porportoning valve ratio change

[77leo79]

I have a 77 & 79 Heavy Half Factory stock, one thing I need to figure out is how to put more load to the rear brakes. when loaded on damp or wet roads the front locks up too quickly. All adjusters are in perfect working order,rear drums,pads, new master cylinder,pistons and calipers are excellent. I am a firm believer in using the valve, so is there an adjustment or fix-it or just replace it? I am an ex-18 wheeler so I have a lot of driving experience and am fair to good mechanic with the tools to play with this issue. Any advise on this subject will be appreciated.

[LONGHAIR]

There are adjustable Proportioning Valves that are more designed for race cars but they should do what you looking for.

http://www.jegs.com/cgi-bin/ncommerc...38&prmenbr=361

http://www.jegs.com/cgi-bin/ncommerc...79&prmenbr=361

I'm sure there are others.

[72k5]

I bought one of the lever style valves like in the second link above to solve a similar problem.

http://store.summitracing.com/defaul...ch%2Easp&N=100

When I installed the 14 bolt rear, I had to reduce the size of the wheel cylinders from something like 1 1/4 to 7/8 to balance the brakes. The problem is, I can't really get the benefit from the huge rear brakes when carrying or towing a heavy load.

So, I intend to install the above valve in the rear brake line downstream of the stock proportioning valve, and go back to the large wheel cylinders. You should be able to do the same thing. A Wagner or other brake catalog will list a selection of wheel cylinders that will fit. If you can find a significantly larger bore than you are using now, they should give you the extra braking you're looking for.

BTW, I figure that the lever style is better than the knob style because it allows for repeatable settings, and gives a visual reference as to where it is set. I figured that the knob is more of a trial and error proposition each time you adjust it, and that's something I didn't want in street use.

Unfortunately, I haven't gotten around to the install yet, as running new brake lines into the cab, and doing a clean install is going to be quite a job.

Hope this gives you some ideas.
Mike

[77leo79]

Thanx for the response. I am wanting to be sure about the knob type (is a replacement for what I now have) will give me the ability to totally adjust ratio?? The lever type will have a schedule of settings I guess at or will a set of instructions come with the valve? I don't plan to change the ratios except when towing as I set the trailer brakes to carry the main load. I think I am set up on a 70/30 ratio but have have been unable to find out for certain. Any more help will be appreciated.

[shadetree]

Your issue seems to be the reverse of most guys, IE you have front discs locking up, while most have rears locking up. I suspect your factory proportioning valve may be defective. A dealer, or good brake shop should be able to use gauges to verify braking pressures. If it were me, I would test the system before buying anything.