C-3 Master Cylinder ID

[Bill Lloyd #33481]

I have a '72 Base engine Conv. with std brakes. The casting number on my current master cylinder is 29969 and no bleeder screws are present. In addition, I have a replacement as well. It is configured identically and is Casting number 5460346. The JM does not specify the correct casting numbers for master cylinders. What is the correct casting number for my car? What are the above casting numbers for?

Thanks
Bill

[Gerry Proctor]

Re: C-3 Master Cylinder ID

The "346" Master cylinder is for a power brake car (not necessarily a Corvette either). You cylinder should be a "5455509" casting. The casting you have is just a parts counter (likely a Wagner) replacement casting. And if you more closely examine the cylinders, you'll see that the 346 cylinder has a 1.125" bore while the replacement casting for a non-assist car has a 1.0" bore. A correct-appearing 1972 cylinder will also have the bleeder screws above the outlet ports. You can use a 346 casting on a non-assist car as long as you change the piston to the deep-well pushrod receiver design. You will have to use more pedal pressure for the same piston pressure with the larger bore cylinder. I also have a non-assist '72.

[Jack H.]

Yes it does....

Look at Mechanical, Section 17, Brake Master Cylinder & Power Booster, page 72 of the current '70-72 Technical Information Manual and Judging Guide. I think you'll not only find the casting numbers called out but the other identifiable features of know factory original master cylinders from this era defined (front and side boss machining, emboss marks, bleeder screws, cover and broadcast ID tag)....

[Bill Lloyd #33481]

Re: Yes it does....

I missed it right on page 72. Thanks, I stand corrected.

Bill

[Jack H.]

You found it--way cool!!! *NM*