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Brake lines - MC to distribution/ prop valve

Jonk67

Jonk67

Well-Known Member
Mounted up my booster and MC, fabbed a bracket to hold the Summit (SSBC) distribution/prop valve and started running lines. Picked up the polymer lines from NAPA, pretty impressed with them, hard to scratch unless you use pliers on them...rented their bending/flaring kit which is really nice also, benders are like pliers. I think I'll be doing all my brake lines with this polymer stuff.

Give me some pointers on my lines, I picked up prefabbed 8" lines with mixed fittings to fit the forward inlet (rear brakes), do I really have to have a loop in it for that much flex? Should it move enough to need more than the slant it could flex a little? I'm hoping I'm good to go otherwise I'll have to get a 12" one and cut/flare/loop which is ok but I'd rather do it right NOW.

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I can get the brake light switch wiring pigtail on as it is right now too.
Thanks, Jon
 
I never understood the loop deal on MC lines. Is flex the reason? Not sure how much flex is between the MC and the apron.
 
"sigtauenus" said:
I never understood the loop deal on MC lines. Is flex the reason? Not sure how much flex is between the MC and the apron.
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Yes. The loops help flexure and prevent fatigue failure of fairly brittle steel lines.
 
I had fabbed up a set of lines without the loops until I noticed that amount of flex in the front end when having the car up on jack stands.

I now have lines with the loops just to be safe.
 
Mach1ne, you're referring to the lines that go from the prop valve to the wheel hoses, right? I guess there may me more need for give with that distance. Hopefully there won't be much flex between the rear apron and MC.
Jon
 
Jon, I am referring to the lines that run from the master cylinder to the distribution block on the the inside fender wall.

There is a bit of flex there between the fender and the firewall.

Later.

Skip
 
Didn't realize it could flex that much Skip, guess I better get a longer line and put a loop in it to be safe as I plan to push the car at various track outings (1/8, 1/4, opentrack) when I get chances to.
Jon
 
"Jonk67" said:
Didn't realize it could flex that much Skip, guess I better get a longer line and put a loop in it to be safe as I plan to push the car at various track outings (1/8, 1/4, opentrack) when I get chances to.
Jon
Click to expand...

Any "flex" that I've noticed is the result of the master cylinder moving slightly when the brakes are applied. It won't move much, but under hard pedal application it'll rise slightly. I'm not sure if this is the result of a weak firewall or not, but I've noticed it on a few cars where the firewall looked pretty solid.

An alternative to bending "loops" into the lines that run from the master cylinder to the prop valve is to not affix the prop valve to the fender apron. I've done quite a few cars and have always let the prop valve "float". The four lines connected to the valve are more than enough to support the weight of the valve.

Notice in the below in-progress photo where/how I installed the prop valve. The prop valve is connected to nothing but the four lines going in and out of it. It works for me.

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you could also make a drop down bracket that will support the prop valve that attaches to the master cylinder mounting studs. alot of the older chevys used those from the factory.
 
drop down bracket
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Note that in my photo above there's an uninstalled anodized bracket laying on the driver's side frame rail. This was the drop down bracket for the prop valve, but it's use interferred with the structural tubing I welded into the engine compartment.
 
Dave, while it may have worked for you I would be worried about the proportioning valve moving and fatiguing the lines that are attached to it. You have an unsupported mass held in place by skinny lines that flex, which would allow the valve to oscillate due to engine or road vibrations. Not saying it won't work, just a concern I'd consider.
 
I'm with ya and I'm surprised that it took this long for someone to say something.....

The good thing is that the "mass" is small and the four lines holding it are all new (read solid, not old and rotting). Having the prop valve "floating" probably isn't the greatest idea on earth, but I'm betting that it'll outlast me.
 
Agree with you that the mass is light and may not really be an issue. If it's a car with one heckuva idle lope then I'd reconsider regardless of the mass. :lol
 
Thanks for the ideas, I think I'm just going to replace the one line (rear brake) and put a loop in it with a longer line as they are so easy to bend. I have an adjustable knob so I will be twisting on it at some point, plus with it mounted with the bracket I made it keeps it where I can get to the knob.
Jon
 
"Jonk67" said:
Thanks for the ideas, I think I'm just going to replace the one line (rear brake) and put a loop in it with a longer line as they are so easy to bend. I have an adjustable knob so I will be twisting on it at some point, plus with it mounted with the bracket I made it keeps it where I can get to the knob.
Jon
Click to expand...

there's nothing like being able to reach your knob when you want to twist on it :lol :lol

sorry, that door was left wide open.....
 
I can actually twist on my knob without getting out of the drivers seat.

I am using a remote bias adjust gizmo so that I can adjust the prop valve from inside.

These bias adjusters are not really for prop valves but they work perfectly. All you have to do is remove the knob from the prop valve on screw this on in its place.

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"Mach1ne" said:
I can actually twist on my knob without getting out of the drivers seat.
Click to expand...

If I could do that, I'd never leave the car....sorry just following Steve's lead :vic

I may add one of those once the car is all together and I see how often I actually adjust it for different tracks, etc. Is that the one that SorT sells? the pic doesn't enlarge.
Jon
 
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