Author Topic: Brake lines - MC to distribution/ prop valve (Read 1214 times)

Jonk67 · « **on:** March, 24, 2010, 11:36:49 PM »

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.

I can get the brake light switch wiring pigtail on as it is right now too.
Thanks, Jon

blue65coupe · « **Reply #1 on:** March, 25, 2010, 05:22:49 AM »

Looks good. If it's fitting properly I wouldn't worry about looping it.

Fast68back · « **Reply #2 on:** March, 25, 2010, 05:26:34 AM »

Nice fab work! Looking good.

sigtauenus · « **Reply #3 on:** March, 26, 2010, 09:35:19 AM »

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.

Midlife · « **Reply #4 on:** March, 26, 2010, 03:31:51 PM »

Quote from: sigtauenus on March, 26, 2010, 09:35:19 AM

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.

Yes. The loops help flexure and prevent fatigue failure of fairly brittle steel lines.

Mach1ne · « **Reply #5 on:** April, 11, 2010, 04:01:40 PM »

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.

Jonk67 · « **Reply #6 on:** April, 12, 2010, 11:11:21 AM »

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

Mach1ne · « **Reply #7 on:** April, 12, 2010, 12:58:56 PM »

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

Jonk67 · « **Reply #8 on:** April, 12, 2010, 08:36:23 PM »

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

daveSanborn · « **Reply #9 on:** April, 15, 2010, 05:26:40 AM »

Quote from: Jonk67 on April, 12, 2010, 08:36:23 PM

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

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.

SELLERSRODSHOP · « **Reply #10 on:** April, 15, 2010, 07:12:44 AM »

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.

daveSanborn · « **Reply #11 on:** April, 15, 2010, 07:29:47 AM »

Quote

drop down bracket

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.

buening · « **Reply #12 on:** April, 15, 2010, 10:42:43 AM »

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.

daveSanborn · « **Reply #13 on:** April, 15, 2010, 12:13:39 PM »

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.

buening · « **Reply #14 on:** April, 15, 2010, 12:31:11 PM »

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

Mach1ne · « **Reply #15 on:** April, 15, 2010, 04:49:52 PM »

Here is what my final product ended up like.

The prop valve is down and to the left of the MC.

Jonk67 · « **Reply #16 on:** April, 15, 2010, 06:42:06 PM »

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

SELLERSRODSHOP · « **Reply #17 on:** April, 15, 2010, 10:24:58 PM »

Quote from: Jonk67 on April, 15, 2010, 06:42:06 PM

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

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.....

Mach1ne · « **Reply #18 on:** April, 16, 2010, 04:15:58 AM »

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.

Jonk67 · « **Reply #19 on:** April, 16, 2010, 05:01:41 AM »

Quote from: Mach1ne on April, 16, 2010, 04:15:58 AM

I can actually twist on my knob without getting out of the drivers seat.

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

Mach1ne · « **Reply #20 on:** April, 16, 2010, 05:54:00 AM »

Yes. I got it from Shaun.

I used a Dremel cut off wheel to cut the knob off the valve without damaging the threads.

Here is the link.

http://www.streetortrack.com/Brake-Bias-Adjuster-pr-21714.html

buening · « **Reply #21 on:** April, 19, 2010, 11:42:46 AM »

Good call on the remote knob. I read about someone installing the adjustable proportioning valve atop the trans tunnel inside the car. He had issues with a soft pedal and finally figured out that his proportioning valve was creating a high point in the system between the front and rear, allowing for air to get trapped at the proportioning valve.

Jonk67 · « **Reply #22 on:** April, 20, 2010, 06:30:51 PM »

Okay, I think I'm finally comfortable with my distribution/prop valve lines to MC now that I have loops in both. The NAPA poly lines bend really easily, I used their kit and scissors type bender to start my bends to 90*, then wrapped the rear most one around a tall 3/4" socket for a tight loop and the forward one went around a 7/8", no kinking, slow and steady wins the race.
Word to the unwise (me) pick your line length you think will fit, lets say a 12" line, then cut a piece of coathanger wire to 12" and bend it in the shape needed to make sure it will reach once all the bends and loops are in it and to give you a template to follow. I wasted 2 lines (~$4ea.) by either coming up short or bending in the wrong 90* direction or starting my loop the wrong direction. Lesson learned.

Thanks for the help along the way, time to tackle the rear line forward and the 3/8" fuel lines so I can return the NAPA line bending/flaring kit and get my $100 deposit back.
Jon