[JoePapa]

This is on a '69 Firebird. There's a proportioning valve that has the front brake line come into this 2nd valve. The fluid comes in then out from it to both sides originally. It now goes through a line lock to both sides.

I recently swapped to a hydroboost brake booster that has a disc disc MC as I have 4 wheel disc brakes.

What is this 2nd valve and do I need it?

The car was originally disc / drum.


Thanks!

[Schurkey]

If it's a valve on the FRONT DISC BRAKE hydraulic system, it has to be a hold-off valve. Prevents front disc brake application until the rear drum brakes have enough pressure to overcome the return springs.

If you have discs all around, you shouldn't need the hold-off valve.

[JoePapa]

Thanks. I have factory disc up front and the rear drums were replaced with the Aerospace disc brakes when I went to the Dana. I was thinking it probably may not have been needed but wasn't sure. Thanks for the help, much appreciated!!