The Stovebolt Site Forums The Parking Lot Big Bolts Residual pressure valves

Anyone use them in their trucks?. They seem like a great idea especially for non/daily driver use. Summit has 2 lb for disc and 10 lb for drum for around $20.

Hy alltruck72, the reasons for installing resisdual pressure valves all involve modifying your original brake system in some way. What type, size, and year of truck are you inquiring about?

My truck is a 1942 1.5 ton. I did the brake system this past spring. The truck is not road ready yet, and this valve claims to put pressure on the master to reduce pedel softness? because master is lower than the wheel cylinders. When I don't use the truck I have to pump them up a few times to build pressure, Just wondering if these devices will eliminate this.

If the Master cylinder is lower than the wheel cylinders then it would seem that the line fluid is returning to the master cylinder and what you experience is having to build it back up to make things operate. I am not familir with the residual valve you mention but it seems to me that a pilot operated check valve is in order to keep the brake fluid in the system and has little to do with actual pressure. Is that what it is?

Hi there. I used them on my '46 Chevy 2-ton. I upgraded to a dual-line master cylinder for a 1967 Chevy 1-ton with 4-wheel drums connected to a 7" dual-diaphragm booster run by a "universal" street-rod frame-mounted brake pedal but kept the stock 2-ton drums.

The residual valves were needed as even the "modern" 1-ton master didn't move enough brake fluid to expand the big wheel cylinders to stop the truck and the shoe return springs would push all the fluid out of the wheel cylinders and back to the master faster than I could pump the pedal.

The 10-lb valves hold enough pressure in the lines to keep the return springs from pushing all the fluid from the wheel cylinders without dragging the brakes.

Now, instead of the pedal going right to the floor without the truck slowing down (like it did without the residual valves), the pedal firms up after about an inch and a half of travel and will slide the tires in gravel with just half a pedal's worth of travel.

Pic below.


Brake booster, MC and pedal.

Thanks, Thats what I wanted to hear. Sounds like you are happy with them.

That sounds like what I need for my '70 C50. It has the firewall mounted M.C. and frame mounted booster, brakes take quite a bit of pumping if its sat for a few hours and fluid overflows from the M.C. when you take the cap off. Should the residual pres. valve be installed before or after the booster?

I think that your 70 C50 has something else wrong. Does the pedal return when you take your foot off the brake? Does the push rod that goes into the master cylinder have clearance when the pedal is released?
The residual valves are placed after the booster, I don't think they are needed on your truck.

Pedal returns quickly and smoothly, has about 1/2" freeplay.

On a truck with hydro boost they should be installed after the booster as close to the booster as possible.
On non power or where the booster is between the pedal and master cylinder it should be as close to the master as possible.

My trucks sit for months without moving and I never have a pedal issue. Sounds to me like the MC needs to be rebuilt.

Putting a 1/2 ton MC on a 2 ton truck may work, but you rick not having enough pedal travel to stop the truck. The small diameter MC can't push enough fluid into all of the wheel cylinders, that's why GM made larger MC's for big trucks. Why not find a larger diameter modern MC so you have lots of pedal travel?

Mike B

I have a '54 2 ton,and have been thinking of doing the same basic thing,but I'd like to find a bigger M/C (from a 2 ton) so it'll work as it should.
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