Inherited a 96 Dodge RAM 5.2L with 174K, what oil?

[rslifkin]

^ Correct. They tend to be hard on oil if run with a blown plenum, but even then, it's not a sludge problem per se. It's more like bits of hard carbon that end up blocking the oil pump pickup. If the plenum is good, they'll stay pretty clean. When I had the intake off mine shortly after I got it (first 99k of its life was on bulk dino at 3k), it had light varnish, but not a hint of sludge.

 

[440Magnum]

Originally Posted By: rslifkin
^ Correct. They tend to be hard on oil if run with a blown plenum, but even then, it's not a sludge problem per se. It's more like bits of hard carbon that end up blocking the oil pump pickup.


EXACTLY! I'd like to know exactly what the process that forms all the carbon-like grit actually is. Fuel dilution from fuel getting into the crankcase? Exhaust leaking from EGR passages? Just added heat from the detonation due to oil getting into the combustion chambers? Whatever the process is, it results in remarkably uniform-sized pieces of grit. You'd expect some tiny bits and some large chunks if it was just random, but its very uniform. At least in my observation.

And its *definitely* a result of the plenum gasket failure, because the old TBI and carbureted LA engines and Magnum LA engines retrofitted with the Mopar Performance R/T intake/exhaust package don't do this.

 

[rslifkin]

I've got no idea what causes it. Your guess about extra heat is probably about right. Maybe it's carbon buildup occurring in the rings and then breaking free? It could be causing some fuel dilution as well, as it puts the crankcase under a good bit of extra vacuum, which will pull more [censored] past the rings (which also goes with the rings creating the carbon bits theory).

 

[SteveSRT8]

Vacuum is over the rings, not under. That's the PCV's job to regulate.

In the 70's and early 80's we owned many dodge vans. Most were 350 models so they had 360's but we had 318's as well.

All of these vans usually ran well for 150-200k miles and then stripped the timing gear(s). Most of them we simply put new heads, timing set, and an oil pump on and drove them many more miles trouble free.

The oil pump pickups were always full of timing gear bits and carbon. Many times they were nearly blocked.

Since every piston I ever took out was heavily coked up in the grooves I'm sure that must be where the carbon comes from.

 

[440Magnum]

Originally Posted By: SteveSRT8
Vacuum is over the rings, not under. That's the PCV's job to regulate.



Yes, but he is talking about when the lower intake plenum gasket fails. in that case, there's a big honkin' vacuum leak *inside* the crankcase. There's also reversion of fuel-laden intake air into the crankcase under some circumstances, too, so its just a really ugly failure to have happen.

If it is coking up the rings and breaking free, that would explain the relatively uniform grain size. but unlike you, I've never (or I should say RARELY) seen this in a pre-Magnum version of the engine.