Duke's '72 510 (Carbed KA Autocross/Hillclimb car)

[Duke]

For the last 3 or so years I have been using a coilover setup that is woefully inadequate.  The shocks were a set of old Carrera's that I received in a box when I purchased the car.  They worked, but they had some issues.  I had no clue what the valving was, they were mounted in the typical 510 fashion (poly bushing on the bottom and bayonet on the top) and one of them had recently started to leak.  I decided to upgrade to a Koni 30 series damper, similar to what can be found in the Ground Control kit.  I did this for multiple reasons, but the main one is that circle track parts have a very good industry support, so if I decide to upgrade/change valving in the future this should be pretty simple.  With this though I wanted to make some changes.  Where the coilover mounts to the control arm people typically use a poly bushing to slid over the stud.  If you have ever looked at one of these bushings while the car is on the ground you can see that they deflect a pretty good amount under the weight of the car.  I wanted to use a solid mount on this end.  If you have ever measured the stud that the shock mounts to on the control arm you will find that it is about an RCH over 5/8”.  I figured if I mounted a 5/8” spherical bearing on the end of the shock shaft (typically with circle track shock uses a 1/2” spherical bearing here) I could hone down the stock shock mount to fit.  So I purchased a couple 5/8 spherical bearings and the associated weld cups and modified the normal Koni shock shaft mount to come up with this.






For the upper mount I wanted to forgo the stock bayonet style mount and use the 1/2” spherical bearing on the Koni shock.  To achieve this I cut out the old shock tower top and made a new one to accept a 1/2” through bolt.






This all ended up taking a little longer than expected because I got into a pretty bad case of “while I'm in here.”  I ended up stripping all the undercoating from the rear wheel wells, the paint from the trunk floor and rear seat area (both areas were pretty ugly), stitch welding the shock towers, and redoing the plumbing on the rear half of the fuel system.  In the end though it was all worth it, and the rear interior area of my car is much prettier.

Back to the coilover install.  My initial impressions are very positive.  I have the shocks set at the softest of their 4 settings and the car feels very well balanced.  Mid-corner bumps have a much smaller affect on the attitude of the car and it feels much better in transition.  I was also a bit concerned that the solid mounts would be a bit clunky, but things have been silent so far.  I'm looking forward to seeing how these perform at the first auto-x of the year in about a months time.

[q-tip]

Looks good! Glad you like the konis with the inverted springs, makes me more confident running my ground control setup.

[]2eDeYe]

As always clean and functional upgrades. Nicely done :cool: 

[S30Jay]

Glad I found this, great build. Car is lucky it found you.

[Stoney]

Have you got any interior pics lately? how spartan is it? What seat are you using?

 

Impressive upgrade with the rear coilovers, is anything original leftover in the rear end?

[datsunhead]

The lower coil over mounting bolt should have a big flat washer on it to keep the coil over captive if the spherical bearing comes out. Most sanctioning bodies require it. Good insurance for a nice car.

[Duke]

 Thanks for all the positive comments guys!  The car is slowly getting to the point where I'm pretty pleased with every aspect of it.

 

Have you got any interior pics lately? how spartan is it? What seat are you using?

 

Impressive upgrade with the rear coilovers, is anything original leftover in the rear end?

The interior is pretty bare.  Dash, 2 seats, passenger floor mat, roll bar, and not much else.

 

I'm pretty sure that there isn't a single original thing left on the car :devil:! (At least mechanically)

 

The lower coil over mounting bolt should have a big flat washer on it to keep the coil over captive if the spherical bearing comes out. Most sanctioning bodies require it. Good insurance for a nice car.

 

There is, you just can't see it in the picture.  It is bigger than the OD of the spherical bearing but hides behind the massive spherical bearing cup.  Thanks for the concern though :thumbup: .

[Duke]

The first autocross of the year was this last weekend.  The car performed awesome, but I can't say the same about the driver.  It took me a few runs to remember the limits of R compound tires, and once I did, I couldn't get a clean run to save my life.  On the plus side the new rear coilover setup felt much better than the old.  The venue where we run has pretty horrible pavement, and the car was much more settled when going over the rougher areas.

 

Here are some pictures from the event courtesy of Bob Jenkins.

 

 

 

 

I've got some more things happening with the car so there should be a few updates within the next few weeks.  

[skyblue]

it was awesome seeing your car in action. see you at the next one!

[Eagle_Adam]

16 pages of fucking epic awesomeness!!

 

What a build!! Reading back thru it all was suck a good use of a few hours :D

 

That carb'd KA just sings man

[skyblue]

I forgot I took this from last month. Had to cut it short cause the next guy hit a cone and I had to go grab it.

 

[Duke]

I forgot I took this from last month. Had to cut it short cause the next guy hit a cone and I had to go grab it.

 

You had to get the bad run!  I almost lost it in the first turn.  Will you be out there Saturday?

[skyblue]

Haha. I thought that was on purpose. Yea I'll be there. See you in the morning.

[Duke]

What's the saying? If it ain't broke, build a better and lighter one to replace it...I'm not sure if I got that one right…

 

On that note I recently built a new set of lower control arms and T/C rods. My main motivation behind this was basically that I wanted to make something, and these seemed like a good candidate for redesign. My secondary motivation was that I wanted to try and use the 280zx steering arms that I had laying around to see what kind of a difference they would make with steering feel. The whole project kinda snowballed, as they often do, into a fairly comprehensive front suspension rebuild.

 

For the LCA I wanted to build a full tubular setup that used a 5/8” spherical bearing in place of the stock ball joint and eliminated the sway bar mount (if you recall my sway bar is now mounted to the strut tube) and moved the T/C rod mount outward to better triangulate the forces on the control arm. The inner pivot is the same 5/8” rod end from my previous setup. The main tube is 1”x.083 wall DOM tubing. The T/C bracket is made from 1/8” flat bar. The T/C rod mounts on a single 3/8” AN bolt. The single mounting point of the T/C rod allows it to pivot when the LCA's are lengthened, eliminating the binding that can happen with the stock setup. For the T/C rods I used 3/4”x.188 wall DOM, drilled and tapped on the end to accept the M14x1.5 inner tie rod end that I use as the T/C pivot.

 

 

 

 

 

 

You can see how much simpler they are when compared to the stock arms. I never did weigh them, but feeling them side by side there was a noticeable weight difference.

[Duke]

For steering arms I have a couple of options. The first is a set of stock 510 arms (thanks Icehouse!) that I reamed out the stock tapers to 5/8” straight for the ball joint and 1/2” straight for the tie rod. I did the same with a set of 280zx arms, but because of the larger holes for the ball joint and steering arm, I had to partially weld up the holes before reaming them. My reason for going to straight holes vs tapered is that I can easily adjust roll center and bump steer by adding or removing spacers between the steering arm and LCA or tie rod end. Being able to adjust bump steer is really just in preparation for installing a rack and pinion in place of the stock steering box, something I have planning on doing for quite some time now. The outer tie rod is a 1/2” female heim joint with a turnbuckle that attaches it to the stock tie rod. The turnbuckle setup was used anticipating the future rack and pinion setup.

 

Reaming the steering arms.

 

 

 

[Duke]

When disassembling the front suspension to install the new LCA and T/C rods I ran into a nasty little surprise. Both of the Tokiko Illunina inserts that I had been running for the last 4 years or so were completely blown. One had lost it's gas charge and the other had a sticky rebound valve that caused about an inch of dead movement before the rebound damping engaged. I knew that my front dampers were a weak point in my suspension setup but I didn't think they would be this bad. I don't know why these failed, but I can tell you I don't think I will ever run Tokiko's again. Koni to the rescue. I went with a set of their adjustable race inserts, which should compliment the new rear shocks nicely. Then it was just a matter of getting a new set of 280zx strut housing (thanks Yenpit!) and building up a new set of shortened struts. I don't have any pictures except for this gratuitous shot of welding on the coilover sleeves.

 

[Duke]

The second autocross of the year was about a week ago and I was excited to test out the new front suspension upgrades. The car performed flawlessly. The front end handled the rough terrain of our autocross venue awesomely. There is one area of the venue that we call the “go cart” that is particularly rough. If this section is included in the course I have typically struggled. With the new shock setup the car was smooth and predictable. Even on 2 year old slicks that are getting very near the end of their life I was able to win my class end up with the 4^th fastest time of the day. I'm pretty happy with that result. Here are a few pictures from the event.

 

 

[q-tip]

Mmmmm tig welds.........

 

 

 

I wish I could use the equipment at my work, all I need is the Bridgeport and a lathe!!

[fisch]

Duke such an inspiring build. It is nice to have examples of this magnitude, even if few of us have the knowledge or means to do it, because it has the effect of everyone raising the game to their limits, and knowing we can strive to take it even further than out limits with hard work.

[Duke]

Mmmmm tig welds.........

 

 

 

I wish I could use the equipment at my work, all I need is the Bridgeport and a lathe!!

 

My dad and I added a lathe to our shop arsenal about 6 months ago and I don't know how we did anything without it!  It gets used more than pretty much any other tool in the shop now, with the exception of the welder.

 

Duke such an inspiring build. It is nice to have examples of this magnitude, even if few of us have the knowledge or means to do it, because it has the effect of everyone raising the game to their limits, and knowing we can strive to take it even further than out limits with hard work.

 

Thanks fisch!  That is one of the nicest compliments that I have gotten.  I really appreciate it.

[510T]

Hi Duke,

 

About steering arms, am I understanding correctly that the ZX arms have a larger taper than 510 arms at the balljoint?  I have a set of ZX arms I want to try on my junker but have read conflicting reports on the arms fitting 510 balljoints correctly.  I would appreciate any insight you may have. 

[q-tip]

The zx arms have the larger taper of the later 510 (70-73) ball joints, they are also shorter and offer an faster turning ratio but makes it more difficult to turn.

[510T]

Thanks Q,  The shortness I am aware of and is what I'm after.  I have later balljoints so I guess I am good to try them out!

[Duke]

Hi Duke,

 

About steering arms, am I understanding correctly that the ZX arms have a larger taper than 510 arms at the balljoint?  I have a set of ZX arms I want to try on my junker but have read conflicting reports on the arms fitting 510 balljoints correctly.  I would appreciate any insight you may have. 

Tyler, from what I understand (this is mostly second hand information, although I did put 280zx arms on a ball joint I had laying around and the following seemed to be the case) the ball joint taper on the 280zx arms is the same angle but a larger diameter.  You have to use a washer under the castle nut because the steering arm sits lower on the ball joint.  I have also heard that because it sits lower it may cause problems with the ball joint binding.  If you do end up trying them I would recommend cycling the suspension to ensure that there is no binding.

[q-tip]

I did notice that it sit further down the taper, didn't measure anything, didn't think it was that significant.