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79 620 disc brakes on 73 help!


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#1 Cordova Kustoms

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Posted 09 August 2017 - 10:45 AM

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...

#2 ]2eDeYe

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Posted 09 August 2017 - 10:50 AM

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. 


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Whenever I think that I'm out of my mind for putting this much time and money into an old Datsun, all I have to do is look some of your threads to know that I'm not nearly as whack as you are.

You're going to skin a few knuckles, stand up too fast and bump your head, hunt around the floor for the nuts and bolts you dropped, invent a few new cuss words and when you're finished you'll say "That wasn't so hard after all!"


#3 Cordova Kustoms

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Posted 09 August 2017 - 10:53 AM

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

#4 wayno

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Posted 09 August 2017 - 11:58 AM

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.


 

 

 


#5 Cordova Kustoms

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Posted 09 August 2017 - 12:57 PM

Ahh very interesting. Anybody need to buy some rebuilt uppers?? Hahhh...ok that's very helpful information.

#6 wayno

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Posted 09 August 2017 - 01:14 PM

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


 

 

 


#7 Cordova Kustoms

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Posted 09 August 2017 - 01:32 PM

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!

#8 wayno

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Posted 09 August 2017 - 04:03 PM

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.


 

 

 


#9 Cordova Kustoms

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Posted 09 August 2017 - 04:52 PM

Nahh no donor frame. I'll try and see what I can do. Nan what a pain in the ads this little truck is!

#10 wayno

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Posted 09 August 2017 - 08:11 PM

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?


 

 

 


#11 Cordova Kustoms

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Posted 10 August 2017 - 12:15 PM

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.

#12 wayno

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Posted 10 August 2017 - 04:31 PM

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.