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Username Post: 1970 GM "Hold Off Valve" for brakes        (Topic#366468)
Posts: 59

Reg: 11-30-08
09-21-21 10:06 AM - Post#2827600    

My 1970 brake system has a "hold off valve" that is inline at the master cylinder that was apparently used on all 1970 GM vehicles with front disc brakes. I am replacing the stock master cylinder with an aftermarket aluminum master cylinder from Summit Racing. Question: should I reinstall the hold off valve or eliminate it? Since the lines are already plumbed for the valve it would be easier to just keep it in the system but I don't know if it's compatible with an aftermarket master cylinder. Any brake gurus out there?


Frequent Contributor
Posts: 2321

Loc: Lake George, NY
Reg: 11-11-15
09-21-21 03:25 PM - Post#2827632    
    In response to 1carguy

Make sure the master you get is specifically designed for disc/drum applications, careful as Summit tends to tell you everything will work. Check the part number at other sites and check the application, if it is right hook it up as the oe was.

Posts: 350

Reg: 07-09-18
09-26-21 12:54 PM - Post#2828017    
    In response to 1carguy

I believe that valve is a pressure distribution valve that limits the pressure to the pressure to the rear wheels to prevent locking up the wheels.

Super Senior Member
Posts: 5898

Loc: paradise
Reg: 09-05-03
09-26-21 02:08 PM - Post#2828034    
    In response to 1carguy

make sure you get the bore size correct. seems that the only way to do that is to measure it.

70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.


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