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To keep or to bypass? 77 620 NLSV, with front disc swap.

Mad Dat

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So to start I won these brackets awhile back for my 77 620 to convert my front drums to disc, an finally decided to put them on. They seem to be the older style brackets I believe so they take the Honda or Isuzu rotors an hardbody 4x4 calipers. I had just realized this yesterday. I was using the 85 2wd hardbody hubs/rotor/ an calipers. I quick to learn those did not fit correctly an didn't even fit right in the spindle an had wheel slop. Funny thing I installed them an drove around the neighborhood testing the brakes an when I turned the calipers would engage cuz of all the wheel slop....wow that was dumb... anywho I now know I need the correct rotors etc.. I also am running the 1" wilwood MC so I know its plenty big but it is the disc/disc MC but they claim it's universal an will work with disc/drum, drum/drum aswell.


So when I would bleed the brakes I would get pressure no prob. (Did this multiple times also bench bled the master before installing) So I put the wheels back on, dropped her down an took off. Brakes were ok for a sec but then sink to the floor. Not realizing that I have a NLSV till yesterday I'm thinking this is my problem.


I'm not sure to try an delete the NLSV an add my own proportioning valve an lines, or I would still be able to use the NLSV with disc up front an drums in rear. I rly dont mind getting rid of the NLSV just to keep things simple an easy to bleed. I tried researching it but nothing about if it in disc swap.


Also last ? Is what hubs am I supposed to use with these disc swap brackets?

I will try an post some pics here soon. Thanks for reading.

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Looks like beebani's brackets. I bought the same ones... I have a 521 but the setup is the same.... these were the directions in his post...

Don't no about the nlsv thing...

And what do you mean when you asked what hub?.. it should be what you have stock on the truck...




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Oh ya that makes sense to use the stock hubs.


Thanks but I have already read that whole thing like 4 times to make sure it doesn't say anything about the NLSV. It's not on all 620s that's why I think it's not an issue for most ppl. I've read the way the NLSV works is with the load in your truck to compensate with the brakes an also the it's, it's own proportion valve the way it was made. So I'm thinking it might not work with the disc swap as it's kinda set for adjusting the proportion for drum brakes.


I'm wondering too if anybody has just bypassed it an used there on proportion valve.

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It seems like we need something,. the way I read it beebani seems to imply the 620 has a proportioning valve, which is that thing you have, he says the 521 need as 280zx or willwood adjustable... my 521 had nothing just a couple t blocks to divide the lines.. so I'm running a similar dual master and I have a willwood proportioning valve for the rear... I am in the process of bolting my stuff on too. Lines are next.. i don't see why you couldn't delete that and install you own adjustable.. It would be just like following the 521 install notes....

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Ya that's kinda what I'm thinking. It's hard for me to even follow the brake lines after the MC. They go into like 7 blocks an no way to tell witch is in or out. Ide try an use what I could or just completely re-do all the lines witch would be kinda a pain with no lift an in the gravel..but hey that's datsun for ya lol.

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Ok your saying you would leave the NLSV an just add a 10lb pressure valve for the rear drums?


I installed a 2lb when trying to diagnose the problem an seem to help but barely. But there's too many things I need to straight out before trying again. Like the wrong rotors an such. That was prolly giving me alot of problems as they would just keep trying to re adjust themselves an not giving me any straight answers cuz I started off wrong lol. Also not bleeding the NLSV is prolly why I'm not getting any pressure.


So I need to get the parts on an then bleed everything correctly an possibly it will just work with the NLSV. Maybe add a residual pressure valve in there if seems to need it.


Is there a thread out there on how to disconnect the NLSV an keep most of the brake lines that you can?

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I had 4 wheel discs on my 73 and did not use a proportioning valve. Truck had no NLSV. I used 15/16 master from 280 ZX

Right on. Thanks.


Ya Imma try an delete it but just not sure how. I looked at it this morning before work an was able to fallow the lines to it an from it easier than I thought. Think I just need a block or connector down there where the valve is at.

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Ok got the NLSV off an brakes working good.


So I took some pics an tried to make it simple if anybody else is wondering how to delete the NLSV.


First here's the valve an all its lines.




Next is me trying to explain where some of the lines go.



Here's what it should look like when u get the valve off.



Next is where one of the lines, (Red line) goes back to the front or from the fronts the NLSV. I'm not sure if it's going to the valve from the front or if its a return to the fronts from the NLSV.

I'm wondering if u can hook this line back together with the rears an keep the system all tied together for the whole safety side of it all where the two reservoirs actually feed both lines.

But I just deleted it an plugged the whole so now the fronts are separate from the rears.



I also wanted my brakes to be separate so I can install a Hydro E-brake. The rears have to be on there own system not tied in with the fronts. So removing the NLSV made this a little easier. You wouldn't have to remove the NLSV for an E-brake but u would have to do something with the front line that goes or comes from the NLSV.


So the following pics are for installing a Hydraulic E-brake in a datsun 620. This should be fairly general so u would be able to use this info on your own rig whatever it may be.


Ok I will start from the master cylinder aka: (MC)




I did use a proportioning valve but not sure if I rly needed it. It's simple an fun to use with the E-brake especially because u can make it more sensitive (more brake) an less sensitive (less brake).


Next is the e brake itself. It's actually rly simple to install. U take the line from the rear MC an go directly into your e-brake. Then from there goes directly into the rear line.




Now take the line an splice somewhere for the rears.

Like this




Ok now you should be able to delete the NLSV easy an know what to do.

You should also be able to install a Hydro E-brake with ease as well.


I know it wasn't super clear an I will answer questions but I'm sure y'all can figure it out from here.

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