Help Identifying Early 911 Pistons

[Hcarraro]

Hello everyone,

I need your eagle eyes and your years of Porsche engine building experience to help me identify these NOS pistons.

Here is what I know. They are 87.5mm in diameter and don't have any manufacturers markings such as KS or Mahle that I can find. There is a P8800 cast into the cavity as well as the number 2.12 which is also cast in the cavity. On the top of the pistion, there are two distinct "STD" markings. One is stamped in the metal and the other appears to be an ink stamp.

I received an email yesterday from a fellow who saw my ad for these pistons on Samba and said he had an identical set he removed recently from a 1966 Porsche 911 and was wondering if I knew the manufacturer. I told him unfortunately I did not but I would post this request for help on Pelican.

Jamie Novak said he thought they might be for a 2.5 liter 911T Rally motor but he was concerned with the unusual ring groove below the wrist pin. A friend of mine last night said the Porsche 356 pistons had a similar ring groove below the wrist pin as well.

Let me know what you think. Thanks in advance for your help.

Henry
hcarraro@hughes.net

[BURN-BROS]

Looks more like Ferrari or Alfa stuff. The are cast and definitely not a racing piston, more a performance street thing.

[Bimmeup02]

They are definitely 911 pistons as I have the other set as mentioned in the original post. I bought the engine that my pistons came out of and then did the disassembly as I just needed the engine for the Intermediate Shaft. Anyway, I knew things were a bit different when I looked at the pistons/biral cylinders and the heads and I have yet to find anybody that knows a history of this p/c & head combo on an early (1966) motor.

[Bimmeup02]

Oh Yeah, My Pistons, Cylinders and Heads are for sale along with the rest of my early 2.0 Litre stuff.

[BURN-BROS]

The early stock pistons did employ a ring below the pin. A piston that large would require a 2.2-2.7 head. I am guessing the compression would be around 9 to 1

[tom1394racing]

The early 2.0 pistons used in the 911's from '65-'68 look just like those pictured with the lower "slipper skirt" oil ring and deep valve pockets. These are 80mm diameter (not 87.5 mm).

87.5 mm cylinders would give 2.4 liters with a 66mm crank.

Hmmm....I am stumped on this one.

[Flat6pac]

Mahle of that size was for the 2.5 race engine but the race stuff had only 2 rings, compression and oil ring
generation was 72/73
Bruce

[Mark Henry]

I have a used set that looks just like that (do a search my name in the classifieds for pics) but they are mahle and were in 80mm birals....now I'll have to check the size to be sure.

[Bimmeup02]

Thanks for all your replies, but my pistons are in fact 87.5mm diameter as are those mentioned by hcarraro. I also have the heads that were on the motor when I took it apart, and there is a BIG difference between these P/C's, heads and my 2.0 litre stuff that I mentioned in my post that I have for sale. But thanks for telling me that 2.0 pistons are 80mm...Duh!

[304065]

Congratulations! You have a NOS set of CORVAIR pistons (3.44" bore)!

[Hcarraro]

John,

Thanks for your input. Care to share your source?

Henry

[Henry Schmidt]

I think they are EMPI big bore 911 piston. EMPI made them back in the 70s.
Almost possitive that they are not Corvair.

[tom1394racing]

A 22 mm wrist pin OD should confirm they are early 911 pistons

[304065]

Well they sure LOOK like 911 pistons-- the deep skirt with the tang that sticks down, the oil control ring below the pin. Even the oiling holes below the second ring are in the same place as my 80mm pistons.

But here's the rub. If they REALLY are 87.5mm, why? ST pistons were either 86.7 or 89mm. The 2,7 pistons were 90mm as of 1974. I'm not saying I know definitively that they aren't Porsche aftermarket but it does seem unlikely that somebody would tool up to produce a smaller version than what you could get from Mahle.

Nor do they meet the description of any of the Big Bore 1720cc 912 or Type 4 stuff-- a 1720 is an 86mm bore.

So I got to wondering, where would you find a set of six pistons that was 87.5mm, made in the early sixties with the oil control ring below the pin with the long tang? Also, the "STD" stamp suggests that they are domestic production- that's English, not German. No markings of any kind? 87.5mm is the exact size of one of the early Corvair pistons.

That said, a search of the Internet (great thing) suggests that Mahle made a set of 87.5 for "spec racing". . . that is certainly identical to the Mahle design. But they are not "long tang" . . . http://www.pbase.com/9146gt/my_9146_gt_project_my_engines_engine25ltr_mahle_87 5mm_pc

The mystery continues

[Hcarraro]

John C. Thank for your inputs. Actually if you Google 87.5mm porsche pistons or any number of similar machinations, there are many 87.5mm pistons and cylinders out there. And Porsche did in fact use 87.5mm pistons in several of their engines but the high dome is what eliminates the 356 or 912s from consideration.

Here is a fact. Porsche did build 30 special S/T rally motors (Type 911/20) using a 2.0 liter and or a2.2 liter magnesium crankcase as a base that was then bored to 87.5mm. With a 70.4mm crank and the 87.5mm pistons you get 2381CC. John Starkey's book mentions these special engines on page 15 and I found blurbs elsewhere on the Internet.

Tom, I am almost positive the wrist pins on these pistons is 22mm but haven't had a chance to get to my shop to measure them. I was hoping Patrick would chime in. He is the fellow that removed an identical set of these pistons and cylinders from a 66 911 engine bored to 87.5mm.

My gut tells me that these are not Porsche S/T racing pistons but perhaps a knock off. According to Starkey's book Porsche built these race engines for the 1971 race season, and at 250hp a 2.381cc engine in a light weight 911 had to be a real potent race car.

It doesn't surprise me at all that an aftermarket supplier like EMPI or other would reverse engineer an original Mahle piston and Biral Cylinder in order to build a knock off of high compression piston and cylinder, especially when you consider the horsepower potential of a mixed and matched use of Porsche engine components.

Yep, the mystery continues. Thanks to all for the inputs.


Henry

[Henry Schmidt]

I checked with a friend from the past that owned and raced a vintage 911 built by Wolfgan Mikie (sp) that used a set of these (cheater pistons). During his search to replace them he identified them and subsequently replaced them with the proper size Mahles.
They are in fact EMPI pistons. I would like to see the cylinders.
EMPI actually made pistons and cylinders, biral in fact around the same time they made the big bore biral barrels for 914 / VW type IV engines.

They do look allot like early two liter pistons.

[tom1394racing]

Henry S........I assume your picture is the Mahle 2 liter piston. I see what appears to be the Mahle casting marking on the dome.

Henry C....The 87.5 mm Mahle race pistons were forged pistons. The skirts on the forged pistons look like the ones pictured in John's link.

[Henry Schmidt]

Tom, you are correct. I posted the pictures to lay to rest the thought that pictures posted by hcarraro were anything but 911 pistons.
Tom I sent you a PM. contact me if you have any interest.

[tom1394racing]

Independent confirmation from our friends on EarlyS that these are Empi pistons.

Please help ID these pistons - Early 911S Registry Bulletin Board

[Hcarraro]

Well it is interesting that the fellow that sold me the EMPI 87.5mm pistons found the six corresponding NOS cylinders. He sent them to me earlier in the week. I haven't had a chance to photograph them but will post the images soon.

Too bad I didn't have the cylinders to sell with the pistons. Oh well such is life.

Henry