IROCZman15

iTrader: (25)

So let me put a disclaimer that the setup on the car currently is only for one single year of use. I will be doing an engine upgrade in December 2019 and during that time, I will be totally eliminating the OEM combination valve/prop valve assembly all together. I will be running all new brake lines and cleaning up that whole area under the master cylinder, but not until the end of 2019. .

Many years ago I did the Drum-to-disc (C4 corvette with PBR calipers and 12" rotors) conversion and bought everything off www.flynbye.com. I have done business with Ed before, and he always comes through. My current rear disc setup is a few days away from being mounted on a brand new 12 bolt axle housing built by Moser Engineering. Over the years, I have always hoped for more bite from my C4 rear disc brake conversion and had read about the common spring upgrade. I had bought a 1LE style prop valve from Ed years ago too, and that is installed on the car, but still not giving me the aggressive rear brake performance that I want. I also learned about plumbing in a in-line adjustable proportioning valve. I read the TGO tech sticky (https://www.thirdgen.org/propvalve/) So, Since I enjoy doing autocross, aggressive street driving, and drag racing.. I decided an adjustable prop-valve was a better in the long run, so I bought the Wilwood 26010922 last week. https://www.summitracing.com/parts/wil-260-10922?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-wilwood-disc-brakes&gclid=CjwKCAiA45njBRBwEiwASnZT515nbtXkghxGo_mZdpIxNrxos0fyaLEjh9eimC9cUkV8nANhwGwLEhoCXNYQAvD_BwE

I fabbed up a bracket from aluminum, cut my existing (1/4" steel) brake line under the drivers side rear seat, flared it,and used some reducers to plumb it to the wilwood 26010922 valve. This valve allows adjustment between 57%-100% line pressure. I am currently unable to fill/bleed the brake system, because until I get the 12 bolt rear axle from Moser (monday) and the brakes installed, the system is dry.


My question here is...... I am Currently (for one more year) trying to keep the OEM style prop valve in its place, so I don't have to tangle with all the brake lines until next winter when the engine is out.
But,Do I :
A. Keep the current spring (a 1LE conversion spring from Ed Miller) inside the GM prop valve and use the Wilwood in-line valve to further adjust the brake pressure?
- Wouldn't I then get LESS pressure to the rears than before ? since the GM spring is reducing pressure and the wilwood's lowest setting only allows a minimum setting of 57% pressure reduction ? But, If I set the Wilwood valve to 100% brake pressure, I would simply get the actual pressure from the GM valve, and be in the exact same position I was before.. which is fine, because the Wilwood valve can be already mounted and setup for next year when the Gm valve is eliminated
- . Or i could remove the wilwood valve and put in a simple brake line union to join the cut/flared lines... then only when I get rid of the Gm prop valve next winter, I'll just take out the union fitting and put the valve back in? the bracket and everything will already be there.. just swap out the union/fitting for the wilwood valve?

B. Remove the spring (and internal plunger) from the GM prop-valve and have it remain as an open fluid cavity, thereby running 100% full pressure down the rear line until it gets to the Wilwood valve where it is then reduced /adjusted?
- however, would this cause an issue with the bais of the existing GM prop valve and the brake light warning switch/alarm?
- how would the pressure not blow off the little rubber cap that is on the outward end of all of our GM prop valves? also, how does that not blow off normally... I mean I know the spring and valve inside kinda block fluid passing to it, but with 1000psi of line pressure inside a sealed brake system,that little O ring really prevents fluid leaking past it and blowing off the little rubber cap??!? if so, impressive!!
- if I leave it as an open cavity, I would have to find some type of nut or brass pipe plug to replace the OEM nut that has the hole in it where the rubber cap is. I searched online for a proper term and the closest thing I found was "proportioning nut" on a few diagrams. Am I searching wring or is this type of thing not at all common? My neighbor brought over a few brass pipe plugs, nothing fit with the diameter/thread size so we think the threads might be metric?

I called Wilwood this morning and they could only technically recommend that I totally eliminate the existing GM prop-valve. I told them I fully intend to do so in December 2019. He said he couldn't advise of anything different than that.

Just looking for the best way to use my current setup, and I am not sure if I should leave the current sping and plunger in there along with the in-line adjustment wilwood valve... or try to figure out how to remove the spring and GM plunger and only use the Wilwood valve for rear line pressure adjustments A

Any help or advice is very helpful. Thanks

QwkTrip

iTrader: (22)

The rear brakes definitely won't work right with both prop valves active.

I'm not fully educated how the OE combo valve works, but I think the return spring pushes the plunger into the "100% rear line pressure" position, so if you remove the spring then the plunger will be pushed back and decrease line pressure to the rear brakes. So I'm not sure removing the spring is a possibility.

I don't know if you have any choice but to remove the OE prop valve. But the key words are "I don't know"

battmann

iTrader: (9)

QwkTrip

iTrader: (22)

IROCZman, is that plunger in the picture from a disc-disc combo valve, or a disc-drum combo valve? Knowing would help me out with something I'm looking into. Thanks.

IROCZman15

iTrader: (25)

thanks for the replies fellas! I totally agree with you both, that as the system sits currently just wont work properly.
I certainly wasn't tying to cobble together something that could be dangerous,. my plan made sense at the time, except I failed to realize that there was that little hole in the front nut, under the rubber cap.
I had basically thought it was a good Idea to get a cross-off project completed while I am working under the car and waiting for the rear to arrive. I have wayy too much damn $ into the car to have a self-inflicted brake system failure and wreck the car.. so there is no way that it was hitting the road without this being sorted out properly. thats why I came here to ask for help.

For several years now, I wanted more from the rear brakes. they have NEVER locked up the rear wheels, even after installing the entire 1LE prop valve from Ed Miller flynbye. At the last autocross I did in October 2018, an instructor sat passenger with me and asked me directly if I had made the rear brakes softer for any reason. I guess he felt the car was braking way too "nose-y", probably something I had simply gotten used to. I did a short explanation to him and he strongly recommended an adjustable prop valve. At That same event, a guy with a 3rd gen firebird had his hood open and I saw he had one plumbed in. he had removed the oem Prop valve completely and used a T block for the fronts, and only the in-line Wilwood valve (that I have) for the rears. He also recommended me ditching the OEM style prop valve, but then said I could also do what I am doing, and have it present and plumed in place... but with no guts in it. I guess he forgot about the little hole in the front nut under the rubber mushroom cap, just like I did too. .. oops

I looked through my parts shelves today and pulled out my old disc/drum prop valve that was on the car from 1987-2010 when it was removed and replaced with the 1LE valve from Ed. I spoke with a few people and I think the best course of action is to either have that one modified (closed up)... or maybe even to simply take the end nut off, have it welded shut.. and then use IT as a sealed off plug on my current prop valve once I remove the spring and plunger completely. someone mentioned to me that if I couldn't find someone locally that can weld the hole in the aluminum nut closed (its aluminum I think? not brass??) I could get a fine thread pipe plug instead. I would drill the hole larger, run a threaded tap through it, and install the pipe plug with some metal sealant for assurance.. Seeems ok, but I will definitely look for someone who I can pay a few bucks to to weld that little hole closed. can't be too hard, I just have no experience welding aluminum and don't want to screw up. unless its brass..it would need to be brazed?

sound like a plan to you guys?

then since there is no spring or plunger inside the current 1le on-car prop-valve, it would simply be a open cavity filled with brake fluid and 100% line pressure would travel through it.. then it would be adjusted/reduced by my wilwood valve under the car ?? sounds right to me, but you guys are smarter. thoughts? would this interfere with the brake pressure warning switch? if so, I will just eliminate that, because to be honest, I think I would simply feel/know if I ever have a brake fluid system leak by the pedal feel and a line of brake fluid on the ground. .Don't get me wrong, i am an idiot, but I don't need an "idiot light" to tell me so.

what do you guys think. weld that little hole shut on the aluminum end nut and it should be good right?

QuickTrip . the one in the photo is the one that I pulled out yesterday from the 1LE valve that Ed Miller sells. I plan on opening up my old drum/disc prop valve tomorrow or monday, and I can take photos of that too for you. I'll put them up here if that helps you.

QwkTrip

iTrader: (22)

Thanks!

Regarding your questions, the pressure switch is on the feed side (high pressure side) so it will work properly no matter the pressure in the rear brake line (that is as long as you don't lose line pressure). The housing is made of billet aluminum. There will be a lot of force on the plug, on the order of 1000 psi multiplied by the surface area of the end cap.

I have a Wilwood 5-port valve with a 4th gen master cylinder and I have to crank up the valve close to max to get the PBR LT1 rear brakes to perform. Naturally I'm going to need a lot of brake on the back because my rear tires are drag radials with substantially more grip than the front, but it did surprise me how far I had to crank on that valve.

As the brake bias improves it also changes the feel of the brake pedal.... And that just doesn't seem right to me. That has made me wonder if the real problem is not enough fluid volume to move the rear brake pistons.

IROCZman15

iTrader: (25)

yea, I wonder if your pedal feel and brake bias feel are common? Also, do you have a 3/16" line now running to the rear brake T-fitting, or did you keep the 1/4" line that drum rears came from the factory with? Wilwood told me that I should definitely go with a 3/16" line to the rear, so that is also on the to-do list for next winter.

I pulled out my old oem original prop valve from the parts shelf and had a look at it. same overall design, but different sized prop-nut. my oem nut took a 3/4" socket. the 1le flynbye one took a 13/16" socket. this made sense when I examined the two plungers inside and their diameter was slightly different. . however, that is not important to me... what was important is that both of them each fit into the other prop valve and screwed in, threads meshing perfectly ! so now I have two front nuts. I will go to a welding shop nearby that I know and see if they can weld shut the tiny hole on the nose of one nut, (or maybe of both nuts) and simply turn the nut into a pipe plug. It will still use the o ring to seal, and maybe i'll neatly put rtv or pipe-dope on it.

the general consensus is that this should work to solve the problem I expressed in post#1. I am thinking that both nuts are aluminum, but the 1le nut (bigger exterior) has a more yellow color to it, so i am wondering if it is brass and maybe needs to be brazed? either way, welded or brazed.. I am banking that this will hold the 1000psi of fluid pressure that will be in the pv cavity. thoughts??


I was advised by a mega TGO member on a PM that I should pull out the top plastic insert for the brake warning light switch and either weld it shut, or put a pipe plug in its place. I plan on doing so. will look for a proper pipe plug tomorrow

Lastly.. the metering valve portion. Why would I want to weld this hole up? I would think that I would want to keep it doing its job of allowing the rear brakes to start grabbing before the front brakes begin to engage. should I leave the nut (with its hole for the metering valve plunger) alone? I know next winter this won't exist on the car anymore, so I guess I can see both answers being correct? thoughts? leave it alone or weld the hole up ?

QwkTrip

iTrader: (22)

This is a long video but it's very much worth watching the entire thing.

IROCZman15

iTrader: (25)

yup, i've watched Klowny's video about 4 times recently. I even left a comment/question for him in the youtube comments section last month using my name "Dave Martin"., Basically inquiring about the situation I find myself in at this very moment!! good stuff. I even emailed him and sent him a Pm here on TGO, but I see he hasn't signed onto TGO in almost 2 years. I am hoping he has a response for me. but as always, any of your guys's thoughts and opinions are welcome and appreciated.

malibudave

The rear PBR calipers have a fairly small piston at 40mm in diameter. That is about 1.58" in diamter. Compare this with an earlier thirdgen cast iron version at 48mm (around 1.875") and a LS1 F-body rear (45mm or 1.77"). That is about 30% and 20% more piston area respectively than the PBR caliper.

Bottom line is, caliper piston size matters.

Add to the lower clamping forces on the rear (about 1/2 compared to the stock thirdgen front setup), you MAY have a wider, stickier tire on the rear which will reduce the tendencies of the tire to lock up, plus you have a prop valve that doesn't work like it should even with stock sized tires on all four corners.

Since you have a non stock front rear tire setup, you could just go with no stock prop valve and just have the adjustable valve for the rear brakes. Start with the adjustment on the rear brakes fully open and adjust it closed to reduce the amount of fluid going to the rear calipers to dial in your rear brakes.

QwkTrip

iTrader: (22)

I've been digging deep on this the last few days. Prop valve will function without the spring but you'll have weak braking. Removing the spring will essentially eliminate the knee of the prop valve curve and it will go into proportioning mode immediately.

IROCZman15

iTrader: (25)

gotcha, yea from reading your other thread, the spring/plunger controls "when" the prop valve functions... i.e. when it activates. cool. good to know

Yesterday, I got the hole in front nut (prop valve) and also the hole in the back nut (metering valve) welded up nicely.
Lastly I think I have to find a pipe plug to close up the hole in the top where the plastic insert goes that houses the brake light warning switch thing. or do I ? it is NOT a normal pipe plug thread/taper. none of the local hardware supply stores or plumbing supply stores can find me a plug that directly fit it properly. ...... question. no fluid is actually IN that passageway/chamber where the warning light switch and the metal contact pin are housed right??? if no fluid is in there, why would I need to seal this off? cant I just leave it as is with the plastic insert, and cut the wire so my brake warning light is not always illuminated on the dashboard? or am I missing something here?

QwkTrip

iTrader: (22)

I don't think there is fluid under the brake light switch. But you wouldn't want to give a chance for corrosion to form inside there either. It's harmless to just leave the switch in place whether you wire to it or not.

QwkTrip

iTrader: (22)

Just FYI....

Now that I know more how the valve works I think you could have simply removed the gasket from the piston and that would have been that.

IROCZman15

iTrader: (25)

you might be right actually. since the gasket retains the fluid flow that the plunger and spring move with (controls the "knee point")it would probably just let fluid flow around the area "freely".

still waiting on a driveshaft to road test everything, but I installed the welded closed plugs on each end, and cut/ tapered a 1/4x20 bolt to plug the top hole (with rtv sealant). bench bled the master cylinder and bled the front and rear brakes. initially I was getting a 2 second grumble sound from the MC/comb valve, which might have been air int eh comb/valve cavity, but after a good 15 minute 2-person bleed job, the noise is gone and the system is holding fluid just fine.

I will definitely report back in a few weeks when i get a chance to road test everything.

QwkTrip

iTrader: (22)

On second thought I take that back. The pressure in the brake line would push the piston out with up to 100 lbs of force. The spring would end up fracturing into pieces, and maybe it would end up causing leaks too.

IROCZman15

iTrader: (25)

So, I finally got my badass driveshaft from Denny's shipped and installed in the car. I had an ignition issue going on with the car for a few weeks and I think it has been sorted out now (thread link: https://www.thirdgen.org/forums/tech...ease-help.html ) I got the car back on the ground and once I did the break-in session for the new moser 12 bolt rear end with it upon jack-stands, I took the car for a test drive to test this brake setup.

I set the wilwood valve to be full "out" or basically having the **** rotated all the way out. Checked brake fluid and lines for leaks, all was good. a few easy test brake-stops in the driveway, all was good. I began by slowly cruising around the residential neighborhood that I live in at a very low speed. all was good, but I could tell I would adjust the valve a bit. went over to a small parking lot at a local park and did a series of 30mph-5mph brake stops because I was testing the valve AND breaking in my new front HAWKS HPS brake pads. I cranked the valve several turns In on 3 separate adjustment sessions here at the park. I then went out onto some less busy public roads and did some more aggressive stops 45-5mph with moderate brake pressure, (also required when bedding in the Hawks pads). the front pads began to get gooood and grabby, but this caused the car to nose dive and lockup, leaving two nice thick black skidd marks fromthe front tires. cranked the valve in more, and continued the session. finally got it adjusted to a point where I feel happy with it FOR NOW.

I still need to get a 4 wheel alignment on the car since the new 12 bolt seems pretty close to where it should be, but only a computer wheel alignment will get it precise. I plan on then taking the car out on a rainy wet day over to a large parking lot and doing some heavy brake stop sessions and adjusting the valve accordingly. only then will I know my bias settings, when the valve is too far in/out, when the car wants to spin or twist, etc

So, all in all. this does work. The combination valve is completely gutted out. the metering valve is out and the nut/endcap is reinstalled with the center hole welded closed. the prop-valve is also out and the endcap has its hole welded closed also. a tapered bolt was used with some sealant to take the place of the "brake-light warning switch". DOT3 fluid and system bled multiple times. after a few more road sessions I might bleed it one more time. shall see. overall happy that this worked.

thank you to all of you who helped with advice and input on here, through private messages, and via text messages. much appreciated.