NOTDADS

I have a headache trying to read all the info on disk brake conversions. haha. Hopefully someone has done my particular setup and know's what I need. I have a 70 Cutlass S which origionaly had power drums all around. I bought a Baer kit and replaced the front drums with discs. Everything fit great and looks pretty but doesnt stop worth diddly. Sometimes it's hard to even get it to come to a complete stop. Pedel pressure seems fine but it just doesnt want to stop well. I have a power booster and dual reservoir MC that runs down to a brass block on the frame and then to the brakes. From what I understand is the 70' 4 way drum had a distribution block and no proportioning valve. What I'm confused about is when I look at the distribution block it looks exactly like a proportioning valve that I see online. 2 in, 2 out, and a fitting that I believe is for the brake warning light but I can't see it all that great from up top. Anyone know what I need to get it right?

2blu442

Hi Matt
The 1968-70 proportioning valve was a small valve attached to the power booster. In 1971 and newer there was a proportioning valve that replaced the distribution block on the frame with a combination distribution/proportioning valve. So make sure you either replace the frame mounted piece with one from 1971 or 72 or get the 1969-70 proportioning valve and mount it with the factory bracket/lines on the booster. One more thing that I'm not positive about but have read that the power booster rod for drums is different than disc. This is the rod that moves from the power booster into the master cylinder. Try some additional searches on this site as I know there have been several threads talking about this. John

NOTDADS

Cool, thanks for the info. So I "should" be able to just swap out the block on the frame with a "proportioning" unit from the catalogs and be in business. I'll order one up and give it a shot. I have read that the plunger is bigger on the MC. Do you know if the lines are the same? I can get a new MC to if that's what it takes. Just not sure if I need to order new lines too. Hmm.

2blu442

Yes, install the disc brake combination valve. I just read back through your post and wanted to make sure you have a disc brake master cylinder. The drum brake one has two reserviors that are the same size. The disc has a larger reservoir in the front and a much smaller in the back. I also think you may have to change some of the brake lines. If my memory is sharp enough I believe the drum is all the same size but the front disc uses a larger size fitting/line than the one for the rear drums. Give that a try and let us know if that fixed your problem. John

NOTDADS

Cool, thanks! I'll work on it this weekend.

NOTDADS

I received an email from a company called inline tube and they say that for my setup I only need add this hold-off valve listed below and the 5 piece front end line kit for a 70 cutlass with front disks.
http://www.inlinetube.com/Prop%20Valves/PR-115.htm
They say another option is to install a later model combo valve under the MC and a new line kit to bypass the distribution block that I have. Does anyone know if there is an advanage to the later model combo unit? I seem to recall that the distribution block sent equal pressure to all 4 wheels and disc brakes needed more, but it seems that in 1970 they just used the distribution block and hold-off valve.

NOTDADS

Well, I was just crawling around outside in the dark with a flashlight because I always get off of work so late. I think I may have found the problem. I didnt even think you could do it but it looks like I actually have the front brake line going to the front(small) chamber of the MC and the rear brake line going to the rear(large) chamber. Correct me if I'm wrong, because perhaps I didnt buy the correct MC, but the large chamber towards the firewall is for the front brakes which should be the larger diameter brake line, and the smaller chamber towards the front of the car should be the thinner brake line for the rear. Is that correct? I have them flopped.

2blu442

Hello Matt
I don't have any experience with non-stock proportioning valves. Maybe some of the other guys can comment on that. The larger side of the reservior should be closest to the bumper and the smaller side closer to the firewall. I believe there should also be different sized fittings for the front and rear on the disc brake MC to prevent that from happening. John

NOTDADS

Thanks for the info. I must have the wrong MC then because on mine the large reservoir is in the back. Dangit, it's always something. haha I'll see what the parts store has available this weekend.