Hey all

Does it matter which 120Y struts you put into a 1200 to get some discs on the front?

I noticed that theres to different types of 120y strut. I have some struts off a 76 model just wondering before i finish cleaning them up if there the right ones :)

Cheers!

I think the only difference is the size of the shaft that goes through the hub. i think the earlier ones are thinner than later model ones. Not to sure about it so don't hold me to it. What brakes are you running? The s13 brakes on 120y struts isn't too hard to do.

Australian assembled 120Y sedans from July 1976 used Armstrong struts with Girlock brakes. These calipers used a different piston size to the Jap brakes & you would need the matching 120Y master cylinder to make it work as the maker intended.

To add to the story, the rear wheel cylinder diameter in these models is different too. No, they are not interchangeable from the Warner rear axle assembly to the H145 or H165 Jap one.

Personally, I suggest that you stick with the Jap struts as the calipers are compatible with the original drum brake master cylinder [which will need modifying for disc brake use] & the rear wheel cylinders will match up too.

It was only the Australian assembled sedans from July 1976 that used these locally made components, all other body types were imported as were sedans up to June 1976.

Aha thanks for the help.

The wagon currently has a twin master cylinder so I should be right there for the discs with the imported struts?

If I was to go with the armstrong struts and swap over the master cylinder to the 120y one would there be any other problems? Any change to the track?

Thanks

Your wagon is probably a mid 1972 or later model & these came with the tandem cylinder. For disc brake use, you need to remove the 'residual pressure check valve' from the front brake circuit. This is the rear chamber in these tandem cylinders, but if you are going for the discs, then I recomend that you do a major overhaul on the master cylinder, or buy a new [disc brake] replacement at the same time that you fit the discs, as the unboosted disc brake system needs more line pressure to make it work [you push harder] & this could easily cause a 35 year old master cylinder to leak in protest.

There should be no problem with the fitting of the local front struts, but I highly recomend that you check ebay [& elsewhere] & buy yourself a Gregories manual for the 120Y. It won't take you long to realise that the later Girlock master cylinder & its booster will not simply bolt up to the firewall of your 1200.

Get the book as it is a goldmine of information that you can use to save yourself a lot of grief. It has a separate section devoted to these July 1976 local built sedans & the components that differ from the imported cars. The pictures within speak much more than a thousand words.

120Y ebay link
Make sure that you get only the Gregories manual [111A] as the earlier Scientific Publications version probably does not cover the later, locally assembled models

You sure do know your stuff :) Its a 1973!

I'll grab that manual like you suggest. I'll grab a 1200 one while I'm at it too. I'm sure it will come in handy.

If i was to buy a replacement master cylinder what would i ask for? A 1200 coupe one? Or is it just a generic thing?

Cheers for your help. The link to ebay is above and beyond

right, dont worry about what the factory intended the size to be...as long as you dont go heaps smaller you will be right(not that you can really go heaps smaller than 11/16ths)
i ran an unboosted 11/16th master on brakes that the factory gave a booster and a 7/8th master....still had great pedal feel and pulled up really well

i really doubt that you will have the need for a booster or a bigger master on standard 120y brakes

Quote:

dodgeman, how is there more pressure needed in the brakes lines without a booster? after all a booster only makes for less effort pushing the pedal in(just coz your pressing harder without a booster doesnt mean your doing more).....same pressure is in the lines its just easier to make it

EDIT: you want to ask for a 1200 coupe disc drum master
or if you want a bigger master ask for a sunny disc drum master
or if you want bigger again ask for a 240k disc drum master( will make your pedal a rock)
but the 11/16th coupe one will be plenty for 120y brakes

Pigdog

It's not the presence or absence of a booster that affects the line pressure in a 1200, it's the difference in the pedal pressure required between disc & drum models. The 1200 does not have a booster, so you need to push harder to create the requisite line pressure in the stock disc brake versions.

The original drum brakes are of the dual leading shoe type & this means that that they have a self servo action. The rotation of the drum actually tries to pull the brakes on harder. The actual effect is to need less pedal pressure than might otherwise be the case.

As an experiment, reverse a drum braked small Datsun at a modest clip [15kph] & apply the brakes. If it wasn't for the single leading shoe in the rears, the brakes would feel like a feather on a cannonball as there is no servo effect from the front brakes when the wheel/ drum is rotating in the reverse direction, so it will be seen that the drum brakes actually help themselves to apply when driven in the forward direction.

The front discs, on the other hand, simply clamp the rotor between the pads. There is no servo, or self applying function, & all of the effort must be provided via your right leg.
Keep in mind that the master cylinder is the same bore size as the drum brake one & it isn't too hard to see how it all works. This is why the coupes used a smaller bore rear wheel cylinder. The higher line pressure in the disc braked coupe was leading to rear wheel lockup, particularly in the wet, so a piston with a smaller surface area is used to reduce the braking effort at the rear at any given line pressure. Since the system now has more line pressure than in a drum brake system, the balance is restored.

A smaller bore master cylinder will supply more line pressure for a given pedal pressure, but the amount of piston [& pedal] travel will be greater for a given amount of fluid displacement. It's all a matter of balance & if the rear brakes are adjusted regularly, & properly, then the smaller bore cylinder will be a bonus.

so a simple reply there being, sorry i wrote that wrong.....i meant that there is more pressure needed in an unboosted disc drum system than a drum drum system

could save yourself some typing next time

Yes, you are probably right, but the response will hopefully be of some use to other members with less experience.
Well, that's my excuse.