joeygoz1 Posted August 17, 2008 Share Posted August 17, 2008 I recently converted my OEM solid disk front rotor and rear drum brakes to 03 Ford Cobra brakes, 13" fronts and 11.5 " rear, with a proportion valve in the cab. Also I gutted both OEM bias proporting valves to make as a pass through one located on the firewall and another located near the driverside rail near the shock tower. I've noticed on later z's that only one bias valve were installed from the factory compared to what I have on my z. In anycase I'm expericing a bad spungy brake pedal and have to pump the brakes in order to build pressure. Any ideas would be greatly appreciated. Quote Link to comment Share on other sites More sharing options...
Nigel Posted August 17, 2008 Share Posted August 17, 2008 I'm not trying to be mean here, but you really should take the time to understand what these parts do before you start messing with them, especially when it comes to brakes. First of all, those two parts you gutted are not both proportioning valves. Only the one on the firewall is. The one on the shock tower is a brake pressure warning switch that warns you if there is a pressure loss to the front or rear brakes. So, by gutting it, you've just disabled that safety feature. Secondly, by gutting both, you've effectively tied the front and rear brakes lines together at two points (nether should be), bypassing another safety feature. The front and rear lines are kept separate so that a failure at one end will still allow you to have brakes at the other. You need to reassemble the warning switch and as for the proportioning valve (on the firewall), it should be removed and the gap in the lines should be spliced together. The proportioning valve uses pressure to the front right caliper to regulate pressure to the rear brakes lines, so that's how you tied the lines together there. This may not necessarily explain your spongy pedal, but you should definitely address these mistakes first. Nigel '73 240ZT Quote Link to comment Share on other sites More sharing options...
v8dats Posted August 17, 2008 Share Posted August 17, 2008 not much help here but do you have anymore pics of the car? Quote Link to comment Share on other sites More sharing options...
blueovalz Posted August 17, 2008 Share Posted August 17, 2008 I would strongly suggest the removal of the two duplicate postings before moderator comes crashing down on you. One post in the appropriate forum (this one) is all that is needed or allowed. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted August 18, 2008 Share Posted August 18, 2008 Correct, Terry and Nigel. Joe and I've been communicating via email and things are sometimes tough to understand on both ends... The thing is, Joe didn't want to replace all the lines and tie the front circuit together and the back circuit together, voiding both the factory bias valve and the safety switch. My recommendation is to get rid of all of the parts associated with "safety" and "bias" from nissan and close off the front and rear circuits from each other... Run the Bias valve off the rear line from the master, and you'll be good to go. As I said in my email, Joe, I've got some unions in metric sizes you can have to make those connections to isolate the rear from the front, and just do away with them... Also, What Terry said is right... One not per topic in the right category... Mike Quote Link to comment Share on other sites More sharing options...
joeygoz1 Posted August 18, 2008 Author Share Posted August 18, 2008 Okay thanks for the replies. I do apologize for the the multiple posting, was experiecing server problem with uploading the pictures and for some reason or another was able to post the pics via this catagory, which turned out to be the third try. I'm new to this forum so please work with me and I will remove the other related threads just having a little difficulty doing so, some direction would be greatly appreciated. As for the bias valve located on the firewall will be removed and lines will be tied in properly and will work on the safty pressure warning switch will most likely remove that too. Thanks again. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted August 18, 2008 Share Posted August 18, 2008 Joe, I deleted them for you... Give me a ring tomorrow and we'll go over what I think you can do to eliminate the issue all together. This is a real easy fix... You'll be driving the car in two hours, max. Mike Quote Link to comment Share on other sites More sharing options...
Mikelly Posted August 30, 2008 Share Posted August 30, 2008 Very happy to report that we've got Joe's car squared away and his cobra brakes are sorted/ no longer leaking, and all OEM bias/brake switches have been removed from the system. BIG grin on his face after the test drive today! Mike Quote Link to comment Share on other sites More sharing options...
joeygoz1 Posted September 4, 2008 Author Share Posted September 4, 2008 Yes indeed a grin from ear to ear couldn't be happier. Thanks for the help Mike. Quote Link to comment Share on other sites More sharing options...
DavyZ Posted September 4, 2008 Share Posted September 4, 2008 I recently converted my OEM solid disk front rotor and rear drum brakes to 03 Ford Cobra brakes, 13" fronts and 11.5 " rear, with a proportion valve in the cab. Also I gutted both OEM bias proporting valves to make as a pass through one located on the firewall and another located near the driverside rail near the shock tower. I've noticed on later z's that only one bias valve were installed from the factory compared to what I have on my z. In anycase I'm expericing a bad spungy brake pedal and have to pump the brakes in order to build pressure. Any ideas would be greatly appreciated. Very happy to report that we've got Joe's car squared away and his cobra brakes are sorted/ no longer leaking, and all OEM bias/brake switches have been removed from the system. Joe, so based on what you posted and what Mike posted, the system is as it was, only minus the OEM bias switches. You guys just bypassed or removed them? Nice work in getting that sorted so quickly. Davy Quote Link to comment Share on other sites More sharing options...
Mikelly Posted September 4, 2008 Share Posted September 4, 2008 This system realy works well if you remember you'll need to remove the OEM bias and pressure switches and install Ts and unions, along with a manual bias adjuster. I personally think this system is better, and certainly more cost effective, with a functioning E-brake, than the Wilwood setups being sold by others... And the OEM mustang cobra rotor setup sold by most of the popular race car suppliers will be a direct bolt on! Mike Quote Link to comment Share on other sites More sharing options...
heavy85 Posted September 4, 2008 Share Posted September 4, 2008 Mike - what do you mean by 'direct bolt-on' and will these fit 15" rims? Thanks Cameron Quote Link to comment Share on other sites More sharing options...
Mikelly Posted September 4, 2008 Share Posted September 4, 2008 Cameron, I shouldn't have said "direct bolt on"... You need to have adapters made for the calipers in the front and buy the early 79-81ZX caliper bracket for the rear and then drill it out to fit the Mustang Caliper. Once you've gone thru all the "hoops" of sourcing the caliper adapters, and proper hub for the front (Jamie Taylor had a run of them made, but they're out of production now, but Ross may have them) You can then just run all the Ford SVT Cobra stuff from 1999-2003. If you can track down all the parts, it's well worth it... Or just buy the kit from Baja... I fully believe that the OEM Mustang brake setup (it's a five lug deal) is the best way to go for these relatively light weight cars, and the OEM form parts source makes daily driver parts a snap. I don't think these will fit the 15 inch wheel. The front rotor is a 13inch rotor. I'm not even sure you could squeeze a 16 inch rotor on it. Mike Quote Link to comment Share on other sites More sharing options...
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