27 replies to this topic

[REDA9X]

they look right to me, maybe it's a problem with your master cylinder setup, Dattoman would be able to help

[dattoman]

If he hasn't taken it out since the discs went on... spot on Rory
Pipes are the right way round

[dattoman]

Larger threaded outlet is rear brakes

[fuzzypumper]

There is something very wrong with SLR253's photo or I'm seeing things.
He is feeding the front brake tank of Master cylinder into the rear brake section of the proportioning valve. Anyone else see this?
Dattoman?
You must be locking up the rears?

In reference to PBR Master cylinders used for DISC/DRUM setups, the LH's had the P7210 which had the large tank for the front brakes towards the front as RORYMS pic shows.
Unfortunately as Holden did with a lot of their parts they also used this master cylinder on the first 9 months of LX Torana (till Dec 76).
Then they changed to the P7369 Master cylinder which has the large tank for the front brakes on the back(at the vaccum bosster end) all the way till the UC too.

[dattoman]

PBR went to one casting so which section is larger has no relevence anymore

The large nut is the rear
Simple as that

[Dr Terry]

Hi dattoman

On that same topic, did all HQ-HZ PBR alloy master cylinders have the larger flare nut at the rear.

Does that mean when you fit one to an HZ or a late HX, late LX or early UC, that you need to bend the brake pipes to suit (i.e. swap front to rear).

The late larger GM-H cast iron m/cyl, fitted to those models had the larger flare nut at the front.

It's been so long since I fitted one, that I cannot remember.

Dr Terry.

[fuzzypumper]

Dattoman,

Yes agreed at the M/cyl the larger nut 9/16(larger threaded hole) is the rear brakes and the smaller nut 1/2"(smaller threaded hole) is the front brake but I still think SLR253's pipes are wrong way around, how? well I suspect the pipes he has are madeup ones as they dont have the original factory bending and running position and where made with opposite fittings. So they can only be plumbed one way, the wrong way.

Not sure what you mean by one casting ????
I still believe the cambers are different as piston chamber sizes are also different as well as larger tank capacity for front brakes to cater for larger front disc caliper pistons compared to rear.

I also suspect the front brake chamber was switched to the rear of master cyl on the later M/cyls to ensure a mechanicaly direct connection between pushrod. On the older ones the front brake m/cyl piston was pushed under the pressure of the spring from the rear piston.
If this spring was tired or broken or front piston was siezed only rear brakes work. Off course I may be overthinking the issue.

Dr Terry.
I had to bend pipes around to fit reversed later tank m/cyls as well.
Some early HQ or LH have had the older P66xx series which are arent as tall and have smaller capacity tanks but where still a 25.4mm bore.
P7210 & P63xx have front brake tank towards front (smaller 1/2" nut).
P7369 have front brake tank towards rear (smaller 1/2" nut)

Below info is from PBR catalogue:
HQ 07/1971 - 09/1974 DISC/DRUM, WITH MVAC, 25.40 mm P7210
HJ 10/1974 - 12/1976 DISC/DRUM, WITH MVAC, 25.40 mm P7210
HX, HZ 01/1977 - 12/1980 DISC/DRUM, WITH MVAC, HX MODEL, HZ MODEL, 25.40 mm P7369

LH 03/1974 - 02/1976 DISC/DRUM, WITH MVAC, 4 CYL, 6 CYL, 8 CYL, 25.40 mm P7210
LX 03/1976 - 12/1976 DISC/DRUM, WITH MVAC, 4 CYL, 6 CYL, 8 CYL, 25.40 mm P7210
LX 01/1977 - 03/1978 DISC/DRUM, WITH MVAC, 4 CYL, 6 CYL, 8 CYL, 25.40 mm P7369

Edited by fuzzypumper, 08 January 2008 - 11:12 AM.

[dattoman]

PBR used to cast the cylinders P7210 and P7369 as 2 different units with bowls corresponding
Large to front small to rear
However as a cost saving measure they went with one casting ... cheaper that way
they just drill and tap the outlets as needed
Rear port size is always the larger one
Regardless of bowl size
They are all 1" bore... no differences there

[fuzzypumper]

Ummm I have pictures.
Rear nut is not always large for both models, however the large nut is always for the rear brakes and follows the position of the smaller tank.

P7210


P7369

[dattoman]

Ok for the 4th time
Large port rear brakes
Regardless of what the cylinder looks like

[fuzzypumper]

We are both right.

I just came back from Cruizin car show at Knox Ozone and I did see a few toranas with P7210 Mcyl with the large nut tapped into what I call the the front brake tank which is opposite to the the one I have at home.

I dont know what PBR where thinking ?????????-

[Dr Terry]

What is the purpose of removing the brass plug from the master for the rear brakes if you have Vn disc's? Just to send more oil to the rear for more braking force?

Hi DOG355.

It's not really a plug, it's an olive. Also you don't remove it & just throw it away.

What you need to do, if converting to discs, is to remove the olive & then remove & discard the little rubber valve insert (& spring) inside & then refit the brass olive. This rubber valve insert is the residual pressure valve & is not required for discs, it's only used for drum brakes.

If the brass olive is not there, the flare at the end of the pipe will have nothing to seat against.

Dr Terry