[tempest1964]

George, thanks for the reply. I did know about the add-on residual valves. Guess I was just hoping there was one with built in valves for a much cleaner look.

[Tom Vaught]

George is spot on with his posts about the valves. Not sure if the stock valves are 2-3 psi but that number sticks in my brain.

Tom V.

[Shiny]

I suspect most people get by without a residual pressure valve but don't know.

I was surprised neither the aftermarket master cylinders nor the combo valves have them, but this suggests they are typically not needed.

As I understand, the "need" is only if the suction builds enough when the pedal is released to allow air to be pulled in past the seals in the brake cylinders or if the shoes pull back away from the drums so much they don't engage. Predicting this for any given combination of parts in the system is probably beyond difficult.

My OPINION is residual pressure is desirable, but I don't pretend to know it's necessary.

My only point bringing it up is "it could happen" if all attempts to correct the issue with the basics (master piston sized correctly, shoes adjusted, air bled, etc.) fail to correct the problem.

[george kujanski]

Tom: I think I read the same value in my research.

I planned on using my stock MC for my disc upgrade but was wondering about the valve causing excessive drag on the disc pistons. Testing afterwards letting the car roll on a slight slope, etc. seems there is is very little drag at all. Bought a spare MC in case I had to remove the valve on the front port, but haven't done it since I would have to redo my brake lines.

I'll leave it as is.

George

[LATECH]

Originally Posted by 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.

Always been this way. Period

[Tom Vaught]

A GOOD Brake Engineering Link

https://www.joesracing.com/master-cylinder-math/

Well worth the read.

Tom V.

[tempest1964]

Sharpen your pencils, there will be a short pop quiz after reading Tom’s link!

[bill ryder]

THANKS for the quick lesson, Tom!!! Guess I pulled the 3000 PSI out of thin air OR somewhere else!!!!!!

The older I become the more my CRS takes hold. But I do know I have used a gage on brakes for TS, just don't remember where, when!!

"Bill"!

[Old Goat 67]

Originally Posted by 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.

Originally Posted by LATECH

Always been this way. Period

NO, it does not.

My 67 GTO with 78 Firebird master.


67 Lamnas 67 Tempest. (Not sure where he got his master)

[Tom Vaught]

You have your picture, I will post mine.

"Master cylinders used with disc/drum combination brake systems will use a large reservoir for the disc brake portion of the system and a small reservoir for the drum brake portion. This is to allow for fluid level changes as the disc pads wear."

You are wearing the disc pads more because the majority of the braking is by the front Disc brakes vs the rear drums.

See photo attached. So where is the large reservoir? DOH, in the Rear Portion of the Master Cylinder.

So far you have not proven anything. I will say though that if you have a bastard application then just use the large reservoir fitting at the point for the front brake tube.

Tom V.

[Old Goat 67]

I definitely agree with that Tom!

[Tom Vaught]

2) Connect the front brake outlet of the master cylinder to the port marked "F I" on the top of the Prop Block. The outlet of the master cylinder for the front brakes will typically be the one for the larger reservoir.

Tom V.

[MarkS57]

This one really had me scratching my head. My front disc conversion has the front part of the reservoir connected to the front brakes. I did the conversion according to the schematic I got with the kit, see attached. The kit master cylinder has equal size reservoirs front & back. Also attached are images of power brake master cylinders for a 69 firebird disc & a 73 firebird disc. This backs up the point that the reservoirs size dictates the application but these 2 have the smaller reservoirs in the rear.

[Tom Vaught]

Did you notice that the brake lines come out on the opposite side of the master cylinder on the picture I posted, LOL! 99% of the Master Cylinders have the brake lines coming out and pointing towards the drivers side fender.

Tom V.

[LATECH]

Old Goat .....What the ?????

wow. Thats a new one. Just when you think you know something, you find out you dont know Nothing

[Old Goat 67]

Just saying, my application is reversed from what you and Tom said.
The big reservoir is always for the front disks, as it has to supply more fluid for them to operate properly.

The front reservoir is for front disks, rear is for rear drums. The other photo is from a member here that helped me when I went to hydro boost. He had the same master as I had.

I have used that Corvette master before on other cars and was informed that it works well for disk/drum and/or drum/drum. Doesn't seem to matter, but I'm no brake engineer. ???

[LATECH]

Rock auto actually shows that exact master for a 68 GTO , amongst a few other ones for drum drum setups.

[smasse64]

so, i got CPP to spec the master cyl...they sent the one that they call the 'corvette style' master..it's just flatter i think than others, plus extra volume..anyways, CPP DID say, rear resevoir to rear line etc...so no problem there...but i had a well known mechanic for classics change out ALL my steel lines(22 y.o.), to SS june 2018...never liked the feel, so i re-bled brakes all four corners...better, but still low and soft...until i went to Gettysburg with it on 8 hr highway drive it was ok...but modern a-holes cutting me off and braking every milisecond caused me to re-look at brakes AFTER that trip...jacked pumpkin...re-did rear shoes with riveted shoes, all new springs and greased pivots and new adjust levers/star adjusters..adjust brakes sbnug and ran in drive with drums off ground both side(limited slip)..hit pedal to floor and rears kept spinning..finally i just re-bled rears(like to get some check valve bleeders..used wife for pump down)..re-tested..and worked perfect....no need for any residual valving, just the old dopey son of owner did a piss poor job bleeding..huge air bubble pockets came out...so, ..oh, i also re-adjusted the pin from power booster into the MCyl...it gave me another 1/4" or so of push..kept pedal off floor...my bad from not measuring accurately two yrs ago on re-build of booster and re-install..now all is Great..just in time for our first SNOW 'event' in Boston, Mass. area this coming friday!!..whoopi...car's working the balls now and.. goes to sleep and i wax my skis...gotta have ways to get thru cold, dark season, besides boozing...and can still do some of that after skiing!!

[Skip Fix]

Sometimes the internal piston volumes are different even with equal reservoirs.

From the Strange catalog on their Mopar style.
"The outlet port nearest the pushrod supplies the most fluid volume and should be plumbed to the calipers requiring the most volume. Typically a drag race only car will have the largest calipers on the rear, while a street driven car will have the largest calipers on the front. Attach lines accordingly. "

I want to think I've seen either Chevelle or Camaro MC in catalogs advertised as having the correct front/rear ratio.