Master Cylinder with plastic reservoir and 15/16 bore?

[ULTM8Z]

any factory cars come with this?

I'm going to be putting on an adjustable prop valve and figured I'd just put on a new MC while I'm at it (considering mine is about 18 years old now).

I have the generic cast iron one now, but wanted to change out to a more modern looking one.

car is a 1971 Camaro with power brakes and Baer 4 wheel disc (MC came with the kit when I did the conversion 18 years ago).

[dontlifttoshift]

I went through this and ended up with a Wilwood. Prod #: 260-14242-BK

I just couldn't find an OEM one in the time frame I allowed myself to search for one.

[ULTM8Z]

thanks. though that's quite a bit more than I was hoping to spend.

there are some mid 80s MCs that are 24mm (equivalent to 15/16). I would think that they would have the same bolt pattern to the booster??

[andrewb70]

What about this?

https://www.rockauto.com/en/moreinfo...056204&jsn=613

It's a "quick take up" kind...might work really well!

If you have power brakes, why not the S10 1"? This guy:
https://www.amazon.com/gp/product/B0...KIKX0DER&psc=1

Andrew

[ULTM8Z]

what does a quick take up do for you?

I do need the 15/16 or 24 mm since thats what Baer used in the kit. I've tried 1" before and it was way too hard of a pedal.

[andrewb70]

Donny can probably answer this better, but as I understand it, there are two bores, the larger bore moves a lot of fluid quickly, then the smaller bore takes over and generates more pressure.

Andrew

[badazz81z28]

The quick take up MC is a economy tactic. Old school brake systems dragged the pads on the brake rotors. When you hit the brakes you got immediate braking. The way I understood it was newer systems relax more and create an air gap between the pad and the rotor. The quick take up MC allows the system to allow the airgap, but get quick braking. Overall improvement of fuel economy by not driving with the constant friction. True? I don’t know, but read about it years ago.

[dontlifttoshift]

Yep, quick take up master is for low drag calipers. Low drag calipers have a seal design that retracts the piston further than normal seal designs. Consequently you need to move a lot of volume or have a long pedal, so they went with a stepped bore master.

I didn't realize this was for power, I saw 15/16" and assumed manual. There should be several to choose from then.

[ULTM8Z]

would a mid 80s Camaro MC bolt up?

the ones for disc/drum use 24mm bore evidently. the fittings ar metric, but I'd be bending up new lines anyway.

[CarlC]

Way too hard of a pedal with 1"? If so, 15/16" will only yield about a 12% area difference.

[79 Camaro]

I'm not sure of the bore size but the 2002 Fbdy has a plastic resivoir. Same with the C5 Corvettes. Cheap on the used market.

[ULTM8Z]

I think at this point I'm just going to get the same MC that came with the Baer kit. figure I'll minimize the number of variables here.

[andrewb70]

I think at this point I'm just going to get the same MC that came with the Baer kit. figure I'll minimize the number of variables here.

I'd give that quick take up one a try. It's cheap...and looks good...

Andrew

[ULTM8Z]

any drawbacks to a quick take up without using low drag calipers?

[andrewb70]

any drawbacks to a quick take up without using low drag calipers?

I don't think so. When I first built my GTO I used it in a manual set-up. The only reason I swapped it out was because it didn't have a deep hole in the back of the piston and I was paranoid about the rod popping out. Otherwise it worked well.

Andrew

[a67]

would a mid 80s Camaro MC bolt up?

the ones for disc/drum use 24mm bore evidently. the fittings ar metric, but I'd be bending up new lines anyway.

The line ports are on the right side of the M/C (toward engine). And are metric bubble flare, so be sure that you can do that type of flare and there is room on that side of the M/C. The earlier 3rd gen M/C are inverted flare, but still a quick take up design.

With regular calipers (non-low drag) I don't care for using a quick take up M/C. They are not as easy to bleed and have more moving parts that could fail. Then for some reason GM moved away from using low drag calipers and quick take up M/C's.

Note that the mentioned 2002 f-body ('98 - '02) is a 1" bore with right side metric bubble flare ports. Although it is a straight bore, non-quick take up.

Bob.

[ULTM8Z]

Well I ordered the Baer master cylinder and an adjustable proportioning valve.

This morning I re-adjusted the parking brake cable. Didn't really seem to make much difference in brake performance. The parking brake was never able to hold the car while idling in gear and it still can't. Though I always attributed that to the higher idle speed necessary for the Miniram intake and the very tight stock converter.

Any rate, I guess I'll see if the ~20 year old master cylinder I currently have is really the problem.

[ULTM8Z]

One thing I do notice is that the first ~3/4" of brake pedal travel, there's some resistance (but very little). You don't really feel the hydraulic pressure until after that first ~3/4". I know it's not an issue with pushrod length becuase if I let go of the pedal, it'll return to the original position (and this is without the brake pedal return spring). So during this first ~3/4" of pedal travel, the pushrod is definitely in contact with the MC piston. This is also after releasing all the vacuum in the booster as well.

The funny thing is, the car stops well overall. I'd probably not have made an issue if I didn't discover the issue I described in the initial post, I'd probably just be driving it the way it is. So I want to get that resolved..

[a67]

One thing I do notice is that the first ~3/4" of brake pedal travel, there's some resistance (but very little). You don't really feel the hydraulic pressure until after that first ~3/4".

Check the length of the push rod between the booster and M/C. They being too short is a common issue.

Bob.

[ULTM8Z]

Understood. But if I had a short pushrod, it seems to me that I would expect to see zero resistance on the pedal during that 3/4" of travel. And since without the pedal return spring installed, there would be no mechanism to force the pedal back to the neutral position when I let go. As it stands, there is some minimal amount of noticeable resistance and the pedal does return to neutral each time.

I also did measure and double check the pushrod length when I put it in, so it seems unlikely to me that the I have excessive clearance in there at this point.

Though, I can certainly check it again during the MC and prop valve swap. Won't know until after 1/9 since the MC was on back order at Summit.