2229171 1" bore Master Cylinder

[Ramman]

I have an early production, LA built, 70 Challenger R/T with power disc front 9" rear drum brakes. It has the correct 2229171 1" bore master cylinder thats in need of repair. I notice that the later Challengers and Hemi cars with this brake setup changed to a 1 1/8" master cyl. If I'm not concerned with correctness, will the bigger bore master cyl. improve braking or should I look into having the original rebuilt? My thoughts are the bigger bore will move more fluid but increase pedal effort. Which may not be an issue with power brakes.
As a side note, I could probably buy all my body supplies for what 2229171 cores are bringing.

Thanks group!

[Katfish]

[JH27N0B]

I used to be an engineer at an aftermarket brake manufacturer and still never figured out the reasoning on different bore size and piston stroke, sometimes on the same model.
70 E bodies used a 1" bore MC on power and manual drum brakes. And a 1" MC on disc brakes.  But a 1-1/8" MC on disc hemis. Same hemi disc MC on B & E.
In 71 they went to using 1-1/32" bore MCs on both B and E bodies. And both drum and disc.
With my Challengers I've used a number of different ones. All my E bodies have been disc brakes.  One car had an aftermarket 1-1/32 when I bought it and it stopped fine.  Another car had an original 1" 9171 on it. When I replaced it after it failed, I put an aftermarket 1-1/8" mc on it.  The pedal was harder and I noticed a few times when I braked hard, the rear brakes started to lock up before the fronts.
I later rebuilt the 9171 and put it back on, and now the brakes are fine again.
My 71 has an original 1-1/32 on it.  It stops fine.
So if I was going to replace a MC on an E body and didn't care if it was OE, I'd use the 71-74 1-1/32" MC.

[Ramman]

I knew it wouldn't be "necessary" to go up in bore size. Just thought while a replacement was in order, could I improve performance by upping the bore size? What caused Chrysler to? Did they change caliper piston size as well?

[JH27N0B]

Calipers were same across the board in 1970. And in subsequent years effectively the same caliper but some minor differences and casting number.
They used the same master cylinder pretty much across the board for drum brakes from 67-70 on all models, A body through C body and even some pickups, but a bunch of different disc brake master cylinders.
I'll probably never know why.  But from personal experience both the 1" disc brake from 70 or the 1-1/32" from 71 through 74 work fine on a 70 E body.