Series I 330GT Brakes

I’ve been pulling my hair out on a SI 330 brake system and I need the help from other SI 330 owners. What I basically need is someone with a SI 330 that has his Master Cylinder out of their car so they can measure the bore of the Master cylinder. They’re usually in inch measurements 3/4, 7/8, 1-inch, etc. It’s important to note that I need a M/C from a SI 330 with a dual circuit master cylinder designed to work with a dual booster set up. Ferrari only used this set up for less than 400 cars before installing hung pedals with a mastervac system.

I’ve rebuilt the brake system on this SI 330 and at the final stage of bleeding, the pedal moves a lot more than it should. I can get boost, but there is just too much pedal travel. This car came into the shop with a failed master cylinder, so it’s hard to know exactly what the brakes felt like before I rebuilt the whole system. I’ve tested the boosters and they’re working correctly with the right amounts of input and output pressures on the gauges. We suspect the M/C was changed on this car with a similar external dimensions but a different internal bore. With an incorrectly matched M/C, it may be the cause of my problems.


If you have any information on the correct size of the master cylinder, you can respond at the forum link:

I’ve rebuilt a couple power brake systems in the last year or so and have been learning a lot about how to test, diagnose, and rebuild these units, but this one car had been the death of me. I know I’ll eventually figure it out, but really could use some clues to figure it out!