[smasse64]

...basic question: which reservoir is for rear brakes? I have a CPP universal corvette type dual MC on my 64 Lemans...but holes sizes are generic...only size, so trying to make sure i plumb it correct...thanks...

[smasse64]

drum drum power MC from CPP, a M-C100-L unit

[Old Goat 67]

Both reservoirs same size I believe.
Can be used for either disc/drum or disc/disc applications with or without power assist, according to this.

https://www.summitracing.com/parts/clp-m-c100-l

According to this, it has two different size fittings.

https://www.ebay.com/itm/NEW-CPP-MAS...-/281671412348

If so, bigger line to rear.

I've used a couple of those before, good unit.

Charles

[Tom Vaught]

The reservoir closest to the firewall typically goes to the front brakes.

Tom V.

[smasse64]

...so, as i understand, no problem with size res. front or rear since this MC can handle 4 discs according to CPP site...given that, use the larger fitting to the rear brake line then?..no diff in pressure to rear or front?..these just have a brass dist block for plumbing lines to front and rear....so bigger line goes rear, no resid press?..

[Dick Boneske]

The front brakes are always the dominant ones, regardless of disc or drum. The purpose of the proportioning valve on front disc/rear drum brakes is to maintain the fronts as dominant. I believe the ratio is supposed to be about 60/40, but guys like Tom Vaught know those numbers better than I.

[smasse64]

..they say the front reservoir/port goes to the front brakes and the rear to the rear lines....has nothing to do with capacity of fluid reservoir, as this CPP product is sized to accommodate up to four disc/calipers...so on a drum/drum, no issue...it is the stroke length of the piston that determines where the front reservoir goes.
hope this can help someone else, at least as it pertains to this type of corvette style ClassicPerformanceProducts (CPP) MC's...

[Tom Vaught]

Might want to read this whole article and look at the pictures. https://www.speedwaymotors.com/the-t...d-design/28678

Factory stuff is designed a given way and knock-off stuff can be random in how it is plumbed.

If you want more pressure applied to the front disc brakes for example you use a smaller piston master cylinder (example 1" vs a 1.25" piston). The pedal has to move farther with the smaller piston to supply the volume but the pressure ratio applied to the front brakes will be higher with the smaller piston (good if you have manual brakes).

If you have power brakes either size piston will work: 1" or 1.25" piston Master Cylinder.

I used to try to find the 7/8" Corvette Disc Brake Master Cylinder usits because of the low vacuum with the cam I ran.
Had to run manual brakes.

But today with the Hydra-boost technology, I just don't look any more as the Hydra-boost system can easily activate the master cylinder even with the largest bore pistons in the calipers. Same deal with multi piston calipers.

Hope this helps.

Tom V.

[geeteeohguy]

The rear reservoir (which is sometimes quite a bit larger) goes to the front brakes, which do about 75% of the braking.

[smasse64]

.....front brake lines to front res....June 2018(new dual CPP corvette style MC)..by a classic car mechanic....car stops, but never been happy with it since last yr when this post was orig. made...now, this summer(Sept 2019), I changed up all new rear shoes, new spring kit and new adjuster hardware in both rear drum brakes...for ****s and giggles I jacked car up by the rear end and ran trans in drive at idle, rear wheels off ground and spinning about 15 mph...applied brakes..and no matter how hard i pressed pedal..i got ZERO rear brake...whls continued spinning!!..i used E brake and the rear whls stopped!!!
WTF???...do you think it is my rear line plumbed to the rear reservoir on MC???
I seem to remember getting decent bleed on rears(as mechanic did piss poor job and pedal was awfully spongy when i got it back)...how could i have this..he changed all the rear and front lines to new stainless and did rubber center line over the rear end also...???..help!!!..thanks

[tempest1964]

Have you adjusted your shoes for the drums you have?

[Tom Vaught]

http://www.corvetteamerica.com/catal...nt-brake-lines

As was posted the rear fluid reservoir goes to the front brakes.

The front fluid reservoir goes to the rear brakes.

Tom V.

[smasse64]

...I got a message from CPP that front reservoir goes to front brakes and rear to rear brakes...??..this is opposite what you advised Tom...what gives??..yes, i have the shoes adjusted somewhat close...i can get drums off, but only by wiggling and tugging..they are not too tight, but pretty close without being tight...tough to do by spinning wheels as i have posi rear...but what gives here???..i also noticed my rear stainless pre-bent lines from Ames are small diameter tubing to rear and bigger tubing diameter to front??..is that correct, bc someone here in past advised big diameter to rear...find hard to believe that SS Brakes doesn't know this when they pre-bent these kits...

[smasse64]

...that diagrahm was for disc/drum...mine are drum drum...no prop valve, only brass block(new)....CPP says my MC100-l corvette style is same res front and rear, but i am double checking with another tech rep to see if i get same answer...sm

[Shiny]

I am no expert but recall my 70 drum/drum master cylinder had check valves built in. This was intended to maintain residual pressure in the lines.

If your master doesn't include this you may need one. CPP should be able to tell you.

I had a different issue with my rear drum brakes but at one time added a "standalone" residual pressure valve in the rear line. They are available with different pressure levels.

Note items 23 and 24 behind the flare seats:

[389]

Front for front brakes, rear for rear. If its a disc/drum master it matters..

[george kujanski]

having gone thru this recently, here's what I found:

My '67 GTO was not original so I didn't know if it was correct to start with. I was converting to front disks, adding a combination valve, etc. I did not know if the current install was correct, rear reservoir to rear brakes, etc. The rear line to the rear port on the distribution block was a larger size tube and fitting than the front res to front port so they could not get mixed up, but I didn't know if the previous owner(s) had changed anything.

I checked the assy manual and it sure looked like rear went to rear, etc. Took pix at shows and all of the cars had rear to rear. I plumbed mine the same way but changed the tube sizes/fittings to match the ports on the Inline Tube combination valve. The combo valve was larger than the dist block and mounting position ended up slightly different so I replumbed the MC lines and front lines. The front lines were messed up anyway, hence I had no faith that the existing layout was correct and did the resulting investigation.

On a OE disc system with a larger reservoir, the larger reservoir would go to the disc.

George

[Tom Vaught]

With a Drum/Drum set-up I do not understand why you bought a master cylinder for a corvette which is Disc/Disc.

Why did you not just order a stock Power Brake Master Cylinder for ANY PRODUCTION 1967 to 1972 GTO, Lemans, Tempest?

Tom V.

Why Corvette?

[tempest1964]

So, I'm kinda confused (which isn't hard to do). According to Shiny's post, if you run drum/drum you should have built in residual valves in the M/C. Everyone I've contacted says their drum/drum masters don't have built in residual valves. What am I missing?

[george kujanski]

The OE drum-drum masters I have seen (and disassembled) had the valves in the master body. The aftermarket ones don't have them probably because they can be used for disc and drum. The aftermarket guys do sell the in-line valves separately tho.

george