Guys, I am getting back in the garage and working on my 71 Comet GT after taking a break. l am having fun!! I have switched my front drum brakes to a disc setup off a 76 Maverick. The spindles went right on. I need to install a proportioning valve but not sure which one to get. AutoKrafters has a brass one that they imply is a factory one, but is not adjustable. Summit has a number of them, some adjust and some do not. Do I need one that adjusts? What is your experience? I will just drive my GT on sunny days and am not looking for a perfect show car, just one that drives well and looks good. Thanks!
with my disc/drum...disc/disc setup I ran the stock drum/drum prop. valve. now that I have bigger tires on the rear than the front...no prop valve at all...the larger tires are my bias...205x60x15...275x60x15...
I have been driving my 71 w/76 front disc brakes for two years now... original drum/drum valve, no issues at all....
Adjustable is the best way to go. On a disc/drum setup, the rears will lock during a "panic stop" with no prop-valve.
This is what my research has found to be the correct valve for the conversion: http://www.mbmbrakeboosters.com/ind...category_id=30&option=com_virtuemart&Itemid=6 You will need to make new brake lines for the front and use the original mount. I got one from eBay for $45 It is on the shelf waiting to be installed. Micah
I've been driving my 73 Grabber for 5 years now with the drum/drum block, with no issues. I put on a set of 75 disc brake spindles, used 74 disc break hoses, and didn't do anything to the lines, everything fit, and works.
You are less likely to need it with disc/disc (especially with bigger tires on the rear) since drums require less pressure to actuate. It's funny how whenever you tell someone the correct way to do something, invariably someone will say "I've always done it that way and never had a problem". Well, it could still happen. I am running disc/drum with the stock drum junction block, and I've never had a problem, but I know I could have a problem, and would be better off with an adjustable prop-valve. I'm not saying you need to run out and get one (you are very familiar with how your brakes react), but it's the best advice I can give to the O.P.
with that being said...where would you take the car to get it adjusted properly... mine, yours and others have worked as is, so are you going to adjust it to work like the stock drum/drum prop valve... I got my info. from a guy that builds...drag cars...(from the ground up)...they have to stop also... nothing is more unpredictable than...Drum/Drum brakes...and they come from the factory with a prop. valve. strange, it works better on...disc/drum brakes... I think the stock prop. valve is more of a...distribution block...than a bias for the fluid...
I don't take my car anywhere to get anything adjusted, except for front-end alignment. I work on my own cars, as do most people who have "project Mavericks/Comets". The stock drum/drum setup, to my knowledge has no prop-valve, and is like you said, a distribution block. You can run whatever you want on your car, and if it works well, that's fine, but when giving advice to people, especially when the subject involves safety, you should always advise them on how it should be done and not necessarily how you are doing it. That's all I was trying to say.
that's why I asked the question...where would he take it to get it adjusted? you suggested he get one, he also needs this info to go with it...
He'd have to adjust it himself. Of course if he doesn't know how to do that, it would have to be explained to him.
Set the proportioning valve midway from full open to full closed as a starting point. Drive the car up to around 35 MPH and apply the brakes hard. This is best done where there is absolutely no other traffic. Large empty parking lots work well. Someone viewing from the side can be helpful. What you are trying to achieve is for the front brakes to be applied just before the rear. If the rear brakes lock up first, the back end of the car will have a tendency to "swap ends" (not a good thing). Adjust the proportioning valve as needed to achieve the above. This may take several trial-and-error attempts. Closing the valve yields full pressure to the rear and opening the valve will reduce the pressure.
:Handshake... only thing I would add is...before buying/installing prop valve...try the stock one and see if you need more/less bias.
