new mahle pistons / rings

[504]

Is anyone familiar with the new Mahle 94mm piston / cylinder set? I am getting ready to install a new set, and need clarification on the ring placement.

I read "put the oil ring gap to the top of the case", but the new oil rings (the ones closest to the base of the piston) seem to have 2 partial gaps, and a red and green marking on them. The red/green markings are not in the center of the gaps (if they are gaps).

I read here that the other 2 rings should have their gaps oriented at 4:00 and 8:00.
I also read in the manual to orient them at 90* from each other, which would put them at 3:00 and 9:00 if the oil ring had a gap and was oriented at 12:00.
Somewhere else I read orient them 120*, which would put the two rings at 4 and 8:00 or 2 and 10:00.

Am I over thinking this?

[bigbore]

[skills@eurocarsplus]

You may want to balance those pistons. They are usually way, way out of wack....like, enough to make your engine have odd vibrations
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[504]

I understand that the 2 compression rings should go roughly opposite each other around 3:00 and 9:00, but what is the deal with the oil ring? I can't see a real gap that goes across the entire ring, does it simply not matter with this type of oil ring?

I haven't weighed the pistons yet, but I am going to before I install them. Can any machine shop balance them if there is a need?

I wonder if Mahle changed their piston/cylinder design, because the ones I'm replacing are 94mm Mahle, and I got around .015 deck height with a .01 cylinder base spacer. I got .02 - .024 on the new ones with no base gasket.

I'm still thinking, can't help that.

[SGKent]

you are basically looking for 120 120 120 spacing with no gaps directly over the thrust areas or piston pins. With a three part oil ring you have to play on that a little with the rail gaps somewhere between 120 and 180 degrees apart. The spring doesn't matter as long as it is equal more or less between rail ends and you can see the red and green.

Do balance them
Do clean them
Do check the gap on them
Do be careful not to cut yourself, rings are like razors sometimes
Do be careful as the cast rings snap easily. My suggestion is put on some work gloves, safety glasses, and find the OLD WORN OUT RINGS. Break them a couple times to get the feel how easy it is to break one. Take a couple old ones on and off an old piston a few times until you are confident you can do it without snapping a new one. Then pull the new ones off and gap them, clean them etc. Use a tool or your two thumbs while you cradle the piston in your hands. Go slow. Put each set in a plastic baggie that is marked. Each piston and ring set has to go back in the same cylinder it came out of as they are individually fitted. You can swap rings around if the gaps are way off. Start with the loosest ones first. My experience with the mahle sets I've gotten from BusDepot is that they are within one gram (excellent) and the gaps are perfect from the factory.
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Canned Water - the new California approved parts cleaner (except in a drought in which case rub it with sand).

George Carlin:
"Most people don't know what they're doing, and a lot of them are really good at it."

Skills@EuroCarsPlus:
"never time to do it right but always time to do it twice"

1971 deluxe (sold)
1977 deluxe

[bigbore]

You forgot Steve make sure the rings are facing up on the piston they are marked if you have three piece oil rings there is no up. .015 is not enough deck unless you have way big head cc's
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where its cold and snowy

[504]

.015 was the deck height on the old p/c's, but the PO used head gaskets so the total deck was about .043

The new ones have .020-.024, I am using AMC heads so with the step the total deck ranges from .049-.053

I found this:
http://www.hastingsmfg.com/ServiceTips/piston.htm
so it looks like the thrust axis is perpendicular to the pin axis?
Therefore I am avoiding placing rings over the pin holes and perpendicular to the pin holes?

[bigbore]

You better cc the heads and do some math to know what compression you will have if you want to run on pump gas because .053 with 94mm and stock cc heads is going to be some high compression.
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where its cold and snowy

[504]

Am I missing something? I get a ratio of about 7.2:1 on the calculator with:
55cc head volume including step
15cc piston dish
94mm bore
71mm stroke
deck height .024 + .029 step = .054

I thought 7.2:1 was a little low

[FNGRUVN]

While we're on the subject....I just bought a set of Mahle pistons & cylinders and the pistons already had rings installed and the pistons installed in the cylinders. I've never had pistons sent to me with rings already installed.

Has anyone else received Mahle pistons this way?
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"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." - Benjamin Franklin

[bigbore]

[bigbore]

[rustbus]

I've read from Jake Raby's site that Mahle stopped making these (cylinders anyhow) themselves and has outsourced to a Chinese manufacturer - despite what the box says, and recently. - so its not unexpected that things seem to be changing with what you guys are seeing.

quality has dropped as a result - inspect closely?
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May of '72 Deluxe. 2.0L L-Jet CS & 091 trans conversion
my Bus thread

[SGKent]

[skills@eurocarsplus]

the chinese AA pistons have been serving some of us quite well... and are almost spot on with the balance


here are the mahle's in my 1904

as you can see, not only was material removed from the pin boss, but also the pin. they were WAY out of wack
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[bigbore]

I just had a customer with a set of AA's and he had a piston come apart I have not tried a set yet not sure if I will at this time.
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where its cold and snowy

[FNGRUVN]