Hello,

To begin with, the stock brake system is just fine as long as everything is in good condition including the parking brake cables.

The 1968 122/1800 dual circuit arrangement is pretty much standard in the automotive industry for cars without ABS, except for the fact that the "hydroboost" type of brake booster that was used at the time only boosts the front circuit.

There are many ways to convert, some are more involved and some are simpler.

For the simplest dual circuit conversion that can I suggest, use the following parts and techniques.

If necessary, get the calipers rebuilt and rebuild or replace the rear wheel cylinders.

If necessary, get an original style "hydroboost" brake booster rebuilt. If you do not have one, you should get one.

Check and if necessary replace all 3 brake flex hoses.

For a brake master, use either the bolt on dual circuit brake master for a 1968 122/1800 from CVI which will need a reservoir, or use the replacement brake master kit for the 1968 brake master, which might also need a reservoir.

For the warning valve/splitter, find an original warning valve/splitter or use a Volvo 240 warning valve/splitter.

If you use the Volvo 240 version which are available new, you will have to plug some of the extra ports.

Install a very simple brake imbalance warning light system.

You will have to re-route the rear brake line from the junction at the firewall to the warning valve/splitter and plug the open port at the firewall junction.

You will need to make a few brake lines or connections from the master to the warning valve/splitter, from the warning valve/splitter to the booster and from the booster to the firewall junction.

The result will be as near to a modern dual circuit system as you can get without going to a modern booster/master setup where the booster pushes on the back of the brake master and therefore boosts both circuits.


--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502