Correct Power Booster Application

[Ole]

Rather than steal somebody else's thunder I thought I would seek some advice along similar lines to Nes232's query re the correct power booster to use. I am hoping that Ken may be able to provide some sage advice.
I have fitted HZ Girlock calipers and discs to our FC wagon project that will be running a VE Commodore V6.
What is the best firewall mounted booster and master cylinder combo to use. I have access to an XB Ford booster, a Gemini booster or the booster from the VE donor car. If none of these are suitable I am willing to use whatever is best based on the advice I get.
Regards Ole.

[NES304]

Would have been happy for you to join in.... I posted pics of mine installed

[Ole]

Thanks for that NES232, I wasn't sure about the protocol of joining in with my own enquiry. I've checked out your photos and the others in Show us your boosters. Like you, I'm looking forward to some expert advice before I start cutting too many holes in the firewall.

[mcl1959]

There are only a few rules to remember when choosing booster/master cylinder setups

1) most early single piston calipers require a 1 inch (25mm) bore master cylinder - The HR, Torana, HKTG, HQJXZ and early Commodore are all like this. Most early Holden and Ford twin circuit masters are 25 mm bore. Very few Jap are 25 mm.
2) Most boosters are OK to use but its clearly wisest to use one which will bolt up to the master cylinder - Gemini booster / XB master has been a classic choice for years but not all Gemini boosters suit and there are a few tiny mods which need to be done to make it work properly.
3) Later Commodores like VS had a smaller diameter bore master cylinder but it is obvioulsly well suited to VS brakes.
4) The VT and later have twin piston brakes and a retraction system to draw the pads away from the rotors - The master cylinder has a "fast fill" or dual bore feature specifically designed for the calipers.
Unfortunately the later boosters don't adapt well to the earlier master cylinders.
The Cal custom twin diaphragm booster adapts well to the XB master cylinder and is very good if you want to run manual gearbox and have big front brakes.
5) Why is XB master cylinder preferred - easy - the pipes exit on the mudguard side rather than the engine side. In an early Holden the V8 exhausts run close to the master cylinder and you really don't want your master cylinder pipe work running close to your exhaust.

To sum up - most boosters can be used but there is no point using a booster which won't work with any of the master cylinders you can use. It is imperative to match your master with your front brakes - a proportioning valve can sort out the rear bias fairly easily but don't over brake the rear with Commodore discs if you are only running HQ fronts for example.
Ken

[NES304]

Ahh Ken, you are a wealth of knowledge. The master cylinders I have from both vehicles are (to what I can tell) identical and bolt straight up. I am running VS commodore both front and back.

Just read through this,,,,, interesting read, still cautious though.
The early commodore guys going nuts for the VT booster and master
http://www.calaisturbo.com.au/showthread.php?t=134762

[Ole]

Thanks Ken, that is exactly the type of in-depth advice I was hoping for. I very much appreciate the effort that you have put in with your response. I made some independent inquiries yesterday with a local brake specialist, while waiting for forum advice, and he pretty much echoes your advice, word for word. He didn't mention the Cal-custom option so that is a bonus. I will be running an auto transmission so I will go with the XB booster and master cylinder option. Thanks again for your advice, it is the expert advice that I expected after reading many of your previous postings.
Regards, Ole.

[NES304]

Dammit I accidently hijacked your thread. Sorry

[mcl1959]

Nes -I have read the commodore article; the guys are using the VT master when they have fitted VT brakes to early Commodores - this makes absolute sense and agrees with what I have said

Ken

[NES304]

Thanks Ken,
I picked up a set of VS pedals and Booster (already had the master) for next to nothing.

Pity, the VT booster just looks heaps neater