Dual circuit master cylinder

[funkyscooter]

Reading with interest as I need to come up with a solution too. Don't know if any of theses are any better - but they are cheaper! https://www.partsforhotrods.com.au/shop ... inder-kits

[FireKraka]

I used one of the 7" double diaphragm chrome ones from evilbay (just for the bling aspect ) but make sure you get the right size master cylinder for your application, I have 4 wheel discs, commodore all the way around and normally the commodore master cylinder is 15/16th (I think it is) the smallest Chrome master I could get was 1" that was the second one the first was an 1"1/8 and very hard pedal licensing would not pass me for rego so had to go to 1" it is ok but could be a bit softer pedal.
So the bore does make a big difference
Neil

[Cliff Regan]

I purchased mine from V6 Conversions, theirs is a 15/16 bore, also comes with a bracket to bolt onto the firewall. (4 wheel commodore disks)

[gpi]

a master is only as good as the slave it serves

[mph]

I picked up a offset bracket yesterday and gave it rough sit in , it still seems mighty close to the bonnet hinge when i center up the fb brake pedal rod to center of the hk rod arm part.

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[Devilrod]

MPH timely post. Here are a few things I’ve worked out this afternoon. Now I took the bonnet off for access then had to improvise to move the hinge up and down so ignore my makeshift leverage device.

If you align the original upper firewall master cylinder bolt hole with the same bolt hole in the bracket (top rhs hole) it clears the spring as it pushes the bracket further inboard and clears the spring.




Next up flip the adjuster rod bracket so the flat side is on the outer and the bent side is on the inside of the car.


This too helps align the rod better. I’ll need to enlarge the hole slightly but it seems to all line up and work. Down side is it will mess with a clutch master but I think some creative reworking of the bracket will fix that problem.

Next up I made a sub par 7” cardboard/paper template just as a roughie to see how close it would put the spring to a dual diaphragm 7” booster.



So now I need to decided. Make a better replica booster or bite the bullet and order one. Then continue mocking it all up. It’s going to be tight but may just work.

[Devilrod]

I’ll add that at the moment I have washers behind the bracket to pack it out for now. I think I’ll either flatten the firewall or botch the bracket to clear. Still undecided on that one.


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[ardiesse]

Posting before thinking here, but -

If you've installed the HK relay-arm-booster-mount, then you could try an HK-T-G clutch master cylinder. The mounting holes are already there in the bracket; and if the centreline of the KTG master cylinder is left of the original, you could put a spacer between the clutch pedal and the pedal box. The downside is that you'd need to get an extended pedal shaft machined up.

Rob

[Devilrod]

Posting before thinking here, but -

If you've installed the HK relay-arm-booster-mount, then you could try an HK-T-G clutch master cylinder. The mounting holes are already there in the bracket; and if the centreline of the KTG master cylinder is left of the original, you could put a spacer between the clutch pedal and the pedal box. The downside is that you'd need to get an extended pedal shaft machined up.

Rob

That could work too, but the easier way would be to mod the bracket it would take less work and keep your pedals spaced nicely. I’m lucky though mines an auto so it won’t be an issue


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[funkyscooter]

Crazy thought - if the space between the spring and the dual diaphragm is the issue, then could you use a skinnier spring?
More effort to lift the bonnet and finding a spring that is the right length are two obvious reasons against crazy thought.

[Blacky]

Crazy thought - if the space between the spring and the dual diaphragm is the issue, then could you use a skinnier spring?
More effort to lift the bonnet and finding a spring that is the right length are two obvious reasons against crazy thought.

One of my cars had no spring on the drivers side and a gas strut in the centre attached to the under bonnet bracing - worked a treat

[Devilrod]

One of my cars had no spring on the drivers side and a gas strut in the centre attached to the under bonnet bracing - worked a treat

I’ve also seen no springs and a chain cut to the right length that gets hooked on.

So many options….

[mph]

Just a thought if keeping the original hinges maybe approximately 200mm or 175mm gas strut work ,lop the spring and spring hooks off will gain around 40mm clearance then a gas strut will be about 12mm


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[BILLY BLACKARROW]

I think gas struts are a good idea use less room BUT i would talk to someone that fits them as it's not just fit and play there is a lot going on with the angle of the dangle.

[funkyscooter]

I think struts are a good option - Would be great if you could mount off the hinge, but will it work?. Your first image looks like the strut would need to be tiny when closed. The second looks like initially the top hinge at the mount point moves back and then swings through and pivots forward, so in the act of opening maybe it would assist then get heavy, then assist again.
If the bottom mount of option 2 was mid way down the gutter of the sub frame, I think that would work, but no doubt there are things to fowl on there too. And not as elegant.
Are there struts that pull instead of push? Then you could locate it where the sping is.
Or just ditch the spring and use a broomstick