Boredom New Reader
6/3/21 6:18 a.m.

Hi all,

Sorry for all ignorance moving forward from me.

I recently purchased a 1966 olds 98. Plan for it is to turn it into a weekend cruiser for now. On it is the original single reservoir master along with drums all around. The drums in front I am fixing using a scarebird kit but now i am questioning the master cylinder. Of course I need a duel reservoir set up for drum and discs, while there are an ungodly amount of options I am just hesitant due to the original power brake system. So my question (and do tell me if I am not asking the right one!) is will any master that can mechanically fit/mate to the booster work with it? or is there more to it than that?

One option I am considering is upgrading to the newer generation duel reservoir master below with my stock booster, this plays into "if it can physically mate to booster will it work?" thought....

Summit has the following kit too.

it is designed for pontiacs, chevys and olds (cutless,442) of that generation so even though it does not list the 98 as one of the options maybe it is a contender and I wont need to worry about my master/booster combo? (I know kit does not come with proportioning valve) Maybe I am over thinking all of this? Brakes just make me a little nervous sometimes.... 

Thanks in advance!

wearymicrobe PowerDork
6/3/21 10:16 a.m.

In reply to Boredom :

It has been my experience with conversions that when the master like the one posted has a much larger front reservoir that it is setup for disk/drum not drum drum. Which you can see in the notes. This will not work on drum drum without some form of proportioning valve. Someone else might have a better drum/drum kit for you or at summit, the getting it to fit part of the equation is the hardest part. 


Designed for models with front disc brakes and rear drums.



Boredom New Reader
6/3/21 10:39 a.m.

Sorry, should have been more clear. I am upgrading the front to disc using scarebord front conversion brackets so it will be front disc rear drum set up. 

ShawnG UltimaDork
6/3/21 11:01 a.m.

If the new master bolts to the existing booster, you will be just fine.

Why not ask Mr. Scarebird what M/C he would use with his system?

Good on you for trying to use OEM components like that. Most folks want to upgrade to some goofy aftermarket setup that will probably be out of business the next time they need parts.

L5wolvesf HalfDork
6/3/21 12:09 p.m.

I am in the process of doing a front disc upgrade on one of my projects. There are some easy calcs here to help determine what you should need. 

There is no need for calculations and don't overthink this. Go to NAPA and get an MC for a 67-70 Olds 98 with disc brakes.  Yes, there are other applications for that MC, but this is the simplest route and you will end up with the right MC.  I also agree with asking Scarebird, but they should give you the answer I just did. 

Also, know that 4 wheel drums will work just fine with a proper rebuild with quality parts and proper adjustment, especially if it's just a nice easy cruiser. 


Edited to add: Olds used 14" wheels on those cars, even the '98's, and offered 15's on disc brake casr starting in '67. If you still have 14's, you may have an interference problem. 

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