32 replies to this topic

[TerrA LX]

Are proportioning valves interchangeable between the large holdens, tornans and geminis?

[toryman76]

when you throw them in the bin they are all the same....get your hands on a VN-VR booster and master and fit the whole lot....you need to "adjust" the pushrod and obviously the lines but it has the prop valve as part of the master....just remove the bracket from the booster and it bolts in...havent done it to mine yet but a mate put one in his and it was easy

and by "adjust" what do you mean? can this be done by yourself or do you need to get someone to do it for you?

[toryman76]

i believe you have to shorten the pushrod and maybe bush or drill the hole....its on my list of things to check out this weekend...i have the booster and a pulled apart UC to trial fit it onto...will let you know

edit...but these masters would suit rear discs...not sure if any good for drums

ok that would be good if you could check it out. thanks for the edit too becuase i have rear drums. looks like i might just have to stick with the standard gear... unless, would a standard master bolt up to one of these boosters?

[dattoman]

Props are different because of the crack pressure for rear discs
Commy booster neads rear rod modified to suit Torana
There are 2 different rod configs depending on the pedals
Torana master does not fit commy booster... no idea why you would want to anyway
Commy master does not fit Torana (cept late UC which had a commy master anyway)
Rear disc or rear drum commy uses the same master
Avail in 15/16 or 1" (1" is torry too)

[dattoman]

Who said anything about 1 1/4" ?


Is that the imaginary Commodore master I have heard of ?

1" guys... why downsize from original

[TerrA LX]

My question had nothing to do with rear disc brakes or commodores.

[toryman76]

My question had nothing to do with rear disc brakes or commodores.

Sorry ALX76... i think i started the tangent off from your question

[dattoman]

VS was 7/8 main bore with 1 1/8 fast fill primary bore

And has nothing to do with Toranas
They ran a plastic booster which is shit too.

Lets not confuse road cars with race cars that ran Internation truck master cylinders and 4 pot AP calipers all round

[Statler]

VN booster requires shortening of the rod. Yes!
About 4mm i think.

Smart, cheap modification. Those double diaphram? V8 boosters are getting difficult to find in good nick!

Note: brake lines need mods also if deleting the external proportioning valve.

[TerrA LX]

Maybe i should start my own thread?

[ls2lxhatch]

Dattoman. Props are different because of the crack pressure for rear discs

It would appear that the answer is no because each prop valve is setup for a specific front/rear brake combination and vehicle braking weight transfer. I would expect that you can rebuild a prop valve from one vehicle using the kit for another to get the desired prop valve.

Fitting a prop valve from a disc/drum vehicle to a disc/disc vehicle will result in reduced rear braking as disc/drum prop valves typically have a lower crack point than a disc/disc prop valve. There may also be differences in the proportioning rate once the crack point is reached.

Here are three articles on the subject.
http://www.stoptech....ng_valves.shtml
http://autospeed.com...45/article.html
http://auto.howstuff...ster-brake2.htm

[TerrA LX]

A car with rear drum brakes will have a proportioning valve with a crack pressure in the range of 150 to 250 psi.
As rear discs are not self energizing like drums they need higher pressure settings, typically 500 to 800 psi.

Anyone know where i would find a list of crack pressures for specific models?

Edited by ALX76, 09 June 2008 - 06:01 PM.

[dattoman]

Back of the PBR H86 catalogue


Did that help ?

[TerrA LX]

^ if i could get it on line, thanx Datto.

[fuzzypumper]

ALX76 , I believe the HJ HX & LH LX are the same prop valve and have a 150 crack point for the Disc/drum config. The kingswood as we all know has physically bigger brakes front and back compared to Toranas so c.p. or front to back braking ratio was the same. A HZ Disc/drum also has 150 c.p. too, but this is different because its a twin wire switch model as opposed to the earlier single wire switch. Internally the piston is different to cater for the mechanically reversed action of the switches.

On a HZ Disc/Disc (statesman) the prop valve is anodized purple and has a 450 crack point. This is done by the large rear spring in the prop valve and on this model it is 39mm long & 2mm thick compared to 27mm long & 2mm thick for the disc/drum(150cp).

I have an old VC commodore Disc/disc 15/16" combo mcyl here which has a 350 CP which I suppose its lower than HZ disc/disc due to the low rear weight of a VC commodore.
BTW. There was an A9X Combo mcyl that sold on ebay last week which had a 550 cp . Initially I thought this was high but I suppose having >100litres of full getting thrown over the back wheels everytime you braked might explain that 550cp.

Edited by fuzzypumper, 16 June 2008 - 12:54 PM.

[dattoman]

A9X and Commodore are C225
The one on ebay was a falcon or valiant master not A9X

HZ disc disc are not all purple and are different depending whether it got the "ABS" system or not

Its all reasonably irrellevant anyway
Easiest way is to get the hydraulic ratios as close as possible and then play with a manual bias valve
Simple things like different disc pad compounds or tyre size and compound change everything anyway.

[TerrA LX]

I just need a new prop valve to replace the original OEM for the standard rear drums, I have purchased one but it is not stamped, altho I do think it has a 660 crack pressure

[fuzzypumper]

When you mean new, do you mean brand new or used?
What makes you think its 660?

Here is a LX prop valve with crack point marking. If it not on the side it will be on top.

Edited by fuzzypumper, 16 June 2008 - 11:36 PM.