dreco

it was the little check valves, causing the issue. Bled brakes and no more drag. Now to put it all back together and test drive. FYI, the adjustable proportion vavle in the rear was put in to replace the stock pressure reducer valve. Thanks for all the info everyone.

Thanks for all the info everyone!! I'll takle this tonight.

I"m going to "check" on the check valve. I did not remove them. 1. Tell us what year Z you have as there are differences in the hydraulic systems. 1972 240z 2. There are residual pressure valves in the outlets of the master cylinder. They look like a piece of rubber with a spring. Remove them. Will Do 3. You should not have two proportioning valves (PV). Having two PVs can cause problems other than what you have mentioned here. If you have for example, a 72 240Z, and you have installed a PV in the rear then the stock PV should be removed. On later model Z cars you need to understand what the PV does before removing or modifying it. My understanding it that the stock 'proportion valve' (engine compartment) in a '72' really isnt one (only the restrictor valve in the rear) 4. The other question is why do you need a PV in the rear? 240SX rear calipers are typically undersized relative to most so called "front brake upgrades". So unless you are experimenting with high friction rear pads to fix front - rear balance issues a rear PV is not required with 240SX rear calipers. Installed it prior to going with the big brake kit up front. I only had the rear disc brakes at the time. 5. You can relieve pressure to the front or rear brake circuits by opening the respective bleeder on the MC if you need to limp home with dragging brakes. its up on jack stands. 6. In my experience, the front brakes will lock up after a few stops if the booster push rod is too long. It doesn't take much as the return port in the MC is small. The push rod can be adjusted without removing the MC from the car. Just unbolt it and push it to the side. I adjusted the rod all the way back just to make sure. There is play in the rod. 7. So remove the residual pressure valves, recheck the brake booster push rod length, and road test the car. I'll try the check Valves. I wouldnt think it would be possible for the brake distribution block in the engine compartment could hold any residual pressure, but it's the only thing I havent replaced.

its not that.. checked that.

I have modern motorport rear disc brakes with AZC front brakes. I have an adjustable proportion valve in the rear of the car. 15/16 master cylinder with stock brake booster. Brakes were fine for a while. Now a bad brake drag has developed in the front. I changed master cylinders, rechecked booster shaft clearance and brakes still drag (after one pump of the brakes). Both front calipers lock up. I can bleed on either side and it frees up both sides. Cant figure out where the residual pressure is coming from. Any thoughts? Could it be the stock proportion valve in the engine bay? or could the rear proportion valve be the cause ( I wouldn't think this due to being on the rear circuit.)

thanks!.. yes, I have the bolt in plates. I ground out the top hole a bit for more travel inward.

I'm running the BC bolt in coilovers with stock control arms and the adjustable control arm bushing. Running -2 degrees of negative camber in front and -1.5 in the rear. Plenty of oversteer. (275 tires, square set up)

I'd like to make it out there one of these days.

I'm late to this, but congrats!!! Thanks for posting the videos and pictures.

would not allow a pm. 214 206 5430

Eventually I'll be welding bars through the firewall, but i'll try this for awhile. We'll see how it holds up from my track excursions

keep me posted when you get in town. I'm up for putting a face with a name and talking Zcar shop over some beers. I actually live north of Dallas in Frisco.

I've driven my Datsun with a 3.0L stroker and now an LS6. I did like the sound of that L6 stroker motor, but I sure dont miss SU Carbs. The LS6 makes more tq at idle i think haha. I also love the driveability of my modern fuel injected V8. Add headers, 3 inch exhaust and a straight through muffler and it sounds amazing! https://www.youtube.com/watch?v=vwaXXpC9MK4 A Datsun is a blank canvas to me.

if I find time tomorrow I'll soften them up and go for a drive (day off). Be aware that I drive on Dallas streets and they are HORRIBLE.