Scottie-GNZ Posted October 27, 2004 Share Posted October 27, 2004 Does the brake m/c resorvoir need to be at the highest point in the braking system? E.g., if something like a line-loc is inserted in the brake lines but ended up being above the resorvoir, would that cause a problem? Seems like since the brake system is not pressurized until you depress the pedal that the fluid in the line-loc could flow back to the m/c possibly causing air pockets. Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted October 28, 2004 Share Posted October 28, 2004 Does the brake m/c resorvoir need to be at the highest point in the braking system? E.g., if something like a line-loc is inserted in the brake lines but ended up being above the resorvoir, would that cause a problem? Seems like since the brake system is not pressurized until you depress the pedal that the fluid in the line-loc could flow back to the m/c possibly causing air pockets. No, the m/c doesn't have to be highest, but you will need a Residual Valve in the line to the back brakes if they are drums, I don't think you need them for rear discs. Not sure on the line-loc, but maybe a Residual Valve in that line would work. http://www.zigsstreetrods.com/zigs.html click on "brake systems" Quote Link to comment Share on other sites More sharing options...
jt1 Posted October 28, 2004 Share Posted October 28, 2004 The reservoir doesn't have to be at the highest point, but the system is much, much more trouble free and requires less maintenance if it is. I used to see circle track guys with the low mounted reservoirs spend tons of time getting air out of their brakes. You can plumb Tilton master cylinders up with a remote reservoir if the MC mounting position is too low. John Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted October 28, 2004 Author Share Posted October 28, 2004 Mike, thanks for the reply. It seems like a residual valve is another term for a proportioning valve. If so I am still not sure if my concern goes away. What I probably ought to do is fully explain what I am trying to do. ****WARNING: I AM GOING TO RAMBLE A LOT OF TECHNO-BABBLE ***** I am installing a line-loc but the line-loc is being installed in the rear brake line, backwards! the RX7 m/c has separate LF and RF lines coming out of it. The LF goes directly to the caliper but the RF along with the rear, goes into a proportioning valve. There is no way I can install the line-loc in the front brakes and have it work for both sides w/o redoing the front brake lines and possibly throwing off the calibration in the p-valve. By installing the line-loc in the rear, backwwards, I get the same effect using a different burnout technique. In this case I have to engage the line-loc, then hold the brakes and the line-loc duing the burnout. This locks the front brakes but prevents any fluid from getting to the rears leaving them free to spin. Unfortunately, finding a spot for the line-loc forced me to put it above the m/c. My concern is that there is no way I can get fluid into and retained in the line-loc when I fill the m/c. So, when I engage the brakes, the fluid from the m/c will be fronted with a pocket of air in the line-loc and this will happen every time no matter how well I bleed since as soon as I come off the brakes, fluid will run (or at least try) back into the m/c. If the m/c is sealed then I will surely make a mess when I open it. Somewhat related to the problem is the fact that I am also installing a hydraulically-actuated throttle stop that extends to limit the travel of the TB while I am foot-braking at the line. The tee for plumbing in this contraption is right after the line-loc so when I engage the line-loc during burnout it does not activate the throttle-stop and limit TB travel. Because the tee connection is also above the m/c, it could affect the t-stop. Still with me? :D Below you see a pic of the installation not 100% done. You see the p-valve is below the m/c and the RF and rear lines come into it from the bottom. The outlet port next to the m/c is the RF and the other port used to go directly to the rears but now goes into the line-loc. Those familiar with the Biondo line-loc can see it is installed backwards. Coming out of the line-loc is a tee with a plug where the t-stop line will go and then the rear brake line. As Richard Pryor would say, "IS THE BOY CRAZY?" :D So, do I still have a concern? Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted October 28, 2004 Share Posted October 28, 2004 Scottie, a residual valve is not another term for a proportioning valve, it's more like a check valve. With a proportioning valve, pressure is reduced going to, lets say the rear brakes. With a residual valve, full pressure goes to the back brakes, but reduces pressure going back to the m/c. That link I gave, the residual valves are the small red, blue cylinders. Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted October 28, 2004 Author Share Posted October 28, 2004 Thanks for the clarification. Sounds like in my case it would best be located in the new line I added between the RX7 p-valve and the line-loc. Quote Link to comment Share on other sites More sharing options...
johnc Posted October 28, 2004 Share Posted October 28, 2004 I am installing a line-loc but the line-loc is being installed in the rear brake line, backwards! the RX7 m/c has separate LF and RF lines coming out of it. The LF goes directly to the caliper but the RF along with the rear, goes into a proportioning valve. My guess is that the RX7 prop valve looks at the pressure differential between the front and rear brakes, that's why the RF brake line is plumbed that way. If you want to simplify the brake plumbing, run the RF directly to the RF caliper and install a Tilton adjustable prop valve back to the rear brakes. Quote Link to comment Share on other sites More sharing options...
A. G. Olphart Posted October 30, 2004 Share Posted October 30, 2004 Scottie, I think a residual check valve would do the job... once you get the system bled initially. They maintain some pressure on the line to the wheel cylinders, and thus no bubble could work it's way up out of the MC. Drum brakes have a relativey high pressure to hold the cups out against the cylinders, and discs sometimes none at all (although there are lower pressure valves available for discs). Come to think of it, why would you even need a valve... the line comes from the cylinder, which should always have only fluid in it. If there are ever any tiny bubbles come wandering through though, they will tend to collect in your new high spot. Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted October 30, 2004 Author Share Posted October 30, 2004 Thanks all. I spoke with Wilwood yesterday trying to understand the applicability of the residual valve and they said it is not needed here. However, I must bleed the highest point and that will not be so easy since there is no bleeder screw at that point. This confirms what another local expert told me. Find out today. Quote Link to comment Share on other sites More sharing options...
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