[nashcar]

What determined the application of the hold off valve mounted on the frame under the driver seat in the rear brake line. My car is a one owner 400 4 speed with front discs. My Z28 has it and I've read where the Firebirds also did. I do notice the rear brakes grab first without it on the Firebird. I'm thinking the factory overlooked it on my car.

[mgoblue]

I've only seen the frame mounted valve on Camaro's. I wish others would chime in because this has puzzled me as well.

[nashcar]

I thought I read somewhere the Firebird also had it. Like I said, my rear brakes definitely grab first. So much so, my car has the original front rotors at 106,000 miles. I had them turned when I did the resto and the man said I could turn them again if necessary.

[A Schab]

I have three 69's here and they all have the hold off valve. One is a 400 A/C 4 speed and the other two are 69 T/A's, R/A III auto and R/A IV 4 speed.

[frankyboy455]

my 68 convertible 400 with AC has it. It's a disc brake car, but no power brakes. Early built, september 67.

[maxepr]

I have two drum brake OHC 6's on Sprint one 1bbl, No hold off valves, one Oct 68 Auto 350 disc has the valve, 69 T/A auto july build no valve.

[FunctionalShaker]

My understanding is that they were used on A/C, disc brake combo cars.

[maxepr]

My only car that has one is a disc brake A/C 350 auto.

[nashcar]

I'm baffled as to why my car doesn't have one because of the front discs. Maybe it was just overlooked on the assembly line, it definitely needs it.

[mrgto69]

Originally Posted by nashcar

I'm baffled as to why my car doesn't have one because of the front discs. Maybe it was just overlooked on the assembly line, it definitely needs it.

Do you have original lines on your FB or did someone replace them? If they were replaced, they could have gone with the single line instead... I have an early 69 FB... a Christmas car, with disc brakes and it has this valve.

[nashcar]

My car sat inside for over thirty years by the original owner. There was very little corrosion on the car. I restored it and replaced all the lines with stainless. All the lines I removed were in the same good condition. I'm almost positive the line was original.

[RAJ7395]

Gm Drawing 9794863 69 Firebird installation Drawing - Disk Brakes- Valve 3908326 usage (L30, L76, W66, WS4 w/C60)

L30 = 350
L76 = 350 HO
W66 = 400 Sports Option
WS4 = Trans Am Option
C60 = Air Conditioning

[nashcar]

So must be my 3.36 rear gears makes the difference. Thanks for the info.