Why are some Chevy master cylinders mounted on a slant?

[Tom Boehm]

I went to a local car show yesterday where there were way too many Chevelle SS, Camaro SS, and Corvettes that went on past the horizon. I noticed that some with power brakes had the booster and the master cylinder mounted at an angle. How do you put brake fluid in these? Wouldn't it just run out? I asked two owners about this and one said "I don't know, I've never put brake fluid in it". The other said "I don't know, I just bought this car". This is why I don't go to many local car shows. 

[Frank DuVal]

It has to do with the design of the firewall. Why, well I do not know. While the slant means the level of the fluid is not parallel with the top line of the  master, it still holds enough brake fluid to operate safely. If you look at it, it is tall. And these are usually "quick take up" masters, with the large front reservoir and the small rear reservoir. The large front feeds the front calipers, while the small rear feeds the rear drum brakes.

[Rusty_OToole]

Almost always the answer is, it saved a few pennies on the assembly line. It was more convenient to put it there, they used an off the shelf master cylinder not designed for such use, but it worked so what the hell.

[joe_padavano]

I suspect the main reason is to provide clearance to allow a valve cover to be removed from the engine without having to remove the M/C first. Keep in mind that the master cylinder and booster were typically used across all GM car lines, so the clearance issue might have been with a 455 Olds instead of a 396 Chevy, but it was still an issue. Also keep in mind that at least 3/4 of those cars you've seen likely have an aftermarket disc brake conversion, so whether or not the factory M/C was at the same angle is not known.

[Tom Boehm]

Good thought Joe, I didn't think of the possibility that it was an aftermarket conversion. It seems the master cylinder would not hold as much brake fluid and it would be more likely to leak when it is mounted at an angle. Maybe you are supposed to park going down a steep hill when filling. 

 

To be clear, I think 1969 Chevelles and Camaros are neat cars. My family had one of each when I was growing up. It just seems like the SS cars have a 150% survival rate. 

Edited October 15, 2023 by Tom Boehm (see edit history)

[joe_padavano]

1 hour ago, Tom Boehm said:

Good thought Joe, I didn't think of the possibility that it was an aftermarket conversion. It seems the master cylinder would not hold as much brake fluid and it would be more likely to leak when it is mounted at an angle. Maybe you are supposed to park going down a steep hill when filling.

Also note that under panic braking, the nose of the car dives and the fluid in the M/C surges forward. Mounting the M/C tilted upward mitigates the risk that fluid will leak out the front of the reservoir or uncover the compensating port at the bottom of the reservoir under those conditions.

[Frank DuVal]

8 hours ago, Tom Boehm said:

It seems the master cylinder would not hold as much brake fluid and it would be more likely to leak when it is mounted at an angle. Maybe you are supposed to park going down a steep hill when filling. 

It holds plenty of brake fluid. Enough for a large slug of fluid to feed the front calipers. If it leaks , a seal is bad, since these are sealed master cylinders! They started sealing master cylinders sometime in the early 60s, if not earlier. The sealed masters have the bellows under the lid, as air never touches the fluid. As with any fluid, check with the car level.

[Shootey]

19 hours ago, Tom Boehm said:

To be clear, I think 1969 Chevelles and Camaros are neat cars. My family had one of each when I was growing up. It just seems like the SS cars have a 150% survival rate. 

My fav in the late 1960’s was the Camaro Z-28 especially because Mark Donahue raced it in Transam. It had a de-stroked small block Chevy to come within the 5 liter Transam  limit. Now you see all sorts of 1969 Camaros with Z-28 badges and striping. In most cases the restorer admits it when they are not original, authentic Z-28’s. 

[rocketraider]

2 hours ago, Shootey said:

My fav in the late 1960’s was the Camaro Z-28 especially because Mark Donahue raced it in Transam. It had a de-stroked small block Chevy to come within the 5 liter Transam  limit. Now you see all sorts of 1969 Camaros with Z-28 badges and striping. In most cases the restorer admits it when they are not original, authentic Z-28’s. 

The running joke around here for years has been that there were more Z/28 in Danville VA than Chevrolet ever produced.

 

The Chevy dealer kept Z/28 emblems on the shelf. Didn't make any difference if the Camaro was a six-cylinder Powerglide with bench seat, an RS/SS 396 convertible, or anything in between. If there was a 67-69 Camaro in Danville VA, it was going to be a Z/28.

 

Some of those Camaros are still around here and they claim their own little corner at any show or cruise night in the area.

 

I have a good friend who is VERY knowledgeable about Camaros and is a stickler for correct and authentic cars. I have seen the owners of these bogus Z/28s hurriedly pack up and leave when they see my bud and his brothers headed their way.