Zero10

Well, I'm still on the hunt for some 100.5mm pistons. I've had a couple maybes, and then I got the brilliant idea to call up Sunset Porsche.
They quoted me around $240/piston for 100.5 tolerance group 0 pistons, however they are no longer available.
They can get tolerance group 1 pistons, but they're pushing $400 each.
I'm hoping for some insight on what to do here. Does anybody know if there are 100.5 group 0 pistons around?
Or is the price on group 0 pistons so low because they've been discontinued for so long?

I'm hoping to find a drop-in piston solution, where I won't have to worry about coatings flaking off or anything like that. I plan to put this motor together, and never have to open it up again.

Could I get a set of N/A 100.5's, and dish the hell out of them?

84black944

I beleive hosrom sells pistons did you ask him yet?

Zero10

Yep, he can only get 100mm 951 pistons. Does anybody maybe have a used set of 100.5mm 951 pistons?...

OriginalSterm

Possibly!

If you are still looking in a week or so, I will know for sure.

Ski

You know you've been having this conversation for sometime now.

Tom C for $1125, Mahle 100.5 $1695. I have a set of 101mm that were bought last year. I don't need them right now, $1000 + ship.

Zero10

I have been having this conversation for some time now, I wish the answer was really clear cut, then this conversation would be much shorter, and more definitive.
Sunset porsche is cheaper than the Mahle price you are posting, at around $1580/4 pistons.
I can't recall what brand the 101mm pistons were, and if they were coated, what with?

dand86951

What is the difference between tolerance group 1 and group 0? Porsche allows a fairly broad range of piston to wall clearance, even though new spec is quite tight, and depending on your bore and group 1 pistons sizes maybe you can have Precise run the hone through once or twice to get the clearance you need. That would be an extra $600 or so, but would be drop in with factory parts.

Dal Heger

The difference between the tolerance groups is 0.05mm. Yes the piston to cylinder wall tolerances are that close.

For my money, I'd get the 101mm Porsche pistons and match the cylinders to the pistons. The difference between the mahle pistons and the Tom C pistons is not that high.

Dal.

Zero10

I wish. I have to bore out over 0.1mm all around, so I would need pistons of at least 100.2mm. IIRC, the max piston-to-wall clearance is something like 0.08mm, which they consider the wear limit. The wear limit is set so that they don't have to replace too many engines under warranty, so their wear limit is much past mine...
Considered coating mine to make them bigger, but that's just asking for them to flake...


Ski, what brand are the 101mm pistons, and what (if any) is the coating on them?

H2Opumpr

I coated mine( if your looking for alternatives) but I wasnt looking for perfection. Havnt had a problem yet, but who knows about the future....... I put 3000 miles a year on my car, and at that rate It'll take me a long time to wear it out again.
The question is how tapered are the bores, that exacerbates the wear in an inaccurate pattern which of course you dont want. Mine were barely tapered so I just coated and I have 150 psi on all cylinders, and dont burn any oil(relatively). If yours are fairly true, then try to coat, its pretty cheap. If it doesnt work, back to square one...you lose some money on gaskets and time. BTW, EBS does great headwork and very professional if you havnt researched that yet.

Just weigh the options, you dont always have to drop for the big ticket. Just my 0.02$

Ski

The pistons are the Arias that Tom C got going. They are coated with an iron/graphite coating. We have them in the track car and very pleased so far. Jim did an engine last month with the same pistons in 100.5, the owner has put almost 4 miles on her, doing fine. You can see them if copy and paste the JAB link in the sig. I think they're on page 4.

Zero10

I forgot to mention the taper....
0.1mm scratches, 0.15mm taper.
Boring 100.5 will just barely take care of the damage

I have a potential line on some original factory 100.5mm used pistons, but they need the side skirts recoated, but the price pretty reasonable. If they don't come together, I'm definately interested in your set.

Stupid question, but it looks like the block they went into was sleeved?
Will these pistons be compatible with alusil bores?
You mentioned that you weren't using them, how many miles do they have on them, and how are they holding up coating-wise?

Thanks,

Ski

No sleeves, just great machine and alusil work by Duffin Engine in San Antonio TX! He has two blocks of ours at the moment, they should be finished on Thursday. One going to 100.5 the other going to 101 for 2.8L stroker, Duffin does excellent work.

Zero10

Stupid question time, if I were looking at a 100.5mm piston, how could I tell if it was a Mahle piston, or what coating is on it?
I have a potential line on some pistons, that say 'SKF', and '100.48' on them. The only 100.48mm pistons I have ever heard of are factory pistons, everything else is 100.50.

Ski

well, 100mm pistons are 99.97-99.99. The factory iron coating is gray looking. Most of the Mahle have a KS stamped on them for Kloberschmidt (sp?)