Hi All, I am a new member to this forum and I have a 1970 Maverick 4 lug and drums all around. I am looking at a Wilwood front disc brake kit (to swap to 5 lug). Part number is 140-13477. Does anyone have any experience with this kit?
I just bought that same kit from summit. Still in box so not installed yet. I decided on that kit because. 1. I'm able to use stock spindle. 2. Installation seems simple per video. 3. My drum system is shot and suspension need rebuilt so now or never. 4. Price was right. 5. Upgrade! Lots of guy here doing granada dics brake swap as wells. I did on mustang 10 or so years ago. Granada swap was easy too but expect to swap stock spindle. Still working great!
I was able to reuse the master cylinder, however, I ended up using an ebay kit and not the wilwood in order to save some money. Everything from the ebay kit bolted up perfect but it looks like it is out of stock. Here is the link to the kit I used. https://www.ebay.com/itm/181951874311 Hope this helps.
A lot of people reuse their drum brake masters but there are specific masters for each system and it is not something I choose to chance. Two specific differences that cause me concern are the residual pressure valve and the size of the reservoir. Neither will stop the system from functioning but the residual pressure valve will hold some pressure in the line. It does that to keep the seal on the cups in the wheel cylinder so they won't suck air back in when the pedal is released. In drums, that light pressure is held against the springs, on discs it will keep the pads from fully retracting from the rotor which could cause the pads to wear prematurely. The reservoir size for discs is larger because calipers hold a lot more fluid. As the pads wear the level drops. With drums the wear is accounted for mechanically not hydraulically so the reservoir see minimal level change. Your choice but for me the money for the correct master is a no brainer.
Defeating residual valve is a piece of cake, pierce the rubber cap with a paperclip. Can be inserted through port. For MC reservoir, yeah you should check fluid more often. Yes if valve isn't pierced or removed, discs will drag noticeably using a drum MC. Back in early '80s, I drove a Ranchero with drum MC for about four years after I converted to discs(yep pierced cap). Till I convert to power, doing same on my Fairlane. Pict of Ford residual valve.
They would without the valve, that's why it's there. Had that very issue with the proportioning valve on my 68 GTO. The seal would not let fluid escape but every time you let off the brake it pulled air into the valve. Had to bleed them every week, I chased it for months before it was suggested I replace the valve. I bypassed it and everything worked as it should. Ended up taking it apart and there was a spring on the seal lip that failed so it sealed with pressure on it but when there was none it sucked air back in.
That is not why the valve is there. It is used to keep pressure against the return springs inside the drum. This means the brakes engage faster with less pedal travel. Most disc brake systems do not require a residual valve. However, a 2-PSI is used when the master cylinder is lower than the calipers. When the master cylinder is mounted on the firewall, it is usually higher than the calipers. Gravity keeps the fluid from flowing backwards. In this case, a residual valve is not required...
Somehow that seems unlikely...Doesn't leak with 300lbs hydraulic pressure but allows air past seals? Must be a GM thing. Due to brake light warning light, a proportioning(or pressure differential valve) has seals to prevent external leak. It does happen, usually through the pressure switch that operates dash lamp, those have no seal function.. Residual valve is fully contained within hydraulic system(inside port of MC). If failed on drum brakes, there will be excessive pedal travel, it can never leak externally or pull air. It isn't necessary or even desirable on disc.
I only know what they taught in school when I went on to tech school and that is what they told us. They said due to the design of the seals inside the wheel cylinder they needed residual pressure to ensure they maintained a seal. As the master retracted it could create negative pressure without it pulling air in. Never gave it a second thought until I had my issues. The valve I was talking about that I had issues with was not the residual valve, I am well aware they can't pull air into the system. In 67 and 68 GM used a bastard valve to delay pressure to the calipers. This was prior to them incorporating it into the distribution block. It mounted at the master and that was where air was introduced into the system on my GTO. Under that rubber bulb is a shaft and that is where my car sucked air into the system.
There is a residual pressure valve for the drum brakes as explained in my previous post, and there is the proportioning valve which is for reducing rear wheel lock-up. Neither are for "sealing" or keeping air out of the system. Whoever told you that was quite mistaken...
