Thread: Need For Residual Valve?

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Hello,I'm in the process of installing a new mc and power brake booster, on my '31 Chrysler. The m/c is located under the floor,this has Ford Mustang discs brakes up front, Chevy S10 rear drum brakes. Now I understand from reading previous posts that I need a residual valve to keep the fliud from draining back to the m/c. I bought this car and it had been built a few years ago with no residual valve,I'm just upgrading this because the old master starting leaking. Now what I don't understand is, the problems caused when the fluid does drain back into the masterc,without a residual valve?
Thanks,and any help would be greatly appreciated,Brian

It's good to have one in the system whenever the master cylinder is located below the level of the wheel cylinders/calipers. Improves the brake response.

A 2 lb residual valve is used when you are using disc brakes on the front and drums on the rear. You use a 10 lb valve for drums all way round.

2 lbs keeps the shoes in close proximity to the drum surface for a good pedal. Otherwise, the shoes back off and it takes a lot of pedal to get rear brakes every time you stop.

Thanks Folks! I was hoping someone would say it would work fine without them (haha,wishfull thinking on my part!),but will order a set,now that it's clearer to understand how thay work. I am using a Corvette style m/c, and didn't know until today that that lines won't fit without adapters either,so might as well get all the parts sent in at the same time.
Thanks again,Brian

Caution....Corvettes NEVER had disk fronts and drum rears....you say your master cylinder is "Corvette style".....is it a disk/drum master cylinder?

mike in tucson

Originally Posted by robot

Caution....Corvettes NEVER had disk fronts and drum rears....you say your master cylinder is "Corvette style".....is it a disk/drum master cylinder?

mike in tucson

some of those M/C had built in check valves,, are you using a disc / drum proportioning valve?

Hello, This m/c came with an "under the floor" power brake kit,it said Corvette style,I thought it was refering to the ports on both sides. I did order the unit for discs front, drums rear. I checked it for the builtin residual valves, (saw on an older form somewhere on here),by inserting a toothpick and if it stops about a 1/4" in ,it has them, but it didn't.....so I'm assuming it doesn't.
Thanks,Brian

Originally Posted by techinspector1

2 lbs keeps the shoes in close proximity to the drum surface for a good pedal. Otherwise, the shoes back off and it takes a lot of pedal to get rear brakes every time you stop.

Don't you mean 10 pounds for drums, 2 for discs???

If you have drums all the way around and a drum brake master cylinder(single or double), you do not need separate residual pressure valves as they are usually in an all drum master cylinder. Where you have a disc drum master, you will need them

Originally Posted by Oldmanb

Hello, This m/c came with an "under the floor" power brake kit,it said Corvette style,I thought it was refering to the ports on both sides. I did order the unit for discs front, drums rear. I checked it for the builtin residual valves, (saw on an older form somewhere on here),by inserting a toothpick and if it stops about a 1/4" in ,it has them, but it didn't.....so I'm assuming it doesn't.
Thanks,Brian

Thats the correct way to check for the internal valves,, but you still need to use a combination Disc /drum valve [#VL 3350] in conjunction with the check valves
Check out this site,, pretty much tells you what you need to do

http://www.mpbrakes.com/technical-su...igurations.cfm

Originally Posted by paul274854

Don't you mean 10 pounds for drums, 2 for discs???

Yes, thank you. Got caught up in the 2 lb part of it....

Thanks for all the info! I have 2 resdiual valves on order,having difficulty finding line adapters for the m/c,(can't find my thread pitch gauge,have to pick-up a new one tomorrow). I have 9/16"-20 IF,but,not the same thread as the plug,the other is a 1/2"
This kit is an MBM kit, using their # 13214 M/C,checking their site, but no specs. on the site.
Thanks again,Brian

One of thoses days, plugs were in the box,lines fit fine,just me being stupid.

Well, installed the a 2lb. & 10lb residual valves today, and after a lot of bleeding,have the best brakes this old car has ever had,works like a charm. I have to say MBM makes to great setup.,I'll either have to shorten the pedal, or get my legs shortened,but all in all very pleased with it. Nice to get it back on the road,been off since Nov.
Many thanks to all for the info!Brian