1carsick

Hello,

I'm looking to convert my power drum brakes to manual drum brakes. What all is needed? Can I just remove the brake booster and replace the peddle to booster rod? By the way, I'm working on a 1970 Cutlass S. Thanks,

Olds Dad

most power brake masters are larger bore inside than manuals (smaller bore diameter = higher fluid pressure for equal 'foot' force) - so, you'd have to stand on it to get it to stop...so I'd say you'll need a new (manual) master

1carsick

I had planned on buying a new MC, but wondered if any other parts were required. I thought maybe the rod, prop valve, etc.. If all I need to do is remove the booster and buy a different MC, that's easy, but I think its more to it than that. Let me know what you think and thanks for the reply.

442NDTSS

that s a good question as i have a booster and master cylinder as well as disappropriating (something like that) valve out of a 70 cutlass s and would like to install it in my 71 not power brake cutlass s. Mechanic said it was as simple as changing parts but i truly dont believe it. i remember reading somewhere where it stated all the lines had to be changed as well.

1carsick

If its that involved, I'll probably leave it as it is. I wanted to make the change before I started detailing the engine bay. Still waiting though for instructions on what's needed. Thanks,

Run to Rund

Inline Tube has the pushrod and the very important retainer which is derby hat-shaped, INL12439, 12440, or assembly 12441

1carsick

Thanks very much! I'll give Inline Tube a call.

69442C

Also and very important, when you install that new rod on your brake pedal arm, it will not go back into the same place as it was with the power booster. There are 2 holes on the brake pedal arm. For the life of me I can't recall off the top of my head if you want the top or bottom hole with a manual brake set-up. Pretty sure it's the top hole. If your power set-up is in the top hole, respond back and I can check one of my books.
Brian

1carsick

Thanks Brian. The rod for my current power drum brake is connect to the lower hole on the brake arm. Saying that, you think I should use the top hole for my manual brakes?

1carsick

Does the new MC bolt directly where the booster was? Is there any type of plate needed?
Thanks,

69442C

Let me look at my book this morning and I'll get back with you.

Just bolts to the same place. No other parts needed.

Run to Rund

The reason to change to the other (top) pedal arm hole is that you need less travel but more leverage with manual brakes.

69442C

Just verified the info and all manual brakes use the top hole on the brake arm and it doesn't matter if they are drum or disc. Power assisted go on the lower hole as yours is now.
Brian

1carsick

Thanks very much. I plan on calling Inline Tube tomorrow to check on the needed parts.

ah64pilot

I just did this conversion on my car not long ago. All you need for the change is the manual brake rod. It goes in the upper hole of the brake pedal lever (the angle is different on a power brake car, the booster tilts the rod downward which is why it goes in the bottom hole. On a manual brake car the MC is level, thus the brake rod is level and is why it goes in the top hole). It also comes with a boot that goes between the MC and the firewall.

Remove your booster and put the brake rod boot in the hole in the firewall. Then install the manual brake rod through the firewall / boot. Finally, install the MC right on the firewall where the booster was.

**I will not speak to the efficacy of manual drum brakes. I am only telling you how to do the conversion. I have front disc on my car and I used a MC for power brakes (large bore) and the pedal feel is great.**

Pictures of my conversion below:

https://classicoldsmobile.com/forums...tml#post386794

1carsick

Did you get your rod and boot from Online tube, is this something my local parts store will carry?
Thanks,

ah64pilot

I got mine from another member on here. He charged me $25 for the pair so it saved me a bit of money. He's a friend of mine that lives close so it was nothing to go get it from him. You might check with Eric (jensenracing), Brian (507olds), or John (2blue442) to see if they have one. Or you can order the ILT one and be done with it. It's up to you, but that is the only thing you HAVE to buy...and a parts store does not carry them.

If you decide to change out your MC I guess you can, but I think I remember Oh Really only having one part number...you'll have to check with them. Mine is perfect with the power brake MC, but again, I have discs up front.

Also, the only time you'll need to change the proportioning valve is if you convert to front disc brakes. They are the same for power and manual, they are different for disc and drum

1carsick

You have been a big help. Thanks to all the members.

69442C

The proportioning valve on 68-70 A Body's is the same regardless of front disc or drum. When disc's were used in these years, there was a "Hold Off Valve" installed up by the master cylinder to cause a slight delay in the front line flow to give the rear brakes a chance to catch up. Since the OP states he has a 1970 Cutlass S, he would not need to change the proportioning valve if he ever switched to front disc brakes. Beginning in 1971, GM eliminated the Hold Off Valve and had specific proportioning valves for disc and non-disc cars.

ah64pilot

Yes, somewhere along the way I thought he had a '72. I even sent a few guys his info and told them he had a '72. I don't know where I got that from lol! But yes, you are correct.

69442C

I hate it when that happens!

1carsick

Thanks to all that have commented on my question about converting my brakes. I've place an order with ILT for the rod and boot assembly. Hopefully I'll have in within a few days and I get my new MC and install it all this weekend. You guys have been a big help! Thanks Again!

junior supercar

fyi, the master cylinder is the same between power drums and manual drums. If you have the original master and you feel it's suspect, you can always rebuild it. Rock Auto has master cylinder rebuild kits.

1carsick

Thanks for the information. I'm planning to purchase a MC from my local parts store.