Jump to content

79 620 disc brakes on 73 help!


Recommended Posts

Hey guys. I accidentally posted this in suspension too sorry! So I got a complete disc brake set up for my 73 which is great but I just noticed my strut rods are threaded on both ends. The 79 lower control arms bolt to the strut rods using two nuts and bolts. Anybody know if the strut arms for the 79 will work on my 73? Is the 720 stuff the same? Any help is much appreciated...

  • Like 1
Link to post
  • Replies 16
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

They will not bolt up. You will need custom uppers to get the length and angles correct. 

 

BEEBANI is a member her that offers kits to swap to later style ball joints. 

 

720 stuff is similar to the 79 620, but not identical. 

  • Like 1
Link to post

So 79 620 uppers won't work on the 73??

 

What you are trying to do isn't possible without modifications, ball joint joint front ends do not bolt onto kingpin chassis/frames without quite a few modifications, this mod is not for the faint of heart, it was interesting for me for several years till I figured it out on my 71 Datsun 521.

I used 620 lower arms and tension rods, modified(extended) 720 upper control arms, originally I use 620 spindles/disc brakes, but now I am using 1990 V6 Hardbody disc brakes(vented/dual piston calipers), there are several things I would do now that I didn't know about back in the year 2000/2001 when I did this conversion.

I would drill and thread the upper control arm mounts to except 720 mount bolts, and instead of extending the upper control arms I would shorten the lower control arms.

If what you are trying to do was easy, everyone would do it, but it is not easy at all, by the way the upper control arms have to be reversed, you have to put the left side on the right, and the right side on the left, this puts the castor close to where it needs to be.

Again I will say this, this is not for the faint of heart, I had the upper control arm mount bolts break several times over the years while I was driving my truck, admittedly it is my work truck and I load it well over what most would consider safe, it works for me till one or both them mount bolts break, it very unnerving when the front of the truck drops to the ground unexpectedly, I had it happen going 30mph once and it sucked, lucky for me it never happened at freeway speeds, this is why I say drill and thread the upper control arm mount bolts to except the 720 mount bolt, the upper control arm shaft holes are that size already, that way you don't have to sleeve the holes which when them bolts break you lose the sleeves half the time, it just sucks on so many levels when them bolts break.

  • Like 2
Link to post

It can be done, I would never do it again myself though, there are much better ways to do it now.

Mike Klotz is putting together a complete setup right now that I am positive will work great and be correct when you get it, just not sure how soon he will be offering it to everyone as his R&D is a long process, but once installed you will not have to pull it apart again as it will be correct when you get it.

If your kingpins are good Mike also offers a disc brake brackets for them, that is really easy to install and you can buy all your brake parts at the local auto parts store, his kit uses 1985 Nissan 720 disc brake parts as I recall.

 

Mikes contact info   bluehandsvideo@frontier.com

  • Like 2
Link to post

See I got the complete changeover from a 79 minus the radius arms and already rebuilt everything. Klotz makes good stuff. I gotta see how much of this I can use before I bury myself first!

  • Like 1
Link to post

I call the radius arm the tension rod, I used the 620 tension rods, they fit just fine, I also used the tension rod bushings, and it is a tight fit in the 521 which I would assume your early 620 is almost exactly the same as my late 521, the alignment shop told me I had everything within 2 degrees when I finally figured everything out.

It took me over a year to figure out to reverse the upper control arms(right on left/left on right), once I did that everything just felt good, before I switched them it was difficult to get the truck to go in a strait line and cornering was very interesting, it wanted to turn by itself once the turn was started.

There is no getting around extending the upper control arms or shortening the lower control arms, it cannot be aligned if you don't, the upper arms are around 5/8ths of an inch too short(720 upper control arms), the 620 arms are difficult to work with because of the bump stop pads on them, it is much easier to lengthen the upper control arms than it is to shorten the lower arms, I have done both ways.

If you don't drill and re-thread them upper control arm mount holes, then you might as well dig a hole to be buried in, eventually them weenie bolts you have will break and if your going freeway speeds when it happens it could get real ugly, like rolling the truck ugly if you go into a ditch.

I never did drill mine out, they broke so many times and I tightened them so tight trying to keep them from coming loose that the holes stripped out and I bought really long very strong bolts that stuck out the other side by the shocks, I then added washers on the back side and tightened them up till the other side collapsed and seated on the back side of the shock tower, the driver side upper control arm has not came loose or broke since, but it is not a proper fix, some day when I have the engine out I will drill them holes and thread them for the 720 mount bolts.

Do you have the front 1979 620 clip(frame) to weld to your early frame, that would be way easier, you don't have to re-invent the wheel that way.

  • Like 2
Link to post

They are not a pain, we make them a pain when we start changing them, the best way to do that is single small modifications that you work all the bugs out before making the next modification.

What you are attempting to do is hard if you have never done it before as you are just guessing like I was when I did it.

How far are you into this modification?

  • Like 2
Link to post

I've done plenty of early GM and Ford stuff just not the imports. I think at this point it's going to wait. The truck isn't apart and as much as I'd like to I can't spend any more money on it right now. Thanks for all the advice guys, much appreciated.

  • Like 1
Link to post

GM and Ford have major aftermarket support, most our Datsuns don't, especially the early trucks, very few make aftermarket parts for them.

What you want to do can be done, I did it and that truck is still on the road to this day, it's likely one of the toughest 521s out there.

I was even complimented by my helper a week or so ago about how much power my truck had and how well it handled towing a trailer while the flatbed was filled to the top with wet moss/debris, he thought it had a V6 in it, but it is only a 4 cylinder.

The key is having a set of extended upper control arms, the 720 upper control arms need to be 3/4s of an inch longer than stock, the rest can be jury rigged to a point.

  • Like 1
Link to post
  • 2 weeks later...

The tower that the upper control arm bolts to in the 79 is angled and the ealier drum brake 620 is is straight with the frame rail.  I have my brother working on a jig to take the angled mounts off later trucks and weld them on older trucks.

 

He will be designing new towers for me to run coil overs instead of the torsion bars.  Beebani makes adjustable control arms and also adapters for coil overs that work fine.  I just do not feel the thickness on the original tower material is heavy enough to take years of abuse from coil overs.

 

When my brother finishes these items I willl post it up on the on the DIY section of Ratsun.

  • Like 2
Link to post

When I was doing my coilover and disc brake conversion, I really wanted to cut that tower off and remount it like the later 620s. A jig would have been very nice. 

 

I agree about having reservations about the stock tower being strong enough to support the suspension. When I welded on my beebani coilover mounts, I raised them up a bit by putting a piece of 1/4" plate along the side of the tower extending from the frame rails up to the top of the tower. Sorry, hard to describe. It had about a 45 degree bend in it. I think that will better tie and support the frame rails to the top of the tower. 

  • Like 1
Link to post

The tower that the upper control arm bolts to in the 79 is angled and the ealier drum brake 620 is is straight with the frame rail.  I have my brother working on a jig to take the angled mounts off later trucks and weld them on older trucks.

 

He will be designing new towers for me to run coil overs instead of the torsion bars.  Beebani makes adjustable control arms and also adapters for coil overs that work fine.  I just do not feel the thickness on the original tower material is heavy enough to take years of abuse from coil overs.

 

When my brother finishes these items I willl post it up on the on the DIY section of Ratsun.

 

Seems like a lot of work when you can just lengthen a set of 720 upper control arms 3/4s of an inch and then put the left side on the right and right side on the left, since the arms are offset, that puts the offset towards the back like twisting the shock tower does and puts the castor right about where it is supposed to be.

It's easy to make a set of extended arms if you have 2 sets of them, you just have to cut them in the correct spots and then weld them together.

Also if your lowering your truck, instead of switching the arms to the opposite sides, just flip them upside down after grinding the lip off where the ball joint mounts to the arm.

As I have said in the past, I would drill the upper control arm mount bolt holes and thread them to use the 720 mount bolts instead of using them weenie 520/521 mount bolts, I have never done this myself yet, I made it work with much harder bolts with lock nuts and big washers on the back side since my threads stripped out on the driver side.

I did this on my 521 frame 15 years ago when I converted over to 620 disc brakes, since then I converted to 1990 hardbody V6 dual piston calipers with vented rotors, they bolted right in.

  • Like 1
Link to post

You are correct Wayno your way is easier.  Have you tried using lowered spindles qith either of you 2 setups?

 

2wheel-lee I would recommend doing the same thing as you on strengthening the towers when using Beebani's coil overs mounts.

 

I like to challlenge my brothers fab skills so this is how we will proceed.

Link to post

You are correct Wayno your way is easier.  Have you tried using lowered spindles qith either of you 2 setups?

 

2wheel-lee I would recommend doing the same thing as you on strengthening the towers when using Beebani's coil overs mounts.

 

I like to challlenge my brothers fab skills so this is how we will proceed.

 

I have drop spindles, but I do not plan on lowering the 521 work truck with all the suspension mods I have been describing, it will stay as it is as long as it is a work truck.

I made drop arms for the 520 ute(over a 2 1/2" drop), if I put the drop spindles on it the drop arms would almost be resting on the ground so that isn't going to happen, it's low enough anyway.

I am considering using the 2 sets of drop spindles I have on the 521 turbodiesel and the 720 turbodiesel, just have not got around to it yet, if I use them I will have to notch both the rear frames, I have the pipe I need to do that to them like I did the 520 thanks to you, just have not got around to it yet, too many projects.

Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.