"Hold off valve" vs "Combination valve"

[Skip Fix]

My 65 GTO project needs some brakes just so it stops in the shop. Factory original drums leak like heck. A cheapy disc conversion is my plan for the front , throw a new set of rear drums on the rear,rear discs down the line but not now. The 67-70 cars used a "hold off valve" on the disc side, whereas 71 up used a combination valve that had that as well as the split for the rear drums.

Any difference in performance? Easier to add a 67-70 valve in line as far as using repop lines than a whole redo for the combination valve and don;t think the 65 frame is drilled for the bracket vs a distribution valve/

[a67]

Typically called a metering valve. Purpose is to hold off the pressure to the front disc brakes until the rear shoes hits the drums. Then both fronts & rears are applied together.

The reason this is done is to prevent early wear-out of the front pads. Around town braking without the metering valve would have the fronts being used 99% of the time.

If it were me, I wouldn't bother with installing a metering valve (BTDT on my '67). Even more so when rear discs are planned.

Bob.

[Skip Fix]

So just a distribution block like 4 wheel drums-just pull the RP valve out of the disc section on the MC?

[MonzaRacer]

If it has drums all around use appropriate master cylinder and instead of a combo valve why not use 2psi check valve on the front brake line after installing front disc, and if you keep drum brakes in back use a 10 psi check inline.
Now I do have a pair of 4wd S10 rear disc backing plates with no sheet metal left on them. Swap them on, and just run 4 why disc , then you would use 2 psi check in eack line.

[MonzaRacer]

If it has drums all around use appropriate master cylinder and instead of a combo valve why not use 2psi check valve on the front brake line after installing front disc, and if you keep drum brakes in back use a 10 psi check inline.
Now I do have a pair of 4wd S10 rear disc backing plates with no sheet metal left on them. Swap them on, and just run 4 why disc , then you would use 2 psi check in eack line.

[MCB Matt]

We do sell the basic front conversion kits as well as prebent hardline kits. I can do lines for the round hold off style or the newer combo. The kit will be less expensive with the newer style valve, and since your car is pre-disc, either one won't look factory. I have bumper to bumper hardline kits, made very vehicle specific and they connect right to the new valve.

Let me know if I can help.
Matt

[Skip Fix]

Matt I guess some of the question is does one work better than the other?

[MCB Matt]

No, they will both net the same result. No reason to add another valve running the "stock 67-69" style system. The new valves work great.

Matt