930 mc & repositioning bolt holes for rear calipers

[Scarface]

Guys,

Would the 930 master cylinder (23mm) fit into an 87 Carrera?
Also, does anyone have pictures of milling and repositioning bolt holes for 3.6 turbo rear calipers? (To fit stock 930 discs)

Fronts will be a Big Red kit.

I'll be doing a DIY so any help will be greatly appreciated.

Scarface.

[Bill Verburg]

Here's a pic from the rear of my car. As you can see the original holes need to be plugged and new ones drilled slightly closer together, the Carrera backing plates need to be discarded or replaced with 930 parts. By the way the 993tt rear calipers are not the most appropriate for use with "Big Red" front calipers due to mismatched piston sizes. The 993 tt used 44/36 mm pistons front and 4x28mm pistons on the rear, this was due to the increased rear weight bias of those cars. All of the 964/993/RS etc used the 44/36 fronts with 30/34 rears.

[911pcars]

Hey Bill,
Is it necessary to dissassemble the caliper to weld/plug and redrill the mounting holes?

Seems like it would be easier to machine despite the hassle of splitting the halves.

Sherwood Lee
http://members.rennlist.org/911pcars

[Bill Verburg]

Mine were apart for a rebuild anyway so i'm not sure if disassembly is required, my guess is that there is not enough heat to cause a problem. The concern of course is excessive heat on the seals.

[This message has been edited by Bill Verburg (edited 06-19-2001).]

[Scarface]

Bill,
is it as simple as just welding shut the hole first and drilling the other? (TIG welding?)

will the stock 930 mc bolt on? or would you recommend the mercedes mc?

thanks.

[Bill Verburg]

Machine a plug for the existing mounting hole, weld in place, redrill slightly closer together. you can just make out the outline of the original washer position in the pic at point 'A'. The rotor is stock 930(299x28 mm), sans backing plate.

The 23mm Mercedes mc is for non-boosted cars(pre 78) which had 19mm mc oem. The later boosted cars have a larger mc standard(20.4 mm in at least 84-89). The 963 C2 with vacuum boost used a 23.8 mm mc, the later cars used up to a 25.5 mm mc with hydraulic rather than vacuum boost. Again I have not looked into swapping boosted mc so i'm not much help there. But if it was me I would look into the 964 vacuum boosted mc for a possible transplant in you car.

The standard 930 mc is likely a bolt on, but is also probably too small for the later Brembo calipers with their larger piston sizes. The 78-89 930 calipers didn't have really large piston sizes and work ok with the smaller 19 mm mc.


[This message has been edited by Bill Verburg (edited 06-20-2001).]