LT Texan

Wouldn't I get traces of gasoline in the oil sample?

M. Requin

Yep, I would think so, which is why I am still puzzled!

69gaugeman

How easy was the short block to turn?

A leak down test would have verified where the compression loss was.

Those marks on the cylinder wall would have reduced compression, but not enough to stop it from running.

Fogey1

I'm still wondering.

I'm puzzled by the abruptness of the way it failed. I once experienced a very quick, over 5-10 miles on an interstate, progressively surging failure that turned out to be the distributor shaft wearing itself to eccentricity. Also, I once had a broken distributor shaft, that was as if I'd turned off the key.

But how to reconcile the abrupt failure with these posts below. How did it rotate when it got down to the shortblock?

I don't think it's diagnosed yet. Cam nose?

Imo000

Take the rings off the pistons you've pulled and lay them down on a white piece of paper. If they are worn down so much that compression is hardly there. You will easily see the wear on the ring thickness.

westija

Sorry to hear about this failure.

It seems from the distance that the wear shown is "adhesive" and not "abrasive" (due to contaminants).
If there are some (heat) discoloration signs at the piston, it is likely adhesive.

If so, it leads me to think that there was either poor lubrication (and agree with previous comments that just the oil type change would likely not cause it) or higher than normal temperature.

As the oil analysis does not indicate fuel in oil, which was one of my suspects, I would think either an oil passage (or some check valve) was blocked somewhere, oil volume was low (not likely) or an overheating caused it.

Crank main bearings are under huge stress, so poor lubrication would have affected them as well, I believe.

westija

One more thing that might help. I looked into the literature about overheating failures and found this too. This is however related to diesel engines (I work in a large diesel engine manufacturer co) , but will work here as well. So, if you get to the valves at some point, you can inspect them for this.

"High Temperature
Valves for engines that operate in an overheated system will typically have a narrow band of oil coking near the bottom area of the valve guides' travel. Mild adhesive and/or abrasive wear may be present. Valves in overheated systems may have deposits of oil coking on the remainder of the valve head and associated parts.
The following items are sometimes associated with high temperatures.
Temper colors.
Adhesive wear
Oil coking
Piston contact"

LT Texan

Today, I checked a few more things.

The crank spins nicely in its journals. Nothing odd there. Haven't broken the griddle apart yet.

I measured the top piston ring gaps for #1 and #5.

Squared up the ring with a piston top.



Then measured the gap.



Got 0.024 and 0.025" on #1 and #5.

So that's 0.6096 and 0.635mm

Spec is 0.2 - .4mm from what I can tell in the WSM.

Not good.

I also checked the crank end play (axial play in WSM?).

I got 0.007" (0.1778mm) with a dial indicator.

Spec is 0.11 - 0.31, so I don't see any problem there.

docmirror

That ring end gap is not what made your engine stop. Continental ran an aviation engine without any compression rings at all and it still made book HP numbers at redline.

So far, you don't have a 'smoking gun' on this deal at all.

LT Texan

The block is an M28/03. 77-79 4.5L 5 speed.

The ring gaps are just a bit tighter half way down the hole.

I guess the out of spec gap wouldn't do much for leak down results, but you'd think they'd build enough compression to fire.

I need to drop off the heads at the machine shop and see what they say.

Still don't know why the engine was dragging so much. Maybe it is the starter, and it really isn't any harder to spin than usual. Maybe I just think it is harder?

Maybe the rings were dragging on the cylinder walls?

69gaugeman

From the pictures there was not enough extra drag to stop the engine. That ring gap is NOT enough to eliminate enough compression to not run.

Wish there was a leak down test as it would have told you EXACTLY where the compression was going.... do I sound like a broken record? ;-)

The reality is there is something else going on that caused your problem. I for one am going to guess the head. Pull the cams and flip it upside down and put alcohol in the combustion chambers. NONE should leak out into the intake or exhaust ports.

LT Texan

Live and learn.

I tried your trick of filling the cc's with alcohol.

Maybe a tiny bit of seepage on exhaust #8. No other signs in other cylinders.

Cams all look good. Spin fine. No broken anything there.

Distributor gear seems fine with the cam spinning.

I am able to compress 5 lifters by hand slightly. That seemed unusual.

Imo000

You can compress 5 litres fairly easily if you go slow.

As for running an engine without any compression ring is a bit hard to swallow. How the hell did they get it to fire let alone to re to redline?

LT Texan

Couple "last" pictures.

The oil pump surface on the block is in pretty bad shape. Don't know if this is new or if this was the way when I put it in, probably the former.



Also, the water pump block surface isn't great.



Time to write this off and rebuild. Move on.

69gaugeman

He said lifters, not cylinders.