MN12 T-Bird Master Cyclinder (MC) Swap

[DPDISXR4Ti]

I don't find a thread on this topic with install pics, so here's a couple....









MC as removed from junkyard donor MN12....

[DPDISXR4Ti]

Here's the link to Ed Key's site with more details...

http://www.key-ideas.com/DG_MasterCylinder.htm

Just in case it goes away some day, I'll cut & paste some of the written details below...

David has developed a master cylinder upgrade for the Merkur XR4Ti that utilizes a lighter and less expensive unit from a 94 T-Bird. Regarding the master cylinder, David writes:

"I wanted to find one with a bigger diameter piston bore if possible as well as a lighter one since the XR cylinder is cast iron. Never liked the XR cylinder as it is heavy and expensive. Ended up using a cylinder from a 94 T-bird, non-ABS with a 4.6. The T-Bird cylinder has a 1.062 in bore vs. the XR's 1.00 in. "

"The brake lines need to be changed as the XR had two ports for the front line where the t-bird only has one. This worked out in my favor as I want to install a line lock (for drag race burnouts) and I need one line common to both front wheels to do this. The rear line was going to be changed anyway since the stock proportioning valve was going to be removed."

I believe I used a 2-1 splitter block with 3/8-24" SAE fittings. An alternate possibility, if fitting a proportioning valve, might be using the block from the '87 - '93 Mustang which I presume uses metric fittings. A simple T fitting can be salvaged off a E30 BMW ('82 - '92 3-series), located just above the rear differential.

BMWe30-BrakeLineFitting.jpg (183.54 KiB) Viewed 2767 times

[John Brennan]

Thanks, Brad. I have a conversion kit (adapter and "slug") awaiting a set of PBR/ Scorpio brakes, and this is quite helpful.

[thesameguy]

I probably have some pictures from my install back in... '08? Amazingly the junkyard master cylinder I picked up then is *still* in the car. I've had zero issues with this setup, very happy I did it.

Edit: Here's the actual thread!

viewtopic.php?f=30&t=6313&hilit=master

That web host is long gone, but here are the images:







That was 11 years ago - the XR was still an automatic!

I've been through a complete set of calipers, but the used MC & Mike's braided brake lines are still doing a great job.

[my8950]

Interesting..
Everything for this is off the shelf?

[timxr8]

Interesting..
Everything for this is off the shelf?

To an extent. Do you have a tubing bender, extra fittings, and a flaring tool (both bubble and double 45 degree)?

[my8950]

Yes all that stuff I have, or can get. The MC is a direct fit though? No kits or special mounts made by someone 3 times every 5 years or something like that?

[In XS 7]

No, you will need the DG adapter kit and as you said, he don't make the adapter kit any more or he only make them from time to time.

[timxr8]

David Godfrey hasnt made that kit in a while. The kit was the adapter spacer and then a machined slug to take up the space for the shaft in the booster to Master Cylinder. Includes the mounting hardware and some fittings.

There's always the Scorpio ABS Master Cylinder route. Requires 2 extra holes and a notch in the firewall to mount it. Add in 2 wires to the pressure switch to activate a relay to power the pump. Pictures below show the physical install. The connection to the pedal is just like the XR. I have 2 extras. I'm using full ABS (switched to Scorpio spindles and bearing carriers with Cosworth 108mm stubs), so my wiring is simply the ABS wiring. I'll try and get some pictures of Jeff Esteban;s I helped with. Great upgrade and doesn't require vacuum.

[my8950]

Thanks Tim

[DPDISXR4Ti]

There's always the Scorpio ABS Master Cylinder route. Requires 2 extra holes and a notch in the firewall to mount it.

And here's a thread with more details on this swap...

http://forum.merkurclub.com/forum/viewt ... r+cylinder

[merkurdriver]

* Scorpio Master Cylinder the same as Sierra Cosworth Master Cylinder FYI.



All thats needed is that little notch in the firewall as shown in Tim's photo and it bolts in.

[timxr8]

As was stated in a related post: using this master cylinder (1.0625"/1 1/16" piston) is ~14% larger area than the Scorpio/later XR master (1" bore) and ~28% larger than the early XR master (15/16"/23mm).

Bore is the same as on the Mustang (pretty much every one since '94), so the PBR sizing will work and the rear caliper is a 38mm for the '94-'13 and 43mm for the '14+, so you can go either way with the rear brakes (Scorpio calipers or '12+ Focus).

[DPDISXR4Ti]

Of course I can't find my spare MN-12 MC when I need it. I know the rear fitting is 8mm, same as stock. But is the front fitting also 8mm, or is it 10mm?

Just trying to plan out how I'm going to plumb in my adjustable proportioning valve at the same time as the MN-12 MC swap.

[jkxr4ti]

Will wood has a valve with the metric fittings on it that are the same as the stock metric ones.
I was looking at this as an add on for mine when I put on the mark viii master.
http://www.wilwood.com/MasterCylinders/ ... =260-12627