Mahle 2.7 High Compression Pistons

jbell959 · 01-28-2005, 03:46 PM

I was looking at an engine that the owner claims was rebuilt 9 years ago with high compression Mahle 2.7 pistons. He showed me a copy of the work order and the part number for the piston and cylinder set is 911103949HP. It appears to be the same number as the CIS pistons with the HP at the end. Is anyone familiar with a high compression set made by Mahle with that part number?

Yellowbird RS · 01-28-2005, 05:56 PM

2.7 lts. Mahel CSI compression 8.5:1 part# 911-103-949-01

Early_S_Man · 07:05 PM

Since that number appears to be for normal CIS pistons ... either the owner is misinformed or trying to misrepresent what is in the engine! Some people call the 175 hp 1974 911S CIS pistons 'high compression' ... when compared to the base 911 engine pistons for the 150 hp model!

Ask the owner for the compression numbers, and to do the test in front of your eyes ... an 8.5:1 engine will produce 170 - 190 psi, whereas high compression pistons should produce 200+ psi test numbers!

jbell959 · 01-28-2005, 07:11 PM

Thanks for the information... This is helpful.

wowzer911 · 01-28-2005, 07:21 PM

2.7L IS EITHER 8:1 OR 8.5:1 SO HE'S BEING UP FRONT WITH YOU. AFTER NINE YEARS AND A COLD ENGINE(IF ENGINE IS OUT OF THE CAR) DON'T EXPECT THOSE KIND OF NUMBERS

klaucke · 01-28-2005, 07:23 PM

Warren, I have a 74 911S and it only produces 155ish specs at cranking for compression, although I suppose my battery could spin the engine faster for higher numbers. I bought some used pistons at one time though, and I recieved two types due to shipping complications. One set looked like the above shown set, my set, IIRC doesn't have quite the same size hump (although the wrist pin must be higher, relatively, to yeild higher compression). Both types of pistons were from CIS 2.7's, so more than one compression ratio or type must have been used in 2.7's. Then again, I have a California model so maybe my 911S has low compression pistons (voiding my wrist pin idea)???

jbell959 · 01-28-2005, 07:27 PM

The engine is in the car. He claims they are 9.5:1 or greater. I read through some posts and there was mention of a high compression euro piston that Andial was selling. I thought it may have been those.

wowzer911 · 01-28-2005, 07:32 PM

I DON'T BELIEVE MAHLE EVER MADE 9.5:1 2.7L PISTONS

Yellowbird RS · 01-28-2005, 07:44 PM

Those are for the 911 U.S. specs. the euro part #911-103-928-01 compression 8.5:1

The 9.3:1 are for 1980-83 3.0 lts. part#930-103-977-03

Yellowbird RS · 01-28-2005, 07:49 PM

jbell959 · 01-28-2005, 08:05 PM

Here are a couple of the posts that mention higher compression 2.7 pistions.

2.7 RS engine CR increase?

2.7 Mahle P&C's

Yellowbird RS · 01-28-2005, 08:16 PM

I'm running mahel 2.9 lts. high compression (10.5:1) on my '74 Carrera and yes they make HC pistons & cyls. but jus to upgrade the 2.7 lts. to 2.8 (RS 9.5:1 ,RSR 10.5:1) and 2.9 lts.

Carrera3.5L · Carrera3.5L's Garage

Mahle makes a 90mm piston and cylinder that is rated at 10.3:1. This is for 2.4L and 2.7L engines with MFI or carbs. For an RS, it raises the compression from 8.5:1 to 9.5:1

Bore: 90.0mm
Cyl height: 85.6mm
Piston Pin: 22x58mm
Comp Ring 1: 90x1.5
Comp Ring 2: 90x1.5
Oil Ring: 90x4.0
Head Gasket: CE-Ring

I could give you the Mahle internal piston and cylinder part numbers, but then I would have to kill you.

Ralph

wowzer911 · 01-28-2005, 10:26 PM

NOW I'M CONFUSED

Early_S_Man · 01-28-2005, 10:27 PM

The current Mahle high-compression piston sets are a recent development -- less than five years old ... so, that would preclude their use in a rebuild nine years ago! Besides, they don't have Porsche part numbers!

Carrera3.5L · Carrera3.5L's Garage

Quote:

Originally posted by Early_S_Man
The current Mahle high-compression piston sets are a recent development -- less than five years old ... so, that would preclude their use in a rebuild nine years ago! Besides, they don't have Porsche part numbers!

Sorry, but you are wrong. I sold these pistons and cylinder sets 15 years ago while at Andial, which is why I have the internal Mahle piston and cylinder part numbers. These part numbers wouldn't mean anything to the guys at Mahle Motorsport in NC, but the folks at Mahle in Germany would know exactly what they were.

You are right with the statement that the sets don't carry a Porsche part number, never said they did. Don't know if these sets are still available or not, but they did exist for quite a long time.

Ralph

Carrera3.5L · Carrera3.5L's Garage

Here is the info that I have for 90mm pistons & cylinders. Note that this is from my notes that are from the late '80's so don't consider it up to date:

Stock Pistons & Cylinders
911 103 928 01...90mm w/ 8.5:1 CR...Nikasil Cylinder
911 103 949 00...90mm w/ 8.5:1 CR...Silumal Cylinder
911 103 949 01...90mm w/ 8.5:1 CR...Nikasil Cylinder
911 103 951 01...90mm w/ 8.0:1 CR...Nikasil Cylinder

"Racing" Pistons & Cylinders
90mm w/ 10.3:1 CR*...Nikasil Cylinder
*CR may vary depending on components used

BTW, I have no idea what Silumal cylinders are...

Hope this info helps some of the confusion and doesn't create more!

Ralph