Dual circuit master cylinder

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138
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Dual circuit master cylinder

Post by 138 »

Will any other Holden (or any brand for that matter) dual circuit master cylinder (for drums) bolt up to my existing firewall mount?
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Harv
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Re: Dual circuit master cylinder

Post by Harv »

Not sure if any are a direct bolt up, but the Gemini booster is pretty common. It is small enough in diameter to clear the bonnet hinges, which can foul with larger booster/master combinations. The earlier Gemini boosters are used, which have a horizontal bolt pattern (later Geminis used an angle mount). The booster is mated up to an XA/B/C &*#@ master cylinder, which is dual circuit (PBR part number P6258a). The master cylinder pushrod has to be extended slightly so that it protrudes 1.5mm from the booster face (in order to provide appropriate booster pre-load). The booster mounting bracket mounts neatly to the firewall, though some holes have to be enlarged/drilled.

There are some photos of the setup on my build thread from memory (http://www.fbekholden.com/forum/viewtop ... 3&start=60).

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Harv
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Errol62
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Re: Dual circuit master cylinder

Post by Errol62 »

CRS used to supply an adaptor to bolt up HQ drum brake dual circuit master cylinder to FE - HR. This gives you unboosted dual circuit brakes. Harvs solution will give you boosted dual circuit to suit disc or disc/drum with compatible slave and proportioning hardware. May also work with drum/drum combo.


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Harv
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Re: Dual circuit master cylinder

Post by Harv »

Errol62 wrote:CRS used to supply an adaptor to bolt up HQ drum brake dual circuit master cylinder to FE - HR.
Interesting... hadn't seen that one before. CRS now advertise an adaptor for HQ master to EJ/EH: http://www.rodshop.com.au/holden/fb-ek/ ... aptor.html. They list it on the FE/FC, FB/EK and EJ/EH pages... wonder if it fits FB/EKs too?

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Errol62
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Re: Dual circuit master cylinder

Post by Errol62 »

Same master from factory so should do. I'm planning to fit one and boost the front circuit only then run standard EJ rear hardware and HR discs front. The booster will be hidden under the rear cargo (van) with the battery. One day!


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gpi
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Re: Dual circuit master cylinder

Post by gpi »

Harv wrote: Mon Dec 19, 2016 3:50 pm
Errol62 wrote:CRS used to supply an adaptor to bolt up HQ drum brake dual circuit master cylinder to FE - HR.
Interesting... hadn't seen that one before. CRS now advertise an adaptor for HQ master to EJ/EH: http://www.rodshop.com.au/holden/fb-ek/ ... aptor.html. They list it on the FE/FC, FB/EK and EJ/EH pages... wonder if it fits FB/EKs too?

Cheers,
Harv
doesnt fit fb ek due to the bumps in the firewall. i milled it down to fit.
might cast a few considering its nothing like how i originally bought it.
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Errol62
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Re: Dual circuit master cylinder

Post by Errol62 »

How about some photos? I'll probably be keen to get one if you go ahead.
Cheers
Clay


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Re: Dual circuit master cylinder

Post by Trev »

I bolted a HG dual circuit directly to my firewall, had to enlarge the hole and flatten the pressings but it went on no problem.
Then used a remote booster.


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Errol62
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Re: Dual circuit master cylinder

Post by Errol62 »

Boosting front circuit only I assume Trev. Drum front compatible cylinders on rear?


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Re: Dual circuit master cylinder

Post by Trev »

I had a HR disc front end sorry Errol I should have said.
Yes front boosted only.


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Re: Dual circuit master cylinder

Post by Errol62 »

That is what I plan doing. Worked okay Trev?


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Re: Dual circuit master cylinder

Post by Trev »

I used that for about 10 years then started having trouble with front brakes locking up so I went to a fully boosted system.
Ended up being as simple as a blocked flexible hose in the rear end. So didn't need to change after all.


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Re: Dual circuit master cylinder

Post by Errol62 »

Cheers Trev
Good to know.


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Re: Dual circuit master cylinder

Post by Mick »

I've used the method trev described a few times except i leave drum brake compatible set up on rear, the last time it had to be brake checked for engineering the guy said they were fantastic and wanted to know what the set up was so he could use it if need be
sometimes yor just better off shitting in yor hands and clapping

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Errol62
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Re: Dual circuit master cylinder

Post by Errol62 »

Cheers Mick
Good way to keep the engine bay uncluttered if you can hide the remote booster some where. I'm thinking to put booster behind the seat in the van together with the battery. Means some extra plumbing but reduces understeer and keeps engine bay tidy.
Anyway sorry to hijack your topic 138.
Cheers
Clay


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