Hi guys so I’m on week 3 of my weekends I’m having no luck at all!! I had to cut my brake line because of my headers, I’ve bought a new booster and proportioning valve now I’m reading I need a hold off valve

do I need a hold off valve?? It’s a 70 cutlass with stock 455, front disk rear drum

Thanks

 

Is this a factory disc brake car or was it converted?

The factory did not use a proportioning valve from the factory. Despite what you may read, the hold-off valve is not a proportioning valve, it is plumbed into the front brakes to "hold off" application of the discs for a fraction of a second until the slop has been taken out of the linkages in the rear drums. On the 1967-70 factory disc brake A-body cars, Olds balanced the front/rear brake bias by changing the diameter of the rear wheel cylinders. Factory disc brake cars used smaller (yes, smaller) rear wheel cylinders to prevent premature rear wheel lockup. The distribution block on the frame was the same as the one used on four wheel drum cars and has no internal valving, again contrary to what you may read.

All aftermarket disc brake conversions use a combo valve similar to what the factory used starting with the 1971 model year. This combo valve COMBINES (thus the name) the functions of the distribution block, hold-off valve, and proportioning valve into a single unit to save assembly cost and reduce potential leak points. If you have a combo valve, you don't want or need an additional metering valve.

 

Should be obvious to anyone reading/following you meant to say "1967-1970" (just a clarification point).

 

But that's what it says... NOW.

Thanks for catching that.