With only 10 lbs difference I don't believe that a head gasket is your problem.

 

Those numbers are fine. You don't have a blown head gasket. My service manual says 100 psi is minimum.

 

I have a similar problem with my '98 Ram 1500 with a 5.2l. Changed the plugs and #8 was severely fouled. Checked inside the plenum and it looked clean. I did a compression test and the results don't look too bad,OR DO THEY? I'm only a novice mechanic and I don't know where to go next.

COMPRESSION TEST:

CYLINDER: 1 2 3 4 5 6 7 8
DRY: 175,178,179,179,170,175,170,179
WET: 200,206,205,195,190,195,195,210

 

Remove the TB and look down there with a mirror and flashlight, your plenum is blown and dumping oil on #8 and the cat is getting clogged sending extra heat to the closest place to the cat, the #8 plug.

 

Rusty plug = water in cylinder. Could be a blown head gasket, a cracked head, or a cracked block. Pull the head to discover which, and hope it's just a head gasket.

 

I believe he said "fouled" not rusty.

Sorry UnregisteredUser , My reply was for the thread jacker! LOL

 

No worries, zman17.

It just occurred to me that, logically, "rusted and all junky looking" doesn't necessarily mean the nose of the plug so I should add that my advice applies only if it's the nose of the plug that's rusted.

 

After removing the throttle body the inside of the plenum looked clean. If the gasket is blown on the plenum will it absolutely show signs on the plenum plate, or could it still be leaking onto the # 8 with no signs by looking down the TB?

I understand this is a common problem with my truck, should I just bite the bullet and repair the plenum to see whats going on in there.

What do you think of the compression results?

 

It should show oil just about everywhere.... there is a fair bit of turbulence in the intake manifold...... my JY unit had a nice even film of oil everywhere....... If yours looks pretty clean.... it may or may not be blown, right now.... But, if you still have the steel belly pan, it will fail. Pretty much guaranteed.

If you are getting oil fouling ONLY on the number eight plug, you may just have a blown intake gasket. (manifold to head) Still gotta pull the manifold to fix it, and while you have it off, you might just as well do the plenum fix too......

Wet test brings up pressures a bit more than what I would like to see..... generally, 10-15% is 'acceptable', much more than that, and you are starting to run into ring issues..... most of yours are better than 20%........ Does this mean your engine is toast? Nope. Sure doesn't. Pressures still look pretty good, and are within just a few pounds of each other, if you are not burning an excessive amount of oil, I wouldn't worry over much about that aspect of it, but, you DO need to figger out where the crap on the plug is coming from.

Take off you oil fill cap, leave everything else intact. Start the engine. Put your hand over the oil fill. There should be a LIGHT vacuum. If you are worried that you are going to get sucked in, you have an internal vacuum leak somewhere. If your hand gets blown off, your rings are worse that you thought. (and the numbers would indicate.... don't think that is much of an issue really)