Low compression

[Malcolm Towrie]

Lynn, I should have got into the ignition problem in a separate thread to avoid confusion as it was a totally separate problem. The low compression hasn't gone away!

That shaft wouldn't bend in service but throwing it in a box and then throwing other parts on top of it would bend it easily, based on how easily I straightened it.

Malcolm

[Malcolm Towrie]

An update: due to the low compression test pressures reported at the beginning of this thread, we just pulled the engine to find the cause. I've only got the heads and intake manifold off so far, but checking each valve when fully open, I can see damage to the exhaust valve seats of the 4 low pressure cylinders. That seems to be the culprit. The other exhaust valve seats look ok, so I'm not sure why these particular seats went bad. Tappet clearance too tight and holding the valves off the seat perhaps?
The cylinders are 0.015" over and a bore gauge check of the bores just above the pistons at BDC and at the TDC wear "ridge" shows wear in the 0.002 to 0.003" range for all cylinders, so acceptable, IMO. But even the 4 "good" cylinders only had 85 to 95 psi results instead of 110 psi, so I think the bores need honed and new rings installed.
The valley shows a depressing amount of sludge on all surfaces. And the oil pan has a good layer of black sludge on the bottom. We use a 15W40 diesel oil in most of our vehicles. This is a high detergent oil and I suspect it is bad news in this type of application as the detergent dissolves the stable sludge deposits and circulates it around the engine. We should be using a non-detergent oil on these old engines.
I also found a water pump with the bearings almost seized, front crank seal rope packing installed so tight, it had burnt the paint on the timing cover, causing a severely scored front pulley sleeve, and a crack in the block around the rear boss for the oil cooler supply, due to overtightening the fitting. I'm not sure how to repair that. All in all, a typical 75 year old engine.
Malcolm

[Lynn Eades]

Malcolm, What model is the engine? What casting numbers if any? Does it have domed pistons? What cylinder heads does it have? What bore size? (just checking)

[Malcolm Towrie]

Originally Posted by Lynn Eades

Malcolm, What model is the engine? What casting numbers if any? Does it have domed pistons? What cylinder heads does it have? What bore size? (just checking)

Lynn, yes, it has domed pistons. CR is 6.12:1.
Stock bore size is 3 1/16", 3.0625". This one is 0.015" over so 3.0775".
It's the 85 HP, 221 cu. in engine. I'll get some casting numbers.

Malcolm

[Malcolm Towrie]

100% agree with you, Richard. Ever since seeing fresh Shell Rotella T 15w40 (a very popular diesel oil loaded with detergent) turn black within a few miles on one of our Ferrets, I've had my doubts about the wisdom of using this oil in our old engines.

And since then, I've seen how much sludge accumulates in the oil pans of these old engines. In fact, I suspect the oil pans were made so deep just to provide a nice quiet place for particulates, varnishes, etc. to settle down into out of the way to somewhat compensate for the lack of filtering. Dissolving this stuff back into a high detergent oil is bad news.

Malcolm

[Jim Burrill]

HD oil issues - My Humber Mk4 Armoured car had an engine rebuild at the shop in the UK. With less that 50 hours of run time, we burned up no4 Main bearing.

The final understanding was that during the engine rebuild, two oil channels (which has a freeze plug type cap on one end, and a bolt on the other) was not opened and cleaned out.

We put HD oil in for our running in.

Apparently, it dissolved the sludge and circulated it to the oil sump/pan. The pick-up for the oil pump has a metal wire filter. That was completely sludged over. The resulting oil starvation caused #4 piston main bearing - a poured babbet bearing - to melt.

We had a machine shop remove all the babbet bearings and switched to cap bearings.

We are better off having cleaned the oil journals, but some $4,000 poorer for having to pull the engine and the rebuild.

So.... no more HD oil for my stuff!

[Malcolm Towrie]

Jim, based on a similar bad experience I had, I'd be more inclined to blame the shop than the oil.
I had a local shop do machining on a Chevy engine. As normal, they hot-tanked the engine first. But, like your shop, they didn't remove all the gallery plugs and flush/brush the galleries out. Luckily I noticed when I got it back. I removed the plugs and found a large amount of sludge behind them that had been softened to a semi-liquid by the caustic cleaning solution. I shudder to think what that stuff would have done to the new bearings as soon as the oil started circulating.

Malcolm

[Malcolm Towrie]

Originally Posted by Malcolm Towrie

Lynn, yes, it has domed pistons. CR is 6.12:1.
Stock bore size is 3 1/16", 3.0625". This one is 0.015" over so 3.0775".
It's the 85 HP, 221 cu. in engine. I'll get some casting numbers.

Malcolm

Lynn, I couldn't find any casting numbers, strangely enough. This is a 24 head-stud engine.

[Michael R.]

On Canadian produced engine blocks found in universal carriers MK-I* and MK-II*, the engine block casting number is displayed on the shoulder over the water pump. Viewing from the front of the block, the 'left side'. The number '81' casting plate may appear as '87'. (see image of two examples)

Serial numbers on Canadian produced engine blocks found in universal carriers MK-I* and MK-II*, the number being displayed on the exposed portion of the intake manifold deck. Viewing from the front of the block, the 'right side, rear corner'.

Serial number format is 'TLXXXXXF'. There may be multiple 'F' letter strikes after the normal sequence, as well as the inspector stamp and additional letters or symbols, the more common upper case letters being 'E' and 'V'.

The complete serial number example displayed belongs to the engine found in the restoration thread for the carrier in Israel, with thanks to Mr. Berko. Of note, that is a MK-I* carrier, upgraded to MK-II in the UK and given a British cast data plate, with a MK-II* engine block.

See: http://mapleleafup.net/forums/showpo...7&postcount=70

[Malcolm Towrie]

Thanks, Michael. I found the "81" but only because you told me where to look. The cast number is almost illegible.
I didn't find a serial number of any kind. I did find a brass plate identifying a rebuild by RCEME in 1951.

I've got 9 valve/guide assemblies out and two pistons so far. Everything looks in good condition.

Malcolm

[Richard Farrant]

Originally Posted by Malcolm Towrie

The valley shows a depressing amount of sludge on all surfaces. And the oil pan has a good layer of black sludge on the bottom. We use a 15W40 diesel oil in most of our vehicles. This is a high detergent oil and I suspect it is bad news in this type of application as the detergent dissolves the stable sludge deposits and circulates it around the engine. We should be using a non-detergent oil on these old engines.

Hi Malcolm,
A mistake people often make is getting an old vehicle of unknown history, draining the oil and refilling with a detergent multigrade oil. Most of these old WW2 era engines (and earlier) had either no filter at all or a bypass filter, which was tapped of the oil gallery and returned to sump. Detergent oils keep dirt and carbon in suspension so with a full flow filter system it is quickly cleaned. The older mono-grade oils had no detergent in them and the sludge formed in the sump mainly, so it was flushed out on oil changes. If you get hold of an unknown engine and it has a bypass filter, or none at all, go for a non-detergent mono-grade as blended for vintage vehicles. Actually the Classic / Vintage mono-grades in the UK do now have a very slight detergency in them as I am informed by the oil companies, but they do not scour out all the old sludge like a multigrade does.
Hope I am not teaching you to suck eggs, but I am sure there will be readers who are not aware.
regards,
Richard