I have a 68 442 convertible. I am converting the front to disc brakes. Which rear wheel cylinders should I use when I do the rears. I notice that the diameter of the rears are different from front disc and front drum. Since it was a rear drum to begin with, can I use the original size wheels cylinders, or should I go withthe ones that are for front disc??

 

Just a thought... I've read about but not done this yet. The 1976-77 Cutlass has 11 inch rear drums vs. the 9.5 of the 1968. I've been told that you can remove the backing plates and all the brake hardware, install that onto an earlier rear end as a simple bolt on swap, and have improved rear brakes. If that were done I believe the distribution block from the 76-77 would be the one to use. If your not focused on a numbers matching car and wanted a simple upgrade this would be an idea. John

 

I used Vista backing plates and wheel cylinders on my convert (for bigger brakes-but I like that idea of 11 inch brakes) and I haven't driven it yet...as for the wheel cylinders, use the disc ones if you are buying new anyway..

 

The more I look at my situation, the more I think this car might have had disc brakes from the factory, but not sure. When I got the car, the booster, master, front wheel cylinders, shoes were all missing. But the car does have a proportioning valve on the frame and the smaller "metering" valve that mounts to the master. I am wondering if someone stripped the car of the original disc brake set up. The tie rod ends were not on tight almost as is the spindles might have been switched also. Did drum brales have the proportioning valve and the smaller valve or was that only on disc brake cars? And if it is an original disc brake car, can I use the original valves instead of the one that comes with the conversion kit?

 

Given the fact there were originally several brake setups possible with your car I would think you need to do a very close comparison with a shop manual verses what you see on the car before doing anything, including attempting to put some sort of conversion disc brakes on the front. The manual will lead you in the right direction even if there is only a portion of the original brake system on the car as only certain combination's of front and rear were done.

 

If the thing on the frame is rectangular with square corners, it is NOT a proportioning valve. It is a distribution block and the same one was used on all 1968 Cutlii whether the car had drums or discs. The "metering valve" is actually an external proportioning valve used on the 1967-1970 cars before GM combined the proportioning valve and distribution block into a single combination valve.

 

The thread below has pictures of my 1968 project car brake booster. Does this look like what you have? If so then it did have disc brakes as the proportioning valve was only needed with disc brakes and not drum.

https://classicoldsmobile.com/forums...html#post82736

 

That's exactly what i have. Should I use the original parts with the new set up?

 

I think it's a personal preference, if you want to keep the original look then yes use the old setup. If that's not important to you putting on new parts will assure your brake system is completely gone through and should be trouble free. I've not looked into it, but Tangovino was able to purchase a correct new or rebuilt distribution valve for his 1970. John

 

If I use the new proportioning valve, do I need the smaller metering valve? Can that be eliminated, or use it with the new system?

 

If you put on say a 1971 setup that has the distribution block and proportioning valve as one you can remove the small valve that bolts to the power booster and you'd be replacing the block that bolts to the frame with the combination valve. John