My 1971 521

[wayno]

If you want to get your calipers super hot, maybe even start a fire leave the drum brake residual valve in there.

I think Mike Klotz told me that the 1979 Z car had disc brakes all around and to use that master brake cylinder.

[thisismatt]

Yeah, maybe tell what master is in there now? 

[d.p]

56 minutes ago, thisismatt said:

Yeah, maybe tell what master is in there now? 

Dual from a 620 I think? Been so long since I bought it hard to remember.  Was told 81 zx was the one to get for discs all around and that it fits on a 620 so should fit on a 521? 

[thisismatt]

zx 15/16 masters getting hard to find, but yeah it would be set up for disc front & rear.  Wilwood has a 1" but I heard they're discontinuing them 🤷‍♂️

[d.p]

This is all that’s in the front (rear outlet) of my MC.  Is that the residual valve? 
 

after taking that out it leaks like a sieve from the outlet port. 

Edited May 15, 2022 by d.p

[thisismatt]

Probably just want to take out #20 and leave the rest

 

 

[thisismatt]

although 23 should be all you need as long as it's torqued tight enough

[d.p]

This fucker?

 

 

[datzenmike]

 

29 minutes ago, d.p said:

This is all that’s in the front (rear outlet) of my MC.  Is that the residual valve? 
 

after taking that out it leaks like a sieve from the outlet port. 

 

This is a Tokico master. 620 did have these but I have only ever seen Nabco on Datsun/Nissans. The disc with the holes and the cup under it are the valve with the spring pressing to close it and hold the residual pressure.

 

You can remove the valve and simply plumb an after market 2 PSI residual valve.

 

What diameter is the master? The '78-'79 disc brake masters were 13/16" and will work, though a larger front caliper and rear caliper will demand a lot of fluid. The travel of the pedal will supply this but will have to move a longer distance to get the same volume/PSI as the stock brakes. (you can't get something for nothing law) This extra travel will seem like the brakes are mushy. You have a brake booster? if yes you won't notice the extra effort of a 2 sizes larger master, otherwise it's like stepping on a brick. If you can find a zx 15/16", it has to be a '79-'81 for the vertical bolt pattern to fit the 521. The '82-'83 were horizontal though I have seen a thin adapter on the booster that converts horizontal to vertical pattern.

 

15//16" horizontal mounting bolt pattern...

'81-'84 Maxima

'83-89 S12 200sx

'87 and up Hardbody*

 

*You might look at getting the D21 master and booster as a unit. The car boosters are huge diameter but the Hardbody ones look smaller and may clear the tight fitting 521 clutch master right beside it. Worth a look.

[Stoffregen Motorsports]

2 hours ago, d.p said:

Dual from a 620 I think? Been so long since I bought it hard to remember.  Was told 81 zx was the one to get for discs all around and that it fits on a 620 so should fit on a 521? 

Ok, at least you have a dual master.

 

I would try removing the valve and running without it, and see how you like it. If you can get the brakes bled properly, give it a shot. What they say about head pressure is true. Since the master is two feet higher than the calipers, there will be some natural head pressure there.

[d.p]

Back on the road and the only issue is my parking brake doesn’t work very well.  Meaning I pull it and the truck will roll so I have to much slack on it?   I had to spin the cleavis way out to even be able to attach the rear section of cable once I attached them rear discs so not sure what that means.  
 

Brakes have a little more travel to them but work just fine. 
 

 

[mrbigtanker]

Nice picture, looks good. 1" down on the back more though.

[d.p]

15 minutes ago, mrbigtanker said:

Nice picture, looks good. 1" down on the back more though.

I agree just not sure how unless I get bigger blocks?  I think I have 2 1/2 or 3 1/2” already.  

[d.p]

Oh shit I totally forgot that I have 720 4x4 leafs but gave up on installing them because I didn’t want to fuck with the stock shackle bushings.  

[thisismatt]

Looks like the next project...and go!

[d.p]

54 minutes ago, thisismatt said:

Looks like the next project...and go!

 
I’m ready for an easy project.  Not sure swapping leafs would be easy.  Don’t see many people that have done it and the one dude who did was asking me questions about it.  I’m probably the wrong guy to ask about it lol. 

[thisismatt]

Come on, make the guide 😂

[d.p]

Fuuuuuuuck that.
 

Next project is side mirrors.  Ordered these from Riley in the hopes of getting a passenger side mirror.   

[mrbigtanker]

Dude throw the 4x4 crap away and order new ones from summit or from bell tech leafs, they will bolt right on, you might have to redial the bolts because the 521 it not really centered. And before anyone opens there mouth the 4x4 boys do it all the time with no issues. New hole has to be more then an inch away. 

[mrbigtanker]

https://www.belltech.com/products/belltech/lowering/belltech-3-quot-drop-rear-leaf-spring-each-5974.html

[mrbigtanker]

That I believe fits, I don't remember the part number but it was a later model.

[d.p]

15 hours ago, mrbigtanker said:

Dude throw the 4x4 crap away and order new ones from summit or from bell tech leafs, they will bolt right on, you might have to redial the bolts because the 521 it not really centered. And before anyone opens there mouth the 4x4 boys do it all the time with no issues. New hole has to be more then an inch away. 

 

redial the bolts? What the difference really between my 720 leafs and new bell techs other than their age?  Remember I am doing all this shit in my garage so whatever I do has to be done with regular old hand tools and occasional outside assistance.  

[thisismatt]

Think he meant redrill...the alignment hole where the leafs attach to the axle

[d.p]

6 minutes ago, thisismatt said:

Think he meant redrill...the alignment hole where the leafs attach to the axle

 

Ahh ok, I just googled this shit and someone on here mentioned the mounting hole was 3/4" if I went that route.   You linked to these back in 2014 and they come with bushings already pressed in so that is nice.   

 

https://www.amazon.com/Street-Edge-Lowering-1983-1997-Hardbody/dp/B083C1S13Y

[d.p]

Can someone help me understand the parking brake? Worked fine with my drums but now it’s not working….meaning when I pull the handle the rear wheels till spin.  
 

Like I said previously I had to spin the rear most cleavis out to get that rear cable that attaches to both calipers to reach.  So I assume the disc brakes moved everything back towards the rear.    
 

There seems to be too much slack in the rear most cable.  I can’t spin the cleavis in (towards the front of the truck) anymore because then the bracket won’t line up it and I can’t get the pin through.  When I pull the brake I can see the wire tightening up but obviously not enough.  I also noticed it was hard as shit to manually push the parking brake in at the caliper ends.  
 

this is what I’m working with: