I "need" a proportioning valve for dual m/c with drum brakes WTF??

look for a full sized GM car, 1968 or newer with dual MC and 4 wheel drum and order new parts or hit JY for used, hit JY for mounting brackets anyway.

 

I stand corrected!

 

Shop around a little,Ecklers is one high priced store,you'll find the parts you need elsewhere much cheaper

 

If the car originally used a single master cylinder (1 line split to all 4 wheels), the proportioning was done by wheel cylinder size. A prop valve can't hurt in that situation, but should not be necessary IF all the original wheel cylinder sizes are used.

The main reason for the prop valve is to prevent rear wheel lockup under moderate braking, due to forward weight transfer and self-energizing effect of the drum brakes on a disc/drum setup.

 

English cars of the 60's did not use proportioning valves when using disc/drum combo. Nor did they need one. It's a simple matter of properly designing and sizing components. US manufacturers found it cheaper to dial in a system with a proportioning valve.

A proportioning valve is needed only if the rear wheels lock up when stopping hard. The brake type does not matter. So it is very easy to see if you need a proportioning valve. Have an observer watch the wheels as you slam on the brakes. If the rear wheels lock, you need a valve. If they don't, you don't need one.

Bill

 

This high tech device does indeed prevent "sucky" brakes.

Probably not too new. Did a 37 Packard last year that had em...in the OEM wheel cylinders.

I fully understand the difference in their ratings and use. No springs to worry about in calipers. I'll leave it this way I guess...if you want to run em it may not hurt. I won't and I don't because an OEM system doesn't need them.

 

Either I'm lucky or don't know any better. I've done very similar swaps in '60's Chevys and Fords, drum to drum. All I ever used was something out of a '67-70 similar junk car.

I'd get everything I need in one shot, master, any pedal attachments, lines, distribution block, brackets, etc and swap them into the older car. I always did replace the master regardless.

I never farted around with residual valves, proportional valves, nothing. The cars always bled out and stopped just fine. I'm thinking things have gotten over complicated through the years.

I'd hope that the aftermarket brake community knows what the 're doing. My guess with the proportioning valve is to allow them to stock less parts for a "one size fits most" application. I'd still contact ECI to get their 2-cents.

Bob

 

You'd like to think so... I'd check everything anyway...

 

how about a disc/disc (power)setup seems my rear needs more pressure,(adjustable proportioning vavle), pinch down the pressure up front????????

 

No. Your fronts do most of the hard (save your life) braking. Don't restrict the flow to the fronts in any way.

You may not have large enough caliper pistons at the rear.

 

got it thanks ex

 

Drum brake residual check valves were most/always located internally in car/lt.truck master cylinders until the mid '70s, when they disappeared.

Drum brake cars/lt.trucks never used proportioning valves, but front disc braked vehicles do require them because of the higher pressures disc operate at, (vs. drum) to prevent or limit rear wheel slide. As US vehicle brake regulations became more stringent in the mid '70s, ALL vehicles, both air and hydraulic, eventually required some type of rear axle (brake) slide control.

It's not about stocking less parts, it's making sure all the vehicles, with all their wheel bases/engine options/body types/GVW loads/tire type-sizes, pass the FMVSS 105/135/121 regs.

You would be surprised the lack of information, or mis-information, some suppliers of brake components have of the products they sell, along with some magazine articles, so you really want to do research on your own first, before you completely rely on someone else when working with brake systems.

I know I have an advantage by working with brake systems for many years, but it's still surprising the lack of basic brake system and componet knowledge today, considering how long they have been around! Most older shop manuals go into great detail, even with many pictures, but it seems it's easier to post a question on some web site vs. tryng to learn, you know, like "back in the day", one of my favorites!

 

Thanks for all the inputs. When I get my new M/C I will confirm it has RPV's built in to it. If not, I will add 10 lb external ones. I will NOT be using a proportioning valve since it is a drum/drum setup. Todd