72 Master Cylinder ?
Thread Starter
Intermediate
Joined: Sep 2003
Posts: 38
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From: Arlington Tx
72 Master Cylinder ?
I've been getting conflicting information on an original brake Master Cylinder for a 72 vette with power brakes. I see that one restoration guide shows
it to be casting# 5480346 with a "PG" or "MK" satmp on it, but some of
the vendors with cores say it is #5460346 and can have no marks at all
and still be correct? Can anyone clarify this. One vendor tells me that all
346 castings are the same? Looks like maybe this casting is used from 67
on up through 72? CDC
it to be casting# 5480346 with a "PG" or "MK" satmp on it, but some of
the vendors with cores say it is #5460346 and can have no marks at all
and still be correct? Can anyone clarify this. One vendor tells me that all
346 castings are the same? Looks like maybe this casting is used from 67
on up through 72? CDC
Team Owner
Joined: Aug 2000
Posts: 21,457
Likes: 463
From: Massillon,Ohio USA
2020 C3 of the Year Finalist - Unmodified
Cruise-In VI Veteran
St. Jude Donor '08-'09-'10-'11-'12
Re: 72 Master Cylinder ? (cdc)
Yes, it still can be correct. This is one of those items that some were stamped, some were not. Same way with the dates on these. Some were dated by the factory, some were not. I do know '68-'72 PB cars were the "346" casting and DID HAVE the "bleeders" on them The main thing is for it to be the "346" casting AND have the bleeders.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Re: 72 Master Cylinder ? (mrvette)
The "346" power brake cylinders (either number prefix) are 1.125" bore and that's about as big a bore as you can get on the "General's" master cylinders. Also, as bore size changes, so does line pressure for a given pedal pressure so you better have some idea what you're doing here or it's pretty easy to put yourself in the trick bag. On Corvettes, the manual brake cylinders are 1.0" bore (the typical "509" manual cylinder with bleeders). This is for the outside of factory correct but none the less some good info for the C3s: Bleeders on the cylinder were used on all master cylinders through 1972. All manual cylinders were 1.0 bore and power cylinders were 1.125". All master cylinders, power or manual, though 1976 used a deep piston well and required a corresponding length pushrod, which is a consideration when power booster shopping. After '76, the piston design changed to a shallow well (essentially not much more than a divot in the receiver on the piston). You can use a power cylinder on a manual car and vice-versa but this is not recommended since pedal pressure for a manual car using a power cylinder can be quite high and brake sensitivity for a power car using a manual cylinder can be too touchy.
