Opinions on these 603 pistons
 

I got the head pulled on the 603 this afternoon. How do these pistons look? I realize they will need to be measured to determine if they are good for sure. But generally speaking what kind of condition would theses pistons be considered in?

I cleaned up one to get a better look at.

Can pistons be refurbished?

Cheers, Allen

The original machining on the skirts still looks present at least. Do you still see the cross hatching on the cylinders?

The pistons will have to be measured of course. Mark each piston to the cylinder it was extracted from. Are you thinking new cylinder liners?

Probably just a lighting/shadow issue? If not you may have too much wear in the ring lands. The quality of reproduction of your photos will vary to many members on their monitors. Mine may be worse of better than average.

.Just a guess by me but those pistons appear to be worth checking out further. The scuffing I noticed at the top of the piston above the compression ring. Does indicate some contact was occurring.

Another option depending on many factors. Is obtaining a really good used engine. If I found one still in a car. I would run it and do a compression check. It never fails to amaze me just how many of the old Mercedes diesel engines are still about the same as when new compression wise.

The frugal way is to find another car with a really solid engine with an updated head. That has so many other issues it can be purchased for very little. Depending on your space available etc. You just might recover enough by selling surplus parts to recover your acquisition cost as well.

Bottom end issues on the 603 three liter engines are almost unknown. Especially for engines this old. Unless seriously overheated taking some temper out of the rings or the oil was seldom ever changed. I rate the short block as really durable. Yet having a problamatic head with the original number 14 one . For example if you could pick up a complete good engine that had an updated head on it reasonable enough you might be well ahead of the curve.

A lot of availability again depends on your location. I do feel personally that an original number 14 head is not even worth rebuilding. Unfortunatly the upgraded ones are expensive usually when sold already off the engine. So my methology would be the most likely way to get one cheaper with a good short block sitting under it as a bonus.

As I used to tell the ladies. I may be cheap but I am also easy. At times I can squeeze the dollar so hard it screams for mercy. A remaining habit left over from our earlier days together.

Measuring is the only way to tell if they are still good. You will need to measure skirt diameter, ring land height, pin diameter.

A piston can have machine marks visible on the skirt but it could of collapsed over time / overheating.

you can't tell anything without measuring. It's not the correct way to do it, but if the motor wasn't severely overheated or run low on oil I'd just throw rings on it and put it back. As long as it doesn't have over 350k miles on it otherwise I'd measure it.

When I saw the scuff marks above the compression ring. I thought a reduction in skirt diameter might be a cause. Or bore wear. The other thought was perhaps the compression ring had lost too much temper. Many 603s have had overheating episodes in their past. Measuring provides answers.

The cost of new parts is just so high. When dealing with these engines internal needs.. This can seriously impact choices in many ways.

I live on Big Island Hawaii, so choices are a bit more limited. I’ll look around for a clunker car with a #22 head from being updated. Who knows might get lucky.
Since I’m not in a hurry to have the engine built and going, I have time to look for one.

If worse case for pistons and need to get new ones, are there pistons made by same company that makes them for Mercedes, but not in Mercedes box?
Who makes them of equal quality as Mercedes ones?
Who sells them, I tried to find dealers on line, but didn’t have success.

Cheers, Allen

The scuff marks are probably from carbon at the top of the bore. If the skirts are worn to the point they allow the piston top to hit the bore, they are really worn out.

Given your location, you need to contact the guy that started this thread, he may have some parts connections.


http://www.peachparts.com/shopforum/vintage-mercedes/378762-69-230-build-w-lq4-swap.html

My understanding is that the critical measurement is with a feeler gage between cylinder wall and piston skirt on the lower side. Ideally, one hones each cylinder to fit the piston intended for it. Typically, one over-bores a cylinder for larger pistons, such as old U.S. V-8's. But, I haven't heard of over-sized pistons for these old M-B diesels. Instead, new cylinder liners are installed and honed to size. If not doing that, the best you can do is hone just enough to resurface the cylinder walls and fit new rings. I would re-use the existing pistons since they look fine, though non-turbo pistons are not exorbitant in price like turbo pistons are. Worst-case would be that you hear "piston slap" from the skirts hitting the walls. If you weren't hearing that before, I doubt you would after a re-ring.

there are some aftermarket products but those are low quality products,original was and still is made by Nural.

-- shameless plug - search my old posts and you can find some parts suitable for you....


cheers

ChO


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Will be getting new set of Mahle 87.5mm pistons & rings from Fred at F-Tune Performance in Sweden. mercedes.f-tune.se
They are about $1050 for set of six with rings. I say about, because the exchange rate can vary a little bit.

By being.5mm oversize, gives enough to clean up cylinders for like new fit & finish.
Will be getting all the bearings, seals, valve springs & other bits & pieces plus injectors
rebuilt by Fred.

Getting the pump rebuilt and 7.5mm elements in it, custom exhaust manifold and hybrid k14 fast spool turbo from Diesel Pump UK.
This is going in my Alan’s Rover 69’ Series SIIA 100” I’m building.

I have a FB page about the build at, facebook.com/69Series2A/

Cheers, Allen

Did you contact the guy in my post 9 ?

97 SL320, no I haven’t yet, I missed your post somehow. I will contact him now that I have seen your post & recommendation. Thx.
Cheers, Allen