<VV> A Possible Explanation for my galled pistons on my 3.1 - Long

[Bob Gilbert 1]

HI everyone,

 

I have now removed all 6 piston assemblies and each piston showed the same
damage to a greater or lesser extent, more specifically each piston had a ¼
inch wide scratch/scuff from the oil rings down to the bottom of the skirt.
In some cases the oil ring land had been slightly compressed causing the oil
ring to be stuck in the land. There is a very slight scuffing/heat mark on
the cylinder walls which I’m fairly certain I can remove by honing. There is
no other visible damage  to the engine.

 

If anybody wants a picture, I can forward one along.

 

I don’t think we will ever know with 100% certainty what happened but here
is what I THINK may have happened.

 

It started on the last trip – the so-called “trip from hell”. It was a trip
through the Rockies with two adults, the dog and camping gear. The oil
(10-30) was changed right before the trip. About 1 hour into the trip I had
intermittent ignition problems that caused the engine to totally die so as
part of the process of isolating the problem I removed the anti-knock
hardware from the ignition circuit and readjusted the timing by ear. That
didn’t totally fix the problem but the engine never totally died after that.
I drove on for about 5 hours more like that. I drive the UltraVan largely on
the head temperature gauges. Cruising on the flat at 55 MPH indicates 350
and I never let it go above 400 and in most cases I down shift as it
approaches 375 if it’s a long grade ahead.

 

Then , in the middle of the Rockies , far from anywhere and out of cell
range, going up a steep hill I broke two rocker arms (although I didn’t know
that at the time). Having no choice I limped along on 4 cylinders 20 miles
or so to the nearest town where I could use a cell and call a tow truck.

 

Theory A 

What I think was happening was that driving for 5 hours without the
anti-ping technology the engine was probably pinging, at the very least it
was probably pinging under load. Being 20 feet behind me and underneath
thick insulation  and at highway speeds (and me being partly deaf) I didn’t
hear it. This added heat to the motor and stress to the pistons. I found
several references on-line that suggested that pinned connecting rods can
cause piston slap under high load. If so, that slap may have caused the
damage.

 

Theory B

Although I took it easy I did drive a fully loaded UltraVan through the
Rockies for about 20 miles on 4 cylinders. I can’t remember with 100%
certainty  but the broken rockers were on the exhaust side so with the inlet
side still working that might have caused raw gas to enter the cylinders
deleting the oil further exacerbating the problem.

 

Theory C

Some combination of A and B

 

Meanwhile, I’ve ordered new pistons, rings and rods (floating this time) and
I’ll get the cylinders honed to remove the slight scuffing.

 

Regards,

Bob