for the Pulley Nut, you will notice that the direction of rotation of the engine is counter to that of the direction to tighten the nut.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
7 MIL SPEC MAINTAINED MV'S
COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO

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Re: Plug fouling

Post by artificer » Sun Jun 19, 2016 10:57 am

Would have been a better idea to do some testing & finding out what actually needed repair.
What were the dry & wet compression readings?
Rings are usually poor on all cylinders, not just one, unless someone has done a dodgy job previously.
Inlet valve stem oil seals on one cylinder is a very real possibility from what we have been told & these can be easily replaced without removing the cylinder head.
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Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.


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