New Mahle P's and C's - best prep?

500_19B · 03-14-2012, 08:45 AM

I have a set of brand-new Mahle P’s & C’s for my 3.2 re-build. Mahle supplies the pistons with the rings mounted and in the cylinder (see pic):

I have to remove the piston in order to clean everything and align the ring gaps. My question is whether to remove the rings for the cleaning process?

My instinct is to leave the rings in and clean the piston and rings as an integrated unit, as this minimizes the chances of ring damage and/or incorrect re-installation orientation.

What do others think?

Thank you taking a look,
Allan

Eagledriver · 03-14-2012, 09:59 AM

I would leave them on the pistons except for one piston. Take them off one piston and check the end gaps for fit. They look nice by the way.

-Andy

Flat6pac · 03-14-2012, 10:58 AM

Dont worry about the lne up, they will move to their own orientation.
Brucei

500_19B · 03-15-2012, 07:24 AM

Hmm... Good point, I hadn't thought about ring gap measurement, thanks!

Hey Bruce, that is an interesting observation about ring gap alignment. Is it possible that Mahle packed the P's & C's this way with the intention that they would NOT be disassembled prior to installation? It seems like a lot of effort for them to pack them this way...

Again, thank you both for your informative feedback!

Two Rivers · 03-15-2012, 07:37 AM

Flat6pack. So what you are saying is to ignore what Porsche says about ring orientation and just throw the rings on randomly spaced. And they will magically space them-selfs to the factory orientation?

Every engine I have ever rebuilt has had a ring gap spacing specification.

930LDR · 03-15-2012, 08:48 AM

I bought new P&Cs for my 930 from Mahle and removed each piston to make sure there weren't any cracks in the rings. Would be a real bummer to have found out after the fact that there was one.

jeff eelkema · 03-15-2012, 08:23 PM

Would it be reasonable to assume that the manufacturer of the pistons and cylinders would check end gap prior to delivery and that they would set ring spacing to their specs? There is always a chance that someone at the factory gets something wrong, but there is probably more risk of a DIY mechanic breaking a ring getting it back into the bore.

Flat6pac · 03-16-2012, 05:30 AM

If the rings didnt move then every piston should have the 120 degrees between endgaps when theyre removed. I ve built enough engines to know I orientate the rings. The couple I ve opened on short run time, the rings have always moved to their own alignment.
Bruce

nocarrier · 03-16-2012, 07:42 AM

I just prepped a brand new set just recently.

I removed all the pistons and rings. Cleaned the cylinders with very hot water and dawn dish soap. Dired quickly with a dust free cloth and alcohol and lightly coated with clean oil.

I checked all the ring gaps, measured the piston and pin weights. I made notes of each set of gaps for each ring.

Everyone of them were exactly the same by measurement of my feeler gauge.

On the rings, the factory applied some sort of oil or rust preventative to the rings.

On a couple of the rings, I found that some of this "substance" appeared to have "dried out" leaving behind a much thicker than grease residue on some of the rings.

I had to use my fingernail to remove it.

I cleaned each and every ring with a dust free cloth and alcohol. Re-assembled them on the pistons and they are waiting to be assembled on the motor.

I am going to set the ring gaps in the correct locations with the oil control gap facing up.

I have to admit.......this is my first Porsche engine that I am building, but with my experience in the past with other engines. I don't like to leave things to chance. Especially cleaning new or newly machined cylinders.

500_19B · 03-16-2012, 09:33 AM

Great feedback everyone, thanks!

I will align the ring gaps upon re-assembly in the normal pattern, even though, as Bruce points out, they are likely to migrate from there. May as well at least start in the right orientation.

Ronnie's.930 · 03-16-2012, 08:54 PM

Quote:

Originally Posted by Flat6pac

If the rings didnt move then every piston should have the 120 degrees between endgaps when theyre removed. I ve built enough engines to know I orientate the rings. The couple I ve opened on short run time, the rings have always moved to their own alignment.
Bruce

This has been my experience as well. I'm not sure why engine manuals bother to state ring gap orientations as the rings freely move about when the engine is in use!