Old engine evaluation (M180.924 - ponton)

[rbtoj]

So I have an old 1956 220S engine that is in storage since the early 80's, and I'm thinking of buying an engine-less ponton to use it. But before I go out hunting for an old ponton, I want to make sure that the engine I have is viable.
I'm slowly taking the thing apart and so far the biggest worry I've found is with the camshaft. Three of the cams are quite bad on the backside of the lobe (the lobe itself is fine). One of them has very deep scratches and the other two have lost some of the hard chrome surface finish (again, this is all on the "low" side of the cam. The "high" side is fine).
So my question is: are these bad spots a problem? If so, can they be fixed?

[Sugar Bear]

I don't think it would be a problem if it can be polished and the rocker sliding surface is good. Fortunately it is on the low pressure side of the spring mechanism. If you have to use it keep the valves adjusted frequently and use oil for classic cars/flat tappet camshafts. These are usually C rated / diesel oils and have a higher ZDDP content (yes I'm aware it isn't as high as it was but some are still over 1000PPM ZDDP off the shelf).

There is a used camshaft on eBay now for $450 USD with some good photos that show similar wear to yours except for the scratches. I'd consider polishing the scratches and trying it.

Good luck and keep us updated!!!

[97 SL320]

The dark spots in pic 1 , right of 2 , top of 3 are corrosion. This comes from acids in oil , moisture / lead scavengers in fuel. This last bit is a chemical designed to prevent excessive lead build up in combustion chambers. Problem is, it corrosive and the reason it was common for old engines to stick , fuel tanks to corrode , exhaust systems to fall apart, it is awful stuff. I'm not concerned about the discoloration.

For engines in general, cams are not hard chromed, just thermal hardened.

The marks in pic 3 are mechanical damage not wear marks. Are there slight raised areas around the dents? If not, this likely occurred before the cam was hardened and ground. The dents are mostly only an issue if there is a raised area around them. How does the rocker arm / cam follower look?

[rbtoj]

Thank you both for the replies.

Sugar Bear: at first I was going for a complete engine rebuild, thinking that it was a straight forward engine to rebuild and therefore not too expensive. Boy was I wrong! I looked online for some of the components and I think now I might just make the best with what I got and see what happens before buying parts.

97 SL320: You hit the nail on the head about the nasty additives. This engine stinks like you wouldn't believe! Most of the awful smell comes from the oil.
I have yet to drain it by the way (have to deal with a striped sump bolt first...).

Good to know that the camshaft might be reusable.

Also, upon further inspection I might have an explanation for the "scratches" on the third pic (they do have a slight rise around them, by the way): The adjusting bolt on that follower was pretty much destroyed. So a mechanic might have had quite the struggle, possibly slipping the wrench, and gouging the cam.

I haven't looked at all the cam followers yet, but the couple ones I did looked all right (I'll post more about them later).

I'm posting more pictures of the disassembly process below.

This engine had a hard life by the looks of things...

[rbtoj]

New developments:
The engine has already been machined once, as the pistons are 0.50mm over.
The honing is gone and there is some pitting on the cylinders. I expected that.

Most important though is the fact that piston 1 and 2 have marks indicating they were touching the intake valves, but the other cylinders are fine. I sense trouble ahead...

[Sugar Bear]

The heads hitting the valves hmm...try to find the minimum thickness of the cylinder head. I'm concerned the head was machined too much/thin or hopefully it was a valve timing problem instead. Compare the valve heights also. Are some too long?

Since it has been apart before, do all of the pistons reach the same height to the deck of the block? Are all of the cylinders bored to the first repair size?

Cylinder walls...the vertical scratch doesn't concern me that much. The pitting won't be perfect but it may run well enough with a good deglaze and hone with new rings.

Before going much farther, is it seized? How does the crankshaft look? If the bearings look excellent, measure and reuse them.

You might be ok with rings, a valve grind and seals.We know not perfect but ok.

Good luck!!!

[Stretch]

Whilst I applaud the effort in trying to save old parts (I'm doing similar things myself nearly every day!) I think sometimes you just have to move on.

Turn the block into a coffee table if you must - try selling the parts that look half decent or use them as back up spares to support the purchase of a whole Ponton.

I don't know for sure but I get the feeling that if you'd got this engine back up together and you couldn't find a donor vehicle with out an engine you'd buy one with, swap out the engines and then be back at square one with "an engine that you need to do something with"!

[Tony H]

You will need new pistons since the engine will need to be bored-custom pistons are not too expensive-maybe $150ea. Then you could have the correct compression height and valve pockets cut to compensate for whatever machining was done to the block/head.

[rbtoj]

So I didn't have much time today, but I quickly checked the piston height and on top dead center (when piston 1 and 6 are at the top), I could clearly see a difference in height between the two. I'd say about 0.5mm (I'll have the time to measure things more carefully this weekend).
The thing is, the deck of the engine still has numbers marked all over. You can see some on the pics on previous posts. So I don't believe it has been milled.
I'll have to clean the carbon build up on the head to see if the valves are correct, but from a first inspection they look ok. By the way, this engine had TONS of carbon build up when I first started to take it apart, easily about 1mm on the pistons alone. So maybe this could have caused the valves to impact the pistons?
The head itself looks to be in very good shape as far as corrosion is concerned (see this video => https://youtu.be/qZKFM6gZ3nw ).
Judging by the stamped date on the head, the top might have been milled once though.
Again, I expect to measure it this coming weekend...

As a background story of this engine: My dad is very much into pontons, and had a few during the 70's til very early 90's. So he kept this engine as a spare, but never used it. I always saw it as a potential "coffee table" and nothing else, but recently my dad told me he had many spares for the engine, so I decided to give it a shot. Since he also has many parts for the rest of the car, it could be an opportunity if we ever manage to find an 220s in just the right condition.
He doesn't however have any pistons, valves, valve seals, etc..., but does have main bearings (std size, so probably no bueno for this engine), brand new oil and water pumps, valve guides, two complete gasket sets (but made of the old fiber material), rings and some other minor stuff... ...like a gearbox and replacement syncros... but that's besides the point.

[97 SL320]

Originally Posted by rbtoj

97 SL320: You hit the nail on the head about the nasty additives. This engine stinks like you wouldn't believe! Most of the awful smell comes from the oil.

Just wait until you start removing main bearing bolts. 'Dem dinosaurs have been cooking for a long time.

Originally Posted by rbtoj

Also, upon further inspection I might have an explanation for the "scratches" on the third pic (they do have a slight rise around them, by the way): The adjusting bolt on that follower was pretty much destroyed. So a mechanic might have had quite the struggle, possibly slipping the wrench, and gouging the cam.

Wow, that cam is softer than I was expecting. If you can easily get another cam, I'd replace it. If this engine is only going to see low speeds, light duty, cams are big $$ I'd carefully file the raised bumps flat. Solid lifter / lash adjuster systems have about zero pressure between the cam base circle and rocker / follower. Hydraulic systems put some pressure on the cam so I'd be less inclined to reuse.( but still might )

Originally Posted by rbtoj

This engine had a hard life by the looks of things...

Given the tide mark, I'd say it sat partly filled with liquid. This can be worse than full or empty.

[97 SL320]

Even if you don't rebuild this engine, taking apart stuff and assessing parts is always a good learning experience.

Originally Posted by rbtoj

So I didn't have much time today, but I quickly checked the piston height and on top dead center (when piston 1 and 6 are at the top), I could clearly see a difference in height between the two. I'd say about 0.5mm (I'll have the time to measure things more carefully this weekend).

0.5 mm won't cause this issue nor will milling the head / deck , clearances are not that close. The cylinder block deck / crank center line / connecting rod length / crank stroke might all be off a bit causing a stack up of tolerances.

The valves hitting pistons didn't occur when it was running given it was just 2 cylinders. It was caused by valves that won't fully close due to rusted stems / something wedged under the rocker - follower or adjusting the valve way too tight / then the engine being turned.

Originally Posted by rbtoj

The thing is, the deck of the engine still has numbers marked all over. You can see some on the pics on previous posts. So I don't believe it has been milled.

If the stamped numbers are 1 to 6 down the block, that might have been done during the prior rebuild as there is no reason for the factory to do this. ( If someone knows for sure please post )

However, if the numbers are seemingly random, they correspond to cylinder bore variation from the factory. In the old days, machining was variable so after the bore was honed it was measured. Pistons also varied a bit so large diameter pistons were placed in large diameter bores to keep clearances under control. Sometimes connecting rod and main bearings are sized at the factory, this is a practice that is sometimes done today.

Originally Posted by rbtoj

I'll have to clean the carbon build up on the head to see if the valves are correct, but from a first inspection they look ok. By the way, this engine had TONS of carbon build up when I first started to take it apart, easily about 1mm on the pistons alone. So maybe this could have caused the valves to impact the pistons?

Not enough build up.

[cth350]

If the timing chain slipped, one piston might have gotten messed up before the engine came to a complete stop. That would have bent the valves and precipitated the engine work being done.

Spare heads are around if needed. I know I have one around here someplace. I doubt it still has a cam though. Start by knowing the casting number on the head. From there confirm the head gasket pattern matches up. Also ensure upon assembly that both surfaces are flat, to spec in thickness and that the cam followers are the correct thickness to make the whole thing work right. They come in a bunch of thickenesses for dealing with adjustments.

Also make sure that the rockers are matched to the cam surface. You can't just swap around old parts as they will wear super fast.

-CTH

[rbtoj]

So when I first checked the followers they looked fine, but now after a good cleanup I spotted a slight depression on a few of them. The worst offender is in the pic. The surface still feels very smooth though. Is this what a worn follower looks like? Is it safe to reuse them on their respective cam lobes?

About the numbers that were punched on the block deck, every cylinder is marked with a "1", with the exception of the fourth cylinder that is marked "0".

I'm still eagerly waiting for my mic set to arrive so I can measure the engine...

[jsp300D]

Are these engines still safe with the new gas they introduced? Ethanol is not really friendly on old engines. Otherwise you need to hunt for a OM617 or M110 I guess.

[Sugar Bear]

The follower pictured is worn. Reuse it? Only if you cannot get something better. When something is worn like that it really needs to go back in its original position so it is on the same cam lobe. If you look at newer followers from a side view, you can see how a thin hardened pad/surface is welded over the area where yours is worn.

I'm really interested in the height difference on the pistons...going to guess the two pistons are mismatched to the others from a rebuild (look for part number differences) and make a different compression ratio compared to the others. Also, one of the Pistons that had valve marks was one of the taller ones correct?

You could weigh the pistons and consider removing material from the taller ones if you can make all of them weigh the same when your done. This all depends on what you want from the engine when done and how much time you want to put into it to learn. Clean and inspect the pistons before doing any machining. Check the ring grooves for excessive side clearance, wrist pin bores for too much play and the ring lands for cracks.

The 1 and the 0's were probably bore measurement identifiers for piston fit/selection.

Good luck!!!