Mahle C pistons.

356 Porsche-related discussions and questions.
Post Reply
Message
Author
User avatar
Jan Balder
356 Fan
Posts: 320
Joined: Tue Oct 21, 2008 4:21 pm
Location: Netherlands

Mahle C pistons.

#1 Post by Jan Balder »

Hi all,

I'm sure this has been covered before but I cannot find it.

Is it advisable to cut Mahle C piston domes to a 22º angle to accommodate 22º cylinder heads or should I leave them 30º and use a 1 mm. shim below the cylinders ?

This is a Normal 616/1 engine but with S-90 heads .

Thank you,

Jan.
Jan Balder

User avatar
Martin Benade
356 Fan
Posts: 12193
Joined: Wed Nov 23, 2011 10:52 am
Location: Cleveland, Ohio

Re: Mahle C pistons.

#2 Post by Martin Benade »

Machining the pistons would be the better way to go, but if you still have a N cam, those heads will not be an ideal match, especially if you use the Solex 40 p11 carbs. You should work towards a good combination of parts.
Cleveland Ohio
62 Cabriolet
56 VW
02 IS 300
04 Sienna

User avatar
Jan Balder
356 Fan
Posts: 320
Joined: Tue Oct 21, 2008 4:21 pm
Location: Netherlands

Re: Mahle C pistons.

#3 Post by Jan Balder »

Thank you Martin,

The engine is a bit of a mismatch.
It has a S-90 camshaft,Solexes, heads, flywheel and engine cover.
Suppose the original case and crank were damaged in the past.

Jan.
Jan Balder

User avatar
Steve Hatfield
356 Fan
Posts: 1035
Joined: Wed Mar 26, 2008 8:54 am

Re: Mahle C pistons.

#4 Post by Steve Hatfield »

Jan,
If you are sure your engine has a S-90 flywheel, it must also have a S-90 crankshaft. And if that is the case, (speaking of cases) then you must also have S-90 cases owing to 55mm main vice 50mm. What makes you sure your flywheel is S-90?
Steve Hatfield
Fort Walton Beach, FL
'63 S90 Sunroof Coupe
'06 997S Coupe

User avatar
Martin Benade
356 Fan
Posts: 12193
Joined: Wed Nov 23, 2011 10:52 am
Location: Cleveland, Ohio

Re: Mahle C pistons.

#5 Post by Martin Benade »

Other than the notch for the bearing tang, the cases interchange for either size of bearing and the notch can easily be added. Also I have not seen why the S90 flywheel will not fit other cranks, seems like it might although it is said not to fit.
Cleveland Ohio
62 Cabriolet
56 VW
02 IS 300
04 Sienna

User avatar
Steve Hatfield
356 Fan
Posts: 1035
Joined: Wed Mar 26, 2008 8:54 am

Re: Mahle C pistons.

#6 Post by Steve Hatfield »

Martin Benade wrote:Other than the notch for the bearing tang, the cases interchange for either size of bearing and the notch can easily be added. Also I have not seen why the S90 flywheel will not fit other cranks, seems like it might although it is said not to fit.
Martin,
The S-90 f/w inner flange is not as proud and therefore takes a thicker spacer and one which needs to be a larger dia. to accomodate the 55mm no.1 bearing face. As to cases, I don't agree with your statement re interchange. Please elaborate.
Steve Hatfield
Fort Walton Beach, FL
'63 S90 Sunroof Coupe
'06 997S Coupe

User avatar
Martin Benade
356 Fan
Posts: 12193
Joined: Wed Nov 23, 2011 10:52 am
Location: Cleveland, Ohio

Re: Mahle C pistons.

#7 Post by Martin Benade »

The case bore diameter is unchanged, the larger journal uses a thinner bearing in order to fit the same bore.
Cleveland Ohio
62 Cabriolet
56 VW
02 IS 300
04 Sienna

User avatar
Steve Hatfield
356 Fan
Posts: 1035
Joined: Wed Mar 26, 2008 8:54 am

Re: Mahle C pistons.

#8 Post by Steve Hatfield »

In the immortal words of Johnny Carson, "I did not know that."
Thanks Martin
Steve Hatfield
Fort Walton Beach, FL
'63 S90 Sunroof Coupe
'06 997S Coupe

Dick Weiss
356 Fan
Posts: 4183
Joined: Sun Apr 20, 2008 12:54 am

Re: Mahle C pistons.

#9 Post by Dick Weiss »

You don't need to cut the C piston tops for the 22 degree chambers--there's not much to cut. Using the 1mm spacer (or multiple shims) to suit the exhaust valve clearance
will be OK. Just make sure the cyl's are @ even heights and the head seats are w/in .0005" for sealing the chambers.

Dick

Post Reply