1938 master cylinder

[Pete Phillips]

Finishing up a '38 Special restoration, but the master cylinder has a crack at the end where the threads are so it leaks badly. So far, I have only found badly weathered, rusted ones. I know rusty ones can be re-sleeved, but Dave Tacheny has warned me that the one he is sending me is really bad.  I have just found a new old stock one for a 1937-1938 Century--don't have it here yet. I assume the mounting bolt holes will be the same and the only difference may be a larger diameter for the cylinder's bore. Is there any reason why I could not use a larger bore master cylinder on this Special? I realize it will probably push more fluid per pump, and therefore the brakes may act a lot quicker, but what's wrong with that?

 

Pete Phillips, BCA #7338

Leonard, TX

[wmsue]

When I installed disc brakes on my 65 Buick, the brake pedal was a lot harder (especially cold) than before. And did not go down much when pressing on the pedal.

The factory setup original M/C dia was 7/8" and I believe the replacement was 1 1/16". The stroke was the same.

The disc brake setup never failed me but after converting back to factory setup, I liked the feel of the pedal better than with the disc brake setup.

 

Here's an explanation from google:

"The diameter and length of the master cylinder has a significant effect on the performance of the brake system.

A larger diameter master cylinder delivers more hydraulic fluid to the caliper pistons,

yet requires more brake pedal force and less brake pedal stroke to achieve a given deceleration."

 

 

[Fireball8man]

Pete:

 

The 1938 Buick Special Master Cylinder ONLY fits a Series 40 ONLY.  The larger series 60-80-90 Series will not interchange nor mount the same.  PS: Just ask Dave who sold you the Series 40 Master Cylinder, he will say the same thing.

 

Lawrence

[Bloo]

With a larger bore the pedal effort required to stop the car will be higher, probably a lot higher.