cylinder identification

[kiwi 1]

Hi trying to ascertain if cylinders are nikasil or alusil in my 77 911s 2.7l.Have tried magnet test with no obvious attraction to cylinder which is stamped Mahle along with piston.The cylinder has following nbrs 9ozn2w7,147 Mahle g... plus usual grade markings,piston nbrs c021 90l61 with original style 3 piece oil cont rings.In need of one cylinder, new/2nd hnd to replace victim of pulled head stud thus want to be sure of type.The cylinders are originals 140000mls on ex calif car,first time apart!

[NevenM]

Hi

The Nikasil coating is slightly magnetic (only on the inside of the cylinder) Its pretty obvious if you hold a magnet to a lump of ali there is nothing, nikasil a slight pull

HTH

Neven

[Bob Goding]

Hi,fellow Jafa!---I happen to have a new set of Nikasil P/Cs here,and I just had a look at the markings.
Mahle----90ZN2 W5. so I think you have nikasil, the w5 looks like a size grading. I have a used set of Alusil, but not much use to you. You could e-mail me at bobgod@clear.net.nz if you care to chat.
Bob

[James Renfroe]

Hi,

I would bet that these are Mahle Alusil cylinders. The difference in appearance between the Alusil and Nikasil is significant. The Alusils bores are a light aluminum color, a bare silicon/aluminum bore. The Nikasils are darker (bronze colored), and very slick. If the inner bore has no magnetic attraction, they are Mahle LS type cylinders.

I have emailed the Mahle folks in Germany (as will as other 911 experts) who all but say there is no way to distinguish Alusil or Nikasil Mahle cylinders by the serial numbers stamped on the cylinder base.

It has also been my observation that Mahle CIS Alusil pistons have squared piston skirts, while the Nikasil CIS pistons have a slight “humped skirt”. Check your piston skirts, if they are square (and assuming they are appropriately matched p/c), I bet they are Alusil.

Hope this helps!

[Bob Goding]

James, heres a couple of pics of my Cyl/piston. I bought these as Nikasil,but I would like you to elaborate on the piston skirt detail that you mentioned
Many thanks, Bob

[kiwi 1]

Thanks all for illuminating info.
James as per your piston description my pistons do indeed have flat skirt unlike Bobs pictures.This no doubt confirms I have alusil units,time to weigh up repair options!.Bob will contact, as recognise you as fellow airnzer ,Raro days!.
Thanks again

[James Renfroe]

Bob, thanks for these great pics!!

[cnavarro]

Bob, those cylinders for which you posted pictures are most definately nikasil, if you had any doubt about their composition. I'll see if I can find one of my tester alusil cylinders to post a side by side comparison, since it's pretty easy to visually tell the difference if you have one of each side by side.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[laughac]

I'm told these will fit into my 2.7 block even though they came from 3.0.

Can anyone help confirm this?

Cylinders have "MAHLE G**" cast on one side & "95ZN1W4" on the otherside, 11 fins.

On the inside of the pistons, "Mahle" "93L7" "++" "CO11"

[Steve@Rennsport]

3.0 pistons & cylinders will not fit a 2.7 engine case.

[laughac]

Thanks for clearing that up.

Would've been a shame to buy the wrong cylinders.

Now I'm looking at JE 9.5:1 and will verify that my current cylinders are Nickies.

[Flat6pac]

93L7 is 3,0 @ 8.5 cr.
Bruce