Master cylinder swap - GB

[75glnt]

Hey guys. I'm in need of a new bmc (brake master cylinder). Before I buy a new 11/16 oem replacement.. Should I be looking for something else? Sigma, l200, etc?

I'll be running gh struts and brakes, so it's disc front, drum rear.

I'm not after a boosted setup unless its an easy swap, just trying to get it all working again

[davetrees]

Highly unlikely you will find an OEM replacement (11/16" Nabco) in Australia ..... they have been NLA for years. I found one on eBay ex the USA.

As a general rule, you should probably run the master cylinder that matches the brakes. I have no idea what size pistons the GH runs .... but probably more likely to be similar to GC/GD fronts than GA/GB? The MC for those is readily available.

[75glnt]

I have seen the gc/d ones on eBay... And can also get the 11/16 ga/b ones from a local parts store for $140ish.. Just wondering what's best... So a gh master. Do they NEED a booster?

[GB_BB4C]

I ran a GH master in my GB with no booster and 4 wheel disc's. just had to make up an adaptor plate for it to bolt to. I ran the bolts through the firewall, and no I don't have any pictures of it.

[75glnt]

Any/much mods for the brake lines??

Also, can't I just drill holes in the firewall to match the sigma master?

[GB_BB4C]

different screw ends had to be put on the lines to match the master. I didn't want to break off the two studs to hold the original master on (in case I wanted to revert the car back to standard), so I opted for a 25mm (was as long as the studs poked out) chunk of alloy to make the spacer, from memory the hole in the firewall where the master pokes through into the cabin is too small for the sigma one so will need modifying (enlarged). I used the Galant studs as dowels for the spacer and ran the bolts all the way through the firewall to the sigma master. I put sikaflex between the spacer and the firewall to stop water getting trapped behind. a longer push rod may have been sourced too.. probably from a sigma.

[75glnt]

Hmmm... Seems like a bitch for a rookie fabricator like myself

[GLANT]

11/16 unboosted with gh discs and stock drums is perfect! Passed engineers brake test with 151kwatw vr4 motor conversion in vic Mic. Any bigger and pedal will become harder mate.

[75glnt]

Yea we've spoke about this Pete hence why I'm happy to buy the stock one... Just thought I'd see if I'm better off with something else?