Mini booster & MC for drums

[red65FJ40]

I need a little assistance or second opinion i guess. I have a '65 w/ SBC, '72 drum brake axles, and am putting in a 79 Mini Truck booster/MC assembly. booster/MC are alread adapted to my early firewall and now i'm at the point of making connections. I understand I should need to add a 10# residual valve for the front circuit to work properly w/ my drum brakes. The "new" Master Cylinder should have a residual valve already in it at the rear port as the '79 had drum rear brakes.

What I'm finding is there doesn't seem to be a residual valve in the rear port, at least I don't think so. No white plastic disk, just the copper ring. Same as what i'm seeing in the front port. I read Slickrock's thread and considerred pulling the residual valve off my old '65 MC, but it appears to be of a different design, and more integrated into the inside of the MC.

so I believe i'm just in need of two 10# inline residual valves from summit or such, one for the front circuit, and one for the rear. Correct? Anything i'm missing here? I guess I just don't want to double up the rear circuit on accident, not sure if that would even happen, but I would think it might. Anyways I'd appreciate any advice you have. Pics included.

Thanks in advance

Ames

 

[TRoss]

Here's a pic of my '85 Toy truck w/LC 1"MC, dual diaphragm booster, proportion valve and a 2# residual valve for the rear GM discs....

The 1" FZJ80 LC master has residuals built into it, front and rear as they were 4wdb. I was not aware of the mini MC's having residual valves in them for the drum circuit and would have assumed the early drum LC's would not have residual valves either. Hence: adjusting the rear drum brakes. But I've been wrong before... (many times actually ) I added the additional resid valve based on other experiences... sooo... I don't know if it makes any difference or not. I would like to test it without one and then with a 10# just for grins... Currently it stops very well, but I'm still not thrilled with the peddle feel.

Also, I would be interested in how you adapted your booster/mc to the firewall... (workin' on a '70 40)

Hope this helps some.

 

[bsmith123]

nice

I think you might be able to see the pressure at the bleeder if you have a residual valve in the MC already. I am not familiar with that MC though.

Probably if you had 2 inline one would no doubt close before the other so pressure would bleed back until the weaker of the 2 closed. I think that would probably be the effect of 2 residual valves.

10 lbs is pretty common but I think the fj came with 6lb valves if you did use a 10lb valve and already had a 6lb then the 10 would close first and do all the work and the 6 would be redundant





Nice Looking setup you have there TRoss

I like the idea of the adjustable proportional valve so you can dial it in the way you like. the pedal feel might improve if you went to a 6 or 10 lb residual---you get the feeling like you have to pump the brakes?

I just drove my 71 the other day with drums all around and I was pleased with the fact that it stopped straight and didnt pull and the pedal feel was normal but different than modern discs, takes a little getting used to.

You may need to adjust the brakes. The residual will keep the pistons from retracting and keep the pedal high and firm but as the brakes wear they still need adjustment

One last enhancement for the brakes could be a metering valve---this applies the rear brakes just before the front and prevents nose dive. A combination valve is a proport and metering valve put together as one so there are a lot of options depending on the combination of brake parts you are using

 

[red65FJ40]

TRoss thanks for the input, heres some pics of my "homebuilt" adapter. there is the JTO option, but when I picked up my '79 mini booster/MC it came with an aluminum spacer and steel plate. I decided to use the steel plate as the mounting plate for the booster, and welded 4 - 1/8" thick side plates to a 3/16" firewall mounting plate which i drilled to match the 3 hole pattern. Fairly simple, and I figured the money spent on a JTO part could be better used elsewere. Just the approach i took, no doupt thier's probably looks cleaner, but I had the steel at hand and enjoyed the project.

I agree with Bsmith, you've got a clean looking engine compartment there. Sounds like you both agree going w/ the add on residual valves should be a good first step. I don't have a pressure gauge to read the line pressure at the bleeders, probably won't make the investment...

Drum brake circuits should (as i've read on Mud) have a 6-10# residual valve which compensates for the pad return spings on the drum brake general design.

I think what's throwing me the most is i just don't see how the white plastic disc would fit inside either frt/rear cavity of the MC w/ the 10mm adapter fitting, or atleast the ones i've got.

any one else have some experience or advice?

Ames

 

[red65FJ40]

Hey another thought/question, from what i've seen online the wildwood 10# residual valves have 1/8" NPT female fittings, how common is the adapter to go from 10mm male double flare to 1/8" NPT?

thanks

 

[bsmith123]

in line valve

You should be able to make a hard line to plumb it in inline and just put the fittings you need on each end ---metric on one end and npt on the other

 

[TRoss]

Nice Looking setup you have there TRoss

I like the idea of the adjustable proportional valve so you can dial it in the way you like. the pedal feel might improve if you went to a 6 or 10 lb residual---you get the feeling like you have to pump the brakes?

You may need to adjust the brakes.

Thanks.. been workin' on the ol truck for too long. Then my kid drags in a 40... sheesh!

It's the amount of peddle travel (push rod is per fsm). No adjustment as it's disc all around . I may try a 10# next time I have the system open. The prop valve is pretty much adjusted all the way out in order to get the bias desired.

Drum brake circuits should (as i've read on Mud) have a 6-10# residual valve which compensates for the pad return spings on the drum brake general design.

Thanks... more info I didn't know. I remember seeing your pics now.. sorry for the repost. Thanks, it's got me thinking.

Hey another thought/question, from what i've seen online the wildwood 10# residual valves have 1/8" NPT female fittings, how common is the adapter to go from 10mm male double flare to 1/8" NPT?

From resid to hard line there are two fittings.
1ea 1/8" NPT male to #3 JIC female swivel.
1ea #3 JIC male to 10mm female.
That's how I adapted it... I'd rather had a 1/8" NPT male to 10mm female but this is the best I could come up with at the time. I've since scarfed up a few new links that may have said fitting (thanks MUD!).

If your asking if there is an 1/8" NPT to AmStd flare fitting I'm pretty sure I remember seeing it on Summit's site wishing it was metric!!

 

[bsmith123]

discs

Sorry I thought you had drums---most often used is 2lbs for the discs I thought