Rear brakes weird!

[rb68rr]

When I power brake my car to around 1800 rpm's I can feel the back wheels jerking. If I watch them they will jerk forward then stop then jerk forward then stop,etc. What's causing this? Can only hold around 3 lbs of boost at the line before they start spinning. Stock brakes with good shoes. Thanks, R.B.

 

[FreeBoost]

May be the combination valve. Has it been upgraded to the brass valve?

 

[rb68rr]

Not that I know of. What's its purpose? How can I tell?

 

[FreeBoost]

It's a proportioning valve and a metering valve. The proportioning valve cuts the disc pressure (~1600 psi) back for the drums (~600 psi). The metering valve delays the pressure to the back.

Look underneath the car roughly at the firewall on the DS.

Look at Kirban's site, part # 7189 to see what a brass one looks like.

 

[rb68rr]

Mine's brass. Can't figure out why I don't have much pedal. Bled the brakes yesterday and they are still really soft!