Hi,
I have a 68 camaro that was originaly a manual drum-drum car. I have just installed front disc from a donor car and was wondering what I should do for a P valve.
Looking through the site I see alot of power brake solutions but nothing that addresses manual disc-drum.

One parts house told me that no P valve was needed, that would be great.

My assembly book shows a valve on the drivers side frame on the rear line. What does this item do?

heres a link to the frame mounted valve.
http://www.rickscamaros.com/cgi-local/SoftCart.exe/cgi-local/smpagegen.exe?U+scstore+tlbk8502ffd379d3+-p+-c+scstore.cfg+DBC-52

Valve or no valve?
Just want to put it all together at one time the right way.


Thanks,
James.

That valve is what is commnly know as a brake hold off valve. It is there to allow more pressure to the the front disc brakes then the rear drum brakes. I am not a expert on this, my answer may seem a little simplistic but that is my general understandng of what it does. The porportioning valve is usally located under the master cylinder booster combo. My 68 with disc/drum does not have a porportioning valve and it works great. But i do think you really need the hold of valve.

You could certainy try it without a proportioning valve - make sure you use the correct disc/drum manual MC. What you are trying to avoid is having the rears lock up before the fronts. A lot of factors go into it - tire compounds, tire sizes, weight distribution, pad/shoe compounds, et etc. I think a safe bet would be to install an adjustable PV in the rear line so you can dial it in exactly.

The metering, or hold off valve (the round one) was to delay application of the front brakes until around 40-50 PSI was built up in the system. I recall reading that before they came out with that valve, people would be sitting at a stoplight on an icy road with light pressure on the brake pedal (auto trans car) and while the fronts were holding fine, the rear wheels would start spinning and the car would creep sideways. It's not really a protortioning valve as such - just to make sure the rears begin to apply before the fronts. For a summer driving only car you could do away with that valve and you'd probably never miss it.

PS I'm not a brake expert, but I AM an expert at regurgitating what I've learned here at the Fabulous TC!

PPS Wow - 3,000 posts. I need a life.

Great info guys.

I am still poking around on the subject and have found a little more.

Per MP brakes site-> What does a metering valve do?
A metering valve or "hold off valve" is used in the disc portion of a disc/drum system to hold off the application of the front discs slightly allowing the slower reacting rears to catch up. This provides rear stability on wet surfaces and reduces excessive pad wear.

More infor here->
http://pozziracing.com/prop_valve_info.htm

Kinda conflicting info but all seems to revolve around wet driving that I never do in my Camaro.


68Holdon, You do not have a pro valve but do have the holdvalve on the frame?

Thanks.

Yes i do have the hold off valve on the frame. I am sorry that my original post had the info on the hold off valve backwards.

Thanks 68Holdon, I think thats the way I am gonna go...