Mahle Nikasil cylinder wall thicknesses

[blue72s]

What is the cyl wall thickness of the following respectively:?

90mm

92mm

93mm


Thanks.

[Bobboloo]

It varies depending on where you measure the cylinder but if you figure that the spigots are 97mm on a stock 2.7 then the math suggests that the cylinder wall is as follows at the base of the cylinder.

90mm = 3.5mm

92mm = 2.5mm

93mm = 2.0mm

There in lies the problem with the 2.9L conversion kit. 2mm of cast aluminum = not enough.

2mm of billet aluminum as in Nickies might work however.

Keep in mind that the cylinder is thicker at the top where compression is highest. You'll notice that the fins are wider at the top which also increases strength.

[blue72s]

Thanks Bobby.

2mm of cast aluminum = not enough.

Is 2.5mm still not enough?

[Bobboloo]

Evidently.

Steve Weiner says that the 2.8 conversions he's done have held up just fine over the years and I respect his experience in this matter. He recommends against the 2.9 conversion, however, for reasons of the cylinder thickness.

His input played a major role in my decission to build a 2.8 for my 71'S.

Grady also built the 2.8 for Gregs' aka (911RST) 72' T 30 years ago and it's still going strong.

[jpnovak]

And Greg's car is really strong. I have been in the passenger seat and was grinning like a little kid!

I wonder if you could bore and plate the Alusil 2.7 cylinders to accept the 2.8 pistons in JE brand. It would be similar to the 3.2 conversion process. There are a lot of dead 2.7 jugs laying around for nothing.

[Scott Clarke]

Jamie-
Yes, you can. EBS does this a lot. It costs about $100 more than just having 90mm cylinders reconditioned.
-Scott

[Bobboloo]

I think it runs something a little north of $1200 to get a set of 90mm's bored and plated. Another $1000 for the JE's so it's a little cheaper than buying new RSR P+C's but keep in mind they are still used cylinders even though they've been reconditioned. So a low mileage set is the best starting point because they haven't been heat cycled as much.

[Scott Clarke]

In addition, new Mahle 92mm cylinders have no head gasket groove, eliminating the failures that have occured with these cylinders in the past. I bet that you'd be hard pressed to find a set of Mahles for less than 3K.

[Bobboloo]

Scott, That makes sense since that part is so thin and the highest compression area. I suppose you could have the CE groove welded up before they cut the cylinders but at that point it might be cheaper to just buy new.

If enough people are interested I'm sure Wayne could make a group buy of the new RSR 2.8 P+C's. I got a set of Charles' "Nickies" so I'm set already.

[Steve@Rennsport]

Bobby:

The Mahle 92mm RSR P/C's are now out of production as of mid 2004 and there will be no more, according to folks I spoke with at Mahle in Germany last year.

There are a few vendors that have 2-3 sets and thats it. These are THE best quality P/C's you can buy, albeit not cheaply.

[Bobboloo]

Didn't know that. If that's the case, Blue 72, I saw that CDOC had a couple of sets left for around $2800. You should probably jump on it. They advertise in Excellence.

[blue72s]

Bobby
You have a PM.