Boring 95mm cylinders

[lindy 911]

I am contemplating having my 95 mm cylinders bored and re-plated by a company in Wisconsin who specializes in nickel-silicone-carbide plating. Does anyone have any experience with this procedure? Does the 95 mm jug have enough meat to allow the bore to 98mm? What about the head gasket grove? Will it be compromised?

I know new 98's would be the hot set-up but the $ is way out there. I'm building a 3.2 SS with JE 10.5 : 1 pistons and twin plugs, 46 Webers or PMOs, and SSI. What is the largest diameter cylinder that will fit the SC case? I'm not against boring the case to fit larger cylinders. What about the heads on larger cylinders; can the SC head be machined to fit a larger diameter bore?

Thanks!

Lindy

[Steve@Rennsport]

Lindy,

95mm cylinders can be bored to 98mm, but that leaves little material to support the CE ring groove and thats an issue with a high-compression engine. Its not something I would do.

Your case can be safely bored to accept 100mm cylinders. There are several options here including Mahle's and Nickie's.

Your heads will need to be modified for any of these large-bore options, but thats not a problem at all,..... We do these all the time.

[Number1_dog]

I believe that Carrera 95mm Cylinders (without the ring grove at the top) can be bored to 98mm and used in a 911SC short stroke 3.2 but not the 911 SC 95 mm cylinders (with the ring grove on the top.) I found 98mm Max Moritz P&C here for my short stroke conversion on my 1979 911SC. Otherwise I was going to have EBS do the re-boring and coating as well as JE piston selection to match the re-build on a set of 3.2 Carrera Cylinders.

[Flat6pac]

When you use the Carrera cylinders, remember your torque to the heads changes to the Carrera spec 2 step torque.
Bruce

[VFR750]

Can someone explain why new 98mm cylinders work on a SC without modifying the head, but the 95 to 98mm conversions does not? I specifically want to know what people mean by "not enough material"

What is it about the existing sealing ring groove on a 95mm SC cylinder that is different than a new 98mm SC cylinder? Is the casting not thick enough for a new machined groove when you convert the 95mm SC cylinder to 98mm? Do you have to use larger diameter sealing rings for the 98mm cylinders?

Per Bruce Anderson's book, you don't have to machine the heads to take a Max Moritz 98mm cylinder. That is what is making me confused about the 95mm SC cylinder conversion. What is really going on?

Clarification of the details are appreciated (My SC has Alusil cylinders, don't you know....)

[EBS_Don]

The SC cylinders have groove at the top for a head gasket which is a little too close to the inside bore when modified from 95 to 98mm. The 3.2 cylinders have no groove in the top and therefore plenty to material. The thin ring of material left after boring out a SC cylinder will likely break upon use. A support ring can be made to fit in the groove but I'm not sure how well that has worked out for some that have gone that route. A bored and plated 3.2 cylinder is, essentially, a replica of a Mahle Motorsport 98mm cylinder.

[VFR750]

Don,

Does that mean the 98mm cylinder don't use a gasket between the cylinder and the head?

If so, I understand.

[Eagledriver]

Yes, no gasket.

-Andy

[VFR750]

OK, NOW I understand!

Bummer on the ring groove...... Too bad someone hasn't figure out how to cheaply weld in a solid ring to fill the space. A lot of good Alusil cylinders are going to waste.

[lindy 911]

By looking at the cylinders, I see no reason the head CE groove could not be welded up and then machined as though it never existed. The cost would be minimal compared to new 98 mm jugs. If there is no ring or gasket on the 3.2 jug, how does it seal? Will the SC head seal without the seal ring?

Lindy

[cgarr]

Originally Posted by lindy 911

If there is no ring or gasket on the 3.2 jug, how does it seal? Lindy

The 3.2 cylinders have a slight taper across the tops.

[Tom Sch]

hello,

is there any photo available where i can see the small material for the CE ring after the conversion to 98mm?
my motor builder here in germany always use the 95mm cylinders for the 3.2SS conversion...
most of the time with special manufactured JE pistons with 11.5:1 CR... ...no problems till now...

thanks

[Tom Sch]

hello,

to answer my question by my self... ...here you can see a 95mm cylinder modified to 98mm:



the motor is not finished at the moment, we will see



thanks

[78SCRSMAN]

^^^^^^^

VERY nice!

[Flat6pac]

The alucil cylinders can be used to open to 98mm because the bore will be replated in nikisil
Bruce

[tom1394racing]

The 3.2 Alusils or Nikasils can be opened up to 98 mm because there is no ring groove.

As best I know, you cannot safely open up the 3.0 Cylinders to 98 mm because of the issue pointed out by Steve Weiner and Don Weaver in the above posting.

If anyone is doing the 98 mm bore on 3.0 cylinders, I'd love to know how it is done and how it works out.

[safe]

Did they use alusil on the 3.2?

[tom1394racing]

Just like the 2.7 and the 3.0, the 3.2 P&C's were produced in both Alusil and Nikasil.

[pw36889]

Nice work, can someone tell me where we can find the cover used for this project. Which material is made?

thanks

[Tom Sch]

Originally Posted by pw36889

...can someone tell me where we can find the cover used for this project. Which material is made?...

hello,

the cover is from my motorbuilder, he will sell the parts also individual.
you can also buy these cover-parts here, he has also a nice smuggler box lid

All the parts are made of GFK.

thanks