Early aluminum cases

John Druckrey · 05-26-2006, 07:12 AM

What is the largest size cylinder that can be installed in an early "0R" aluminum case? Realizing of course that the case would need to be bored to accept larger cylinders. I have a NOS set of RS cylinders and pistons that I would like to use. Thanks

andrew15 · 05-26-2006, 07:26 AM

Yes, the early aluminum case can be bored out to accept 90 or 92 mm P&C'sb (both have the same outer diamater on the cylinders). I don't think 95mm can fit without major reworking - due to head stud spacing changes.

Regards,
Andrew M

kenikh · 05-26-2006, 04:06 PM

The nice thing about Aluminum is that you could rework the stud spacing with some expert welding. Don't think I haven't considered making a short stroke 2.8 on a reworked early aluminum case...

blue72s · 07-16-2006, 06:27 PM

Quote:

Originally posted by kenikh
The nice thing about Aluminum is that you could rework the stud spacing with some expert welding.

Wow, first I've heard.

With regard to 3.0 carrera/turbo case, is it possible reduce the stud spacing from 86 to 80mm? What's the standard spigot diameter of 3.0?

Wayne 962 · Wayne 962's Garage

Quote:

Originally posted by blue72s
Wow, first I've heard.

With regard to 3.0 carrera/turbo case, is it possible reduce the stud spacing from 86 to 80mm? What's the standard spigot diameter of 3.0?

There's really no point. For anything up to 2.9 or so, you can use the early 911 cases. For anything 3.0 and later, you can use the Euro Carrera cases...

-Wayne

Henry Schmidt · Henry Schmidt's Garage

If you are talking about 90 mm RS cylinders, yes the 2.0 aluminum case can be bore to fit them. Remember that the 90 RS pistons are very low compression 8.5 and when used on a short stroke crank offer even lower compression. Somewhere around 8.0:1
We resist this conversion because the spigot flange gets very thin.
What we do is bore the spigot hole to 95mm vs. 97 mm and turn the cylinders to the smaller size.
This gives you a better flange for the cylinder to sit on and the cylinder has little or no compromise.

As for changing stud spacing, we have done this on a number of cases for a number of reasons. The easiest way to change stud spacing is the off set bore for a CaseSaver. CaseSavers come in many different sizes making this a great method for stud relocation with no welding.

A prime example of this conversion was to put a genuine RSR 3.0 cylinder on a 2.7 case.
We also converted a RSR 3.0 case the fit stock 911SC cylinders and heads.
No issues with these conversions.

We have also converted 3.6 100mm cylinders to fit a 3.0-3.2 case. Instead of moving the studs, in this case we slotted the cylinders to fit the stud spacing and turned the spigots to fit a bored out case.

tadd · 07-21-2006, 04:36 AM

Henry:
Have you ever considered the SC head as a 2.8 RSR replacement by inside oversize - offset drilling of the stud holes? Then all that would be needed were some stepped washers to center the heads. The machine work would be cheap as it would just be a plunge cut for each hole and then a few centering washers whipped out on the lathe. Since the pluge cut would be square to the the fin it would be no where near as challanging as adding a second plug.

tadd

John Druckrey · 07-21-2006, 08:32 AM

Henry:

What would be the consequences/ramifications in using a 70.4mm stroke crankshaft with the RS pistons/cylinders and early case?

Henry Schmidt · Henry Schmidt's Garage

Very nice combination.

You will be forced to bore the case, but as I stated before bore the case to 95.5 and trim the cylinders to fit and you will have a ver nice engine.

John Druckrey · 07-21-2006, 10:09 AM

Henry:

Just did a test fit of a cylinder and it fit just fine on the original studs. I suppose that while the case is being bored I should do the other typical modifications such as piston squirters. Anything else that you would sugjest while the case is on the Bridgeport?

blue72s · 07-21-2006, 11:42 AM

Quote:

Originally posted by Henry Schmidt
If you are talking about 90 mm RS cylinders, yes the 2.0 aluminum case can be bore to fit them. Remember that the 90 RS pistons are very low compression 8.5 and when used on a short stroke crank offer even lower compression. Somewhere around 8.0:1
We resist this conversion because the spigot flange gets very thin.
What we do is bore the spigot hole to 95mm vs. 97 mm and turn the cylinders to the smaller size.
This gives you a better flange for the cylinder to sit on and the cylinder has little or no compromise.

As for changing stud spacing, we have done this on a number of cases for a number of reasons. The easiest way to change stud spacing is the off set bore for a CaseSaver. CaseSavers come in many different sizes making this a great method for stud relocation with no welding.

A prime example of this conversion was to put a genuine RSR 3.0 cylinder on a 2.7 case.
We also converted a RSR 3.0 case the fit stock 911SC cylinders and heads.
No issues with these conversions.

We have also converted 3.6 100mm cylinders to fit a 3.0-3.2 case. Instead of moving the studs, in this case we slotted the cylinders to fit the stud spacing and turned the spigots to fit a bored out case.

What suggestion do you have for 92's? (aluminum case)

Henry Schmidt · Henry Schmidt's Garage

The stud spacing was never in question. The stud spacing did not change until the 3.0 911 SC.

With the exception of RSR racing cases and the 76-773.0 Euro Carrera and the 3.0 Turbo.

I would do an oil bypass modification.

No boat Tailing.

One very nice up grade is to machine the case for late style counter shaft bearings.
Good luck

blue72s · 07-21-2006, 04:07 PM

Thanks Henry but I meant this:

Quote:

Originally posted by Henry Schmidt
We resist this conversion because the spigot flange gets very thin.
What we do is bore the spigot hole to 95mm vs. 97 mm and turn the cylinders to the smaller size.
This gives you a better flange for the cylinder to sit on

As you know, 92mm cylinders cannot be turned to the smaller size so what is the solution to the spigot flange problem?

Henry Schmidt · Henry Schmidt's Garage

You would not be able to trim the cylinders on a 92 mm cylinder as I suggested in the earleir post.
Trimming the cylinder only works with a 90mm cylinder.

When attempting to run 92 mm cylinders on an early aluminum case you will have to bore the case to full size 97mm. That leaves a very small sigot but , oh well.

blue72s · 07-21-2006, 04:42 PM

Would it be possible to enlarge the spigot flange by welding some aluminum around the outside of the spigot flange?

Henry Schmidt · Henry Schmidt's Garage

It might make more sense to machine 1/2 of the spigot flange off and machine a spacer to replace the flange.
If you were to machine a small step on the inside of the spacer to fit securely around the flange you would be able to press the new spacer on with a sealant (574 or perhaps an epoxy) and you would have the cylinder support you desire.
Final deck all the flanges to the height deemed appropriate by the deck height of the pistons.

The process would be simple but certainly time consuming.
Worth the effort? Perhaps