67 68 Camaro manual drum brakes

[JohnZ]

Good post - excellent photos!

[sebastien]

nice work Jeff,thanks for all the good info!

[rich69rs]

Following 7 posts are pages from Delco Drum Brake Service Manual; 17D-11; January 1971; Dealing with Master Cylinder Reconditioning.  Note reference to check valves only being part of the drum brake master cylinder on pp 4-26 (4th post in this series.)

[rich69rs]

Second page

[rich69rs]

Third Page

[rich69rs]

Fourth page

[rich69rs]

Fifth Page

[rich69rs]

Sixth Page

[rich69rs]

Seventh Page

[sebastien]

thank you for sharing Rihard!

[Flowjoe]

So do power drum brakes receive the RPV?  How about the rears on a power disc brake set up?

[Steve68]

Question 1: Yes. Question 2: No.

Steve

[Flowjoe]

Question 1: Yes. Question 2: No.

Steve

That seems odd.  Given JohnZ's explanation of why the RPV is necessary it would seem that the rear drums on a Power front disc car would need them as well, escpecially since a power drum car needs them (which implies that the booster does not do the same job as an RPV).

I'm not saying your wrong, just clarifying the logic.

[Steve68]

I think I misunderstood your second question.  I thought you were indicating the rears were disk brakes.  If the front are disk and the rears are drum then the front outlet (to the disk brakes) does not have a check valve in the outlet and the rear outlet (to the drums) does have a check valve.  The check valves provide a residual 8-10 pounds of pressure on the line to hold the wheel cylinder internal cups against the wheel cylinder wall (to seal it around the cups perimeter).  Sorry if I misunderstood the question to start with and confused you.   

Steve

[bc69]

I just installed a new master with a rear check and after bleed down good the rear brakes would drag bad and hardly release. Thought it to do with RPV so pulled it and they now release fine. The aftermarket I removed didn't have one either.
Any thoughts or ideas?