How to make a 3/4" JZA80 clutch master cylinder.

[AndyTTR]

The standard JZA80 clutch master is 5/8" bore, this is not enough for most Hydraulic Release Bearing (HRB) conversions which require a 3/4" bore. I believe there is a Tilton M/C that bolts up, or you could find a place to re-bore and sleeve the stock M/C but these options can cost a few hundreds of dollars (if you could find a place to do the work at all).

I started a thread asking about re-boring and Big_Zop mentioned that an older Landcruiser (40 series I believe) shared the same flange as the JZA80. This got me thinking, surely if one Landcruiser had this flange others probably do too? Long story short, after much trawling I found that the M/C from a FZJ75 / FZJ80 Cruiser had the same flange and a reservoir which could be swapped for the JZA80 one. Best bit is, this cost a grand total of $30 from my local 4x4 wrecker!

Step 1: Aquire FZJ75 or FZJ80 Landcruiser clutch 3/4" master cylinder. You're looking for the variant without the flange to suit a booster or a built-in accumulator (that cylinder that screws in the bottom). The following picture shows the JZA80 (bottom) and FZJ80 (top) master cylinders side by side.



Step 2: Disassemble the 3/4" and 5/8" master cylinders. Remove the retaining cir-clips and swap the push-rod and clevis from the 5/8" master to the 3/4" master cylinder. Reassemble the 3/4" master cylinder.



Step 3: Knock out the retaining pin and swap the reservoir from the 5/8" master to the 3/4" master. You'll need to make some kind of support for the longer JZA80 reservoir to ensure a good seal. I used a bit of scrap steel and held it in place using cable ties.



Congratulations, you have a 3/4" JZA80 clutch master cylinder!


Step 4: Installation

Basically your new 3/4" master will bolt straight in - no mods required to the pedal box or firewall. You will however need a bolt for the lower hole in the flange as the Landcruiser master cylinder doesn't have a stud like the Supra one. I used a hex-head shoulder bolt to make installation a little easier.

The only other significant mod you will need to do is to is to cut and re-flare the hard pipe to suit as the outlet on the 3/4" master is on the opposite side to the original one. If you were really clever you could source a 3/4" clutch master from a left-hand-drive country with the outlet on the same side as the original, but as my car is non-turbo I had plenty of space to play with. Alternatively you could make up some kind of adaptor, but that'd look pretty messy...



Bleed it and you're away! Hope this helps someone, info is pretty scarce on this topic.

[dnegative]

Bleed it and you're away! Hope this helps someone, info is pretty scarce on this topic.

Awesome, +1 rep

Thanks for giving it a go, there was quite a bit of info on clutch master interchangeability on toyotacressida.net (its essentially a DIY manual conversion using whatever you can find) but its no longer with us. From memory the majority of master cylinders are essentially the same sort of design bar the bolt spacings (only two types, one is symmetrical they other is not) bore and fluid reservoir shape. I had a feeling you could swap the reservoirs around.


+ they can all be had new pretty cheap, I got a new "asin" JZA80 master off eBay for like $80 shipped and have picked up AW11 ones for about the same.

[Bazda]

Awesome write up Andy, i've included it in my forum thread.

[AndyTTR]

Cheers guys!

dnegative - That's interesting... are there many 3/4" master cylinders with this sort of flange? I had a look through the ATAP catalogue and the only ones that came up were for Landcruisers or Alfettas? If there was one with the same flange and reservoir but with the port on the other side that'd be ideal!