Gpc1

I used to own a 65 442 4speed car with manual brakes, no booster. Never had any brake issues. Fast forward to 2019 ,
currently own a 65 cutlass in which I have been restoring. When I got the car it did not have a booster. I replaced every brake component and this car was very hard to stop. Didn’t make sense everything is new. I had manual brakes on my 442 . So I got a new booster and master on there now and it stops great. Can anyone tell me what the difference would be? Just trying to solve a mystery here thanks!

Fun71

New does not always mean it works correctly. I have seen a lot of new parts right out of the box that were defective.
I would suspect the main difference was the second master cylinder that you installed.

VC455

Masters are made with different diameters. The smaller diameter masters are for manual brakes because they put out higher hydraulic pressure for the same pedal pressure. I drove my ex-brother-in law's 1970 manual disc brake W-30 many times. The brakes were easy to use and stopped well. That master cylinder was smaller diameter than the one on my 1970 Vista Cruiser with vacuum booster.

My 1970 LT-1 Corvette came with 4-wheel discs and small-diameter manual master. Those brakes were very effective and easy to use--with better feel than those with the larger-diameter master for the vacuum booster.

You supplier may have sent you a larger-diameter master designed for a boosted brake system. Without a booster, that would give you a very hard pedal as you described.

Gpc1

Thanks for the input . I know I specified manual brakes when I bought the new master but you guys are right about it maybe being the wrong one. Doesn’t matter now anyhow the brakes work great and a booster was probably a good idea too.
Thanks

MartinH

I know this is a late response but I just read this thread. On my '69 442, there are 2 holes in the brake pedal arm where the rod connects that pushes the piston in the master cylinder. The hole that is farther away from the pedal pivot is for power brakes and the one closer to the pivot is for manual brakes. Maybe the rod was still connected to the "power brake" hole?

Gpc1

Martin, I’m not sure if there are 2 holes on the 65. The new booster came with 2 different length rods and the shorter one is the one I used because everything looked correct when mounted.I believe the problem of hard brakes originated with the wrong master cylinder being used for non power brakes. Manual brake master cylinders have smaller bore diameters than
power brake masters.