Brake Boosters and Master CylindersBoosters
1967-69 Camaros used Delco Moraine brake boosters. The application code for the booster is stamped on a tab on the top right of the booster (see picture below) and the Julian date is stamped on the other side of the tab. In 1968, both the drum and disk brake boosters changed to new part numbers during the model year and both codes are listed below.
1967-69 Camaros used Delco Moraine master cylinders. The casting number is on the the side or the bottom of the master cylinder. 67-69 manual drum brake cars used the 5452310 casting except 1967 cars with manual J65 brakes used the 5461862 casting. Power drum brake cars used the 5460465 casting. 1967 manual disc brake cars used the 5459467 master cylinder casting. 1967 and 1968 power disc brake cars used the 5460346 master cylinder. Early 1969 disc brake cars also used the 5460346 master cylinder (for about a month or so of production) with later 69 cars using the 5468309 casting.Power drum and power disc brake master cylinders were installed at an angle and trapped air in the bores of the master cylinder. Bleeder valves were installed to allow this air to be purged from the system. The manual disc brake master cylinders were installed horizontally and did not have bleeder valves. We believe the manual drum master cylinders also did not have bleeders, but there is some conflicting data and this is still being researched.The application code for the master cylinder was stamped on a small pad on the front of the casting, as shown in the sketch below. Note the tag with the broadcast code also shown in the sketch. The broadcast code and the master cylinder application code are not the same; the broadcast code is for the entire assembly and the application code is for the bare master cylinder.1969 J52 disc brakes used the US-stamped master cylinder. 1969 JL8 four wheel disc brakes used a similar master cylinder, though the stamped code is unconfirmed at this time. The only difference between the master cylinders was the J52 master cylinder had a check valve in the outlet for the rear drum brakes, whereas the JL8 master cylinder did not have any check valves.
Bore 1967 1968 1969 Size ---- ---- ---- ---- Manual drums * BS/CT BS BS 1" Power drums * BS BS BS/CT 1" Manual J65 drums AU - - 7/8" Power J65 drums ?? - - 1" Manual discs AD - - 1" Power discs WT WT US 1 1/8" JL8 4-wheel discs - - ?? 1 1/8"
* Most drum brake master cylinders are coded BS. But a limited number have been observed with the CT code, in both manual and power drum applications. It is unknown why the CT part was used (possibly a substitute during a parts shortage?) and if there are any differences between the BS and CT master cylinders. The CT code is shown in the applications observed so far.
Rear Brake Line Pressure Regulator Valve UsageAlthough we continue to research the usage of this valve, this is a summary of what we know so far.
On certain Camaro models, a two-piece rear brake line with a brake pressure regulator valve was utilized. This valve mounts on the rear of the front subframe under the driver's door.
On Camaro models equipped with air conditioning, the rear brake hydraulic line is routed through a pressure regulator valve mounted on the left frame side rail (fig 3). The valve controls the hydraulic pressure to the rear brakes resulting in the correct pressure balance between the front and rear hydraulic systems.The November 1969 Chevrolet Service News adds the following (note that by 1970 the emphasis in the description was on front disc brakes, though the valve was also used on certain 67-69 drum brake cars):
The valve limits the amount of hydraulic pressure, at a controlled rate, to the rear wheels in proportion to the amount of pressure to the front wheels. ... This action prevents the rear brakes from locking up before the full effective braking effort is produced by the front disc brakes.The implicit rationalization in the 1967 description was that the valve was needed to improve stopping due to higher front end weight resulting from the C60 air conditioning equipment. Restricting use to C60 is suspect logic; there were other options that added the same (or greater) front end weight. For example, in 1967, an otherwise optionless L6 with C60 would get it, while a RS/SS350 with smog, power brakes, and power steering (but no C60) would not get the valve, despite having a higher front-end weight.Valve Usage
Usage of the valve was not consistent.
- 1967 Camaros that received the valve were: all models with C60 air conditioning, all SS396 models, and NOR-built Z28's (at least the later ones). However, the 1967 LOS Z28's did not get the valve.
- For 1968, only cars with 12-bolt axles received the valve. The C60 air conditioning option no longer caused use of the valve (though C60 cars could get the valve due to a 12-bolt axle). The one known exception is that NOR Z28's stopped using the valve midway through the 68 model and didn't begin again until mid-model year 1969.
- For 69, the valve was generally used on 12-bolt axle applications, except for JL8 equipped cars (which had disc brakes in the rear and didn't need the valve). As noted above, the 69 NOR Z28's did not use it until mid-year, in the late January / early February timeframe. Other exceptions in 69 include: some SS's and LM1's have been observed without the valve, and the valve has been observed on some drum brake 10-bolt axle cars.
- Note that usage of the valve on 67-69 Camaros was not apparently related to J52 disc brakes.
source: ©1998-2012, Camaro Research Group
Edited by Kurt Sonen and Rich Fields
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