70cutlass831guy

Hello Oldsmobile enthusiasts,

Im am currently in the process of converting my 70 cutlass S coupe from manual front drums to power disk brakes. I have aquired most of the front components to do this swap from a 72 cutlass coupe (non fast back). The master, booster, and complete hubs with calipers and lines.

I know there has been threads and thread this on this topic but I have not been able to find the answers to my specific questions also these are my brakes and I dont want to chance doing somthing wrong and getting into a crash.

First question is can I use the same combination valve from my manual front drum brake with the new boosted disk brake set up?? or would I need to have the combo valve from the original donor car?

Second question is I know the steel brake lines that go from the master to the combo valve are two different sizes. my previous lines were done poorly and routed terribly. What size line goes to what port on the master and from the master to the combo valve?

The help is greatly appreciated and Thanks

oldstata

The proportion valve needs to be changed to a disk set up I would pull from the doner car

70cutlass831guy

Thanks for the info.

oldstata

You can look up right stuff brakes they have prebent lines . I know there's other that have them ,just a thought they are a fair priced considering the time it would take to do your own, unless you like the hobby part of doing it your self .

70cutlass831guy

I am the hobby type and have already made the new lines (haha) It wasnt too bad time wise. I had all the tools to do it so I figured what the heck. Thanks for the good info ..

70cutlass831guy

Thanks for the complete brake down Joe. for some odd reason I cant see your reply on this thread on the computer but it did show up in my email.

I know its anoying to answer the same question over and over again. Thanks for your patience.

oldstata

Pics are needed 😸

70cutlass831guy

I found a prop valve on OPGI for 70 bucks shipped. Should be here in a few days. we will see how it goes. Part ID= CH26775

Maverick

Starting my swap tonight. Wish me luck.

70cutlass831guy

Nothing to it. Start a thread take pics.

70cutlass831guy

I am going to post pics real soon.

oldstata

Good luck

70cutlass831guy

The OPGI Prop Valve came in. Looks pretty good to me. The only problem I am having is finding the Brake line fittings. None of the parts places seems to have the right fittings I need. I will track them down.

I am going to mount it under my master as the box suggested. Has any body used this OPGI Prop Valve?? If so is how did it work?

oldstata

Are you redoing the brake lines or just looking for adaptor fittings ? If you are looking for adaptors I wouldn't suggest doing it I believe the line size is different

oldstata

http://www.getdiscbrakes.com/akt7003

70cutlass831guy

I am looking for the fittings with the right size line holes then I will be making lines from the Prop Valve to the existing lines with double female ended adapters with the right size hole. I already found the front line double female adapter in 3/16 with the right thread all I need now is the 1/4 double female adapter and one fitting 1/2 fine thread with a 3/16 line hole and I should be set.

70cutlass831guy

Nice Thanks for the link.

joe_padavano

Most better-stocked auto parts stores have these adapter fittings. Unfortunately they are not frequently sold so most counter jockeys don't even know the parts are in the store. I've had good luck with both NAPA and AutoZone. Also, AutoZone has the flare nuts with different thread sizes in stock, so if you are making lines, avoid the potential extra leak point of the adapter and just use the correct flare nut to start with. Usually you have to paw through their drawers of fittings to find these parts.

Note that GM used flare nuts with different size threads to prevent incorrect brake line connection on the assembly line.

70cutlass831guy

Yeah the parts guys have no idea where to even start looking they just point to the fittings case and say " Good luck thats all we have".
I have two mounting choices with this prop valve . 1 I can mount it under the master as the box instructs me to and add two more lines and double the fittings or 2 I can mount the prop valve on the frame rail where the original was and trim the rear 1/4 line and re flare it (since the new prop valve is longer) but I really dont like the idea of trimming the stock rear 1/4 brake line. What would you suggest?? I think trimming the rear line would be the easier route but once its cut theres no going back and thats what I dont like.

oldstata

Was factory disc mounted on the frame ? Or just factory drum ?
I personally like the look of it mounted to the booster/master cylinder

70cutlass831guy

Both the disk and drum prop valves were mounted on the same spot on the frame rail. I dont care about the look I just want it to function porperly.

Maverick

Wow, what a pain in the *** . JUst having trouble bleeding brakes now.

Octania

PITA?
Heh, if it was easy, ANYBODY could do it!

For correct fittings, how about using the ones off old cars? There's a few of those around.

70cutlass831guy

What about it was a pain for you?. For me it was just finding the right fittings for the Prop Valve. What bleeding method are you using?

70cutlass831guy

there really isnt a lot of parts cars around here.

Maverick

Prop valve larger than old one. New brake lines now to long . No easy method to connect to prov valve once installed. No skin left on knuckles or top of hands. Almost impossible to remove booster. Can be done, just takes a ton of time, 1/8 " at a time. Not much I guess.

70cutlass831guy

Was your new disk brakes from a kit? or from a donor car? I am having the same problem but only with one line.

Maverick

Kit

70cutlass831guy

t

Thats what I hate about kits. There is always somthing wrong with them. I have yet in my life recieved a "kit" that I didnt have to adapt to fit in one way or another.

70cutlass831guy

Update:
So after looking and looking for this non existant fitting I gave up and this is what I plan on using. 1/2 by 20 flared adapter to 3/16 fitting. In the first picture you can see the original fitting I cant find and the adaptation I will be using. Now I have all the parts to complete the disk brake swap. wish me luck. I will doing the rest of the swap this weekend. Ill post more pics and steps.

joe_padavano

Here's your non-existent fitting. $2.99 from Summit. This was just the first place I looked. AutoZone lists them under part no. BFLX-41.

http://www.summitracing.com/parts/aa...0114/overview/

70cutlass831guy

Thanks Joe. I had found it online I just didnt want have to wait on shipping. I tried 2 Napas, O rileys, Skips auto parts, and Brake supply with no luck. I will try autozone with the part number you gave me.

fourtwenty

I found one off a 70,s era van on the master cylinder
cheers Orrick

70cutlass831guy

The one place I didnt check and sure enough they had a box of them (AutoZone). The part number was a few characters off. Part number BLF-41C-5
Thanks Joe

Maverick

My brakes are worse now after the swap. Soft pedal . Wondering if my vacuum is to low because of the cam . Don't feel real comfortable driving it now. Re-bled MC and all wheels. No change . Any ideas ? Will run it by the local garage tomorrow to check vac lift.

70cutlass831guy

I have bench bled Masters and some take more then others to get pressure to build up. what bleding method are you using to bleed the brakes? Are you using the right bleeding sequence? do you still see foam or bubbles coming out of the bleeder screws?

joe_padavano

Low vacuum would make the pedal harder, since it means that you wouldn't have much power in the power brake booster. You still have air in the system.

Maverick

Air or not. I still only have 10" of vac lift .Just found that out. More bleeding it looks like. Wonder where it is ? Not getting bubbles anywhere .

oldstata

I like to bench bleed the master as well as on the car have a buddy put pressure on the peddle as you crack the front then rear brake lines close the line before releasing pressure some times air get trapped here

70cutlass831guy

Agree X2