240z SCCA vintage race car, restoration

[clarkspeed]

I measured my Sweet steering shaft.  It looks like 28 collapsed and 34 extended.  And that includes the steering wheel QD spline on the end.  Like I mentioned, it is just a little on the long side .  I would say 25 to 26 collapsed would be optimum.  I also use a flat steering wheel.  If you use a dished or deep dish steering wheel, take that into account.

[AydinZ71]

1 hour ago, clarkspeed said:

I measured my Sweet steering shaft.  It looks like 28 collapsed and 34 extended.  And that includes the steering wheel QD spline on the end.  Like I mentioned, it is just a little on the long side .  I would say 25 to 26 collapsed would be optimum.  I also use a flat steering wheel.  If you use a dished or deep dish steering wheel, take that into account.

Thanks Clark! Very helpful!! Looking into columns now  

 

little update: passenger side cowl area is done. Moved over to the drivers side. Vids attached. 

[AydinZ71]

Updates: eliminated the rest of the cowl area, through to the drivers-side Pilar. Posting some pics and vids of me rebuilding the drivers side.   
 

next step is to install the tilton firewall-mounted pedal assembly. Then complete the cowl area. Steering column has been sandblasted and epoxy coated. Still on the fence on getting an aftermarket steering column. Just have not found one yet that has the features for the weight savings I was looking for. Thanks for following! 

Edited June 7, 2021 by AydinZ71

[Leon]

On 5/4/2021 at 2:35 PM, AydinZ71 said:

Update. Everything disassembled again, and bought some angle stock per Jmortensen. For the spacer, I went with 1-5/8, 0.14 wall 6061 AL. Fits pretty well (see pic). I didn’t want to go solid stock since I don’t want to flatten the natural curvature of the strut inserts bottom. Hollow also helps with concentricity. 
 

figure this is dead weight and only in compression, so why not AL. Stuff is practically free in my metal supplies discount bin. Let me know if you guys see an issue there.

 

 

 

Just keep an eye on those gland nuts. I'd suggest checking torque after each event. You should be able to easily get a wrench through the spring in order to do so. Minimal disassembly required.

[AydinZ71]

11 hours ago, Leon said:

 

Just keep an eye on those gland nuts. I'd suggest checking torque after each event. You should be able to easily get a wrench through the spring in order to do so. Minimal disassembly required.

Ah! They have a tendency to loosen up? Oh right... the expansion/contraction of the AL spacer. Yeah... that’s a good point. As the strut heats up, that AL will squish around the pressure points. I made a neoprene gasket for the gland nut/shock insert interface (seal-in oil around the insert) so that will eat up 1/32 of play. Il check the torque after I get her up and running. I bet after a few events she will seat well and stop loosening. 

[Leon]

Yup, exactly. 

[AydinZ71]

Hey guys! So I got a ton of work done this last weekend. Got the block/trans pulled, removed the whole front suspension and steering crossmember, and finished the drivers-side firewall. 
 

Question for the friends who are racing like @jhm @JMortensen @clarkspeed @gnosez @Ben280

I’m sectioning the front struts w/ GC coilovers w/ 350lb springs and Koni 8610’s + GC bolt-in camber plates. 
 

everything else is a blank page! Would love to hear your recommendations for tie-rods, co tell arms, bump-steer spacers etc. I saw a few of you modified the OEM CA’s to include heim joints and adjustable end links/turnbuckles. Wondering what worked best for you, and how you would do it if you could from scratch. Would you bother buying a product on the market?

 

Here is what was on the car (not removed since 2001). Snapped a pic of the bump-steer spacer and what looks to be a bushing offset that was pressed into the OEM bushing sleeve. I guess this moves the stock track out by an inch or so? I’d be looking to gain 2” more than stock. 

Edited June 15, 2021 by AydinZ71

[clarkspeed]

Shit gets complicated depending on diameter of your wheel/tire combo,  spring rate (wheel travel), ride height and desired roll center.. I replied somewhat on my thread. But there is a lot more involved. Tube control arms dont solve for any of those challenges. 

 

For a race car, you want to run as low as you can with no bumpsteer. There are many ways to skin that cat. I can only recommend what I have used in the past depending on your diameter.

[AydinZ71]

16 minutes ago, clarkspeed said:

Shit gets complicated depending on diameter of your wheel/tire combo,  spring rate (wheel travel), ride height and desired roll center.. I replied somewhat on my thread. But there is a lot more involved. Tube control arms dont solve for any of those challenges. 

 

For a race car, you want to run as low as you can with no bumpsteer. There are many ways to skin that cat. I can only recommend what I have used in the past depending on your diameter.

 

thanks Clark! I will be running 15X7” wheels.  Tires I had in mind were 225-50R15’s, but I am open if there is a size with larger availability. Sounds like I have to do more research. I was eyeing this book, but il take any other recommendation you may have.

 

front springs are #350lb, and ride height will likely be dictated on my final exhaust deck (as the lowest part on the car). 

 

I feel like I got a pretty good grasp on the rear suspension now that it is assembled, but admittedly I’m new to front suspension especially for a racing application. I really appreciate all your patience! 
 

Race Car Design https://www.amazon.com/dp/1137030143/ref=cm_sw_r_cp_api_glt_fabc_1VCD1Q4DQ9E1SVMX7N21

Edited June 15, 2021 by AydinZ71

[Ben280]

15x7, depending on the offset will be the limiting factor for things like the bumpsteer spacer (too thick and the tie rod will hit the wheel barrel). A quick steer knuckle can help here, since it brings the tie-rod closer to the car centerline, but for a EP/ITS car, I'm not 100% convinced you need fast knuckles. Auto-x, yes, track car, not sure. 

 

That bushing looks like a way to adjust the trackwidth/roll center without going to heims, as limited by class rules.

 

Tube arms and heims are tube arms and heims. Go with the ones that tickle your fancy and go from there. I think the Apex rear tube arms have some distinct advantages over the T3 rear tube arms, but unless you can change the inboard mount, that's gonna be your weak point IMO. 

 

Keep one eye on the rule book here, you don't want to go spending money that boots you out of the class you want to be in. 

[AydinZ71]

@Ben280 thanks Ben! I definitely have read and re-read the rule book quite a bit. The stock attachment points must be used (hence the OEM front crossmember), but methods for adjusting track/camber/caster are allowed. As long as you are not changing the attachment point itself, hence the bolt-in camber plates and using OEM subframe bolt holes. 
 

I checked with EP champ Greg Ira on this as well. He uses square tube steel for the front CA’s w/ a heim on the crossmember side. I was curious if any folks preferred the A/M parts for a particular reason, but really it’s just an arm with attachment points, as you said. Greg’s roll-center spacer is 3” tall, so il have to look into that.

 

Car already came with wheel spacers in all 4 corners. Already got rid of the rears with the help of the Apex CA’s (added an 1” to each side) I got on the used market. I would definitely prefer to get the extra track with the CA itself than live with the rotational inertia of the spacer. 
 

fun fact... I did not appreciate how fast it is to pull an engine on a race car. I went from disconnecting wires/hoses to setting the block and trans on blocks in less than an hour. Gotta love the perks of less s***! 
 

As always, thanks for all your i our folks. Really could not have gotten myself up to speed so quickly without you all. 

 

 

[jhm]

Hey Aydin, good questions all...

 

Regarding bump steer spacers:  I've been using the T3 NCRAs for several years without any issues.  I like the fact that they include both thickness and offset, which gives a wider front track.  They also help solve some interference issue between the wheels (rims) and adjustable tie rod ends, if you're using adjustables (especially with 15" wheels, although the interference may not be such an issue with 7" rim width).  I bought the T3 adjustable tie rod ends when they were only available with straight (non-tapered) rod ends....and I have to say that I'm glad I went that route.  The non-tapered rod ends have been so easy to work on vs the hassle of separating tapered tie rods every time you want to work on the front suspension.  I've stuck with 15" wheels for the lower CG height, and fortunately there are still a few good selections of tires available (for now, at least) in 15".  As @clarkspeed pointed out, your wheel size selection can dictate the rest of your design, so be mindful of that as you're making all these decisions during the build.

 

LCAs:  I used those delrin aluminum bushings for a few years without any trouble, but they became obsolete when I installed adjustable TC rods (in order to gain additional caster).  You can fab your own adjustable TC rods (several people here have threads on that topic), but I was lazy and bought a pair from Futofab.  To this day, I still think Futofab offers some of the nicest adjustable TC rods on the market.  Great design, strong materials, and a really nice price. 

 

I had to convert my stock LCAs to a monoball bushing to take advantage of the adjustability of the new TC rods, and this was an easy mod.  Just find some monoball bushings with similar outer diameter as the inner diameter of your front LCAs and weld them in (before careful when welding not to heat the inner monoball too much that it damages the teflon lining (if there is one) and ensure that your welds don't interfere with the travel of the bushing during its range of motion.  I got the idea for this from John Coffey, and have included a picture of his conversion.  I ran these monoball bushings for a couple years of hard use without any issues.  

 

After that, I decided I wanted adjustable LCAs, so I fabricated some using a pretty simple design which retains the outer portion of the stock LCA.  These are what I've been running for the last two years with no issues, and have included a pic of them.  Using off-the-shelf hardware, I think they ended up costing maybe $80 total, IIRC?  I can dig up a parts list of the hardware I chose when building these, if you're interested.  Just lemme know...

 

Spring rates:  my experience is that the stiffer springing will work well for most auto-x venues; but not so much for most road courses.  Ran 350 lb/in springs on all four corners for years, but switched to 300 last year for better compliance on corner curbing on the road courses.  I've got an adjustable front sway bar, but haven't run a rear sway bar for years. If your rules allow adjustable sway bars,  @JMortensen and @clarkspeed recently had a good discussion on that exact topic.  I've got the Koni 8610s like you have, and they've been fine.  I'll probably upgrade whenever they wear out.

 

Steering arms (knuckles):  the stock arms were waaayyy too slow for any kind of auto-x; but would probably be fine for most road racing as @Ben280 alluded to.  I got a great deal on a pair of Apex's steel quick steering arms and really like them.  They've got two mounting positions, and I've been using the "quickest" position since I put them on.  They are noticeably quicker on steering, and you really only notice the extra steering effort at extremely low speeds (like in pit lane or the paddock).  If you switch out your stock arms for aftermarket, I would highly recommend choosing steel vs aluminum and I would ensure that they incorporate the proper "twist" in their design that mimics the angle twist of the stock arms between the mounting face at the LCA end and the mounting face at the tie rod end.   

 

That's all I can think of at the moment...feel free to hit me up with any questions you may have, and good luck with the rest of your build.  It looks like it's coming together quite nicely!

Edited June 15, 2021 by jhm

[AydinZ71]

@jhm thanks again for the detailed and comprehensive response John! I just did a bunch of research on roll center on a mcphearson strut suspension geometry. I now understand the bump-steer spacer and roll-center correction spacer are in practice the same thing on an S30. I had seen those terms repeated throughout the forum, but didn’t truly understand them. I’m looking at it now and scratching my head on how Greg got a 3” spacer in there, but il grab a pic from him when his car is back. 
 

I will definitely send you a message on the part list for the LCA fab! That will help my anxiety on using an A/M LCA, knowing Greg also uses a modified OEM unit. 
 

With your recommendation on the Futofab TC rods, I’m going to go ahead and purchase. I already have a ton of stuff to fab so il take advantage of a proven existing product when I can! 

 

I’m going to use the stock steering knuckles for now, since this is an easy swap in the future. Might as well get the “feel” of the car first, and as many mentioned it’s not as necessary if turns aren’t tight. I plan on running Willow Springs since it’s only 90 minutes away, and it’s a pretty fast track. 
 

thanks again for the wealthy of info!!! Sorry all for the amateurish questions. 

[AydinZ71]

A parallel challenge! I was looking at re-mounting the steering column 100 which-ways. Nearest attachment point is the roll cage cross bar directly in front of the driver. Thinking heim joints, all sorts of complicated stuff. Then I found this product. DUH! The OEM steering column is 1.5", but it balloons to 2.38". If you remove the flanged coupling, its down to 2.25". I will wait till the driver floor pan is replaced and seat mounts are in before I settle on a final “drop” height. I wish there was an easier way make the bulkhead flange (where the column passes through the firewall) a spherical bearing other form of pivoting joint. Then I could add steering column tilt adjustment. 

 

https://www.amazon.com/2-1-Billt-column-drop-4-1/dp/B079QQNQDS/ref=sr_1_15?dchild=1&keywords=column+drop&qid=1623818944&sr=8-15

 

 

Edited June 16, 2021 by AydinZ71

[clarkspeed]

See, I told you it was a little complicated.  Especially since 1 change affects many others.  And add the fact there are multiple designs available to make the changes, and you end up with a post that is too long for me to sort out.  Mostly all good advice above.  I commend JHM for trying to put all that together!

 

 I am not going to endorse any supplier solutions since there are so many different designs out there.  I have not had any beers tonight so I will try to simplify some of this:

 

For the front suspension in my order of importance

1. A means to lower the car.  Adjustable coilovers.  Or the cheap garage solutions of cutting springs or lowering and rewelding the spring perches.  If you do these remember front and rear are different. And unless you shorten the struts, you may run out of shock travel and bottom out.  Rule of thumb is lower the car until something scrapes and then raise it back up a little.

2. Eliminating bump steer=high priority and needed on all race Z's. You are trying to make the control arm and tie rod operate in parallel.  Must be estimated to be adjusted and there are some easy/cheap ways to do this.  I use plywood on a piano hinge with 2 screws that touch the wheel.  I adjust until no gap. Or you actually measure it with a nice tool and dial indicators.  May be accomplished by spacers at the tie rod end or slotting/enlarging the inner control arm pivot hole in the cross member.  It does not take much on either end, maybe 3/16" max and usually less. Slotting not legal in most classes, but an offset bearing is another option. Perhaps a bigger hole or smaller bolt? Tie rods with rod ends can be purchased and you can straight drill through steering knuckle.  Or you can build one yourself by cutting off the end of a stock inner tie rod and welding it into some tubing. Thread adapter on the other end for the rod end.  I prefer using Pinto bumpsteer kits with a tapered bolt rather than drilling out the knuckle.  Be careful the bolt/spacers do not hit the wheel.

3. Roll center is important but not important.  Most conventional setups will try to keep the RC just above ground which means the control arms are slightly pointed down toward the wheel. I posted a roll center calculator in the forum somewhere and it is accurate. But running the roll center below ground is also possible.  I think the general rule is not letting the RC move through the ground plane during operation. And never run a high roll center (more than 4"), it puts much of the loading back into the chassis which is not a fast recipe. Roll center location is very dependent on wheel/tire diameter and lowering the car.  There are a couple ways to move the roll center. Different wheel/tire and ride height as mentioned above.  Also again slotting the cross member to raise inner control arm hole. A more common solution is to add a spacer between the ball joint/steering knuckle and strut body. There are various lengths available including offset ones.  And you can weld 2 together for a longer solution.  On the tube car I am building I put a bolt here and will use spacers similar to a bump steer kit combined with a spherical bearing as my ball joint.  Either way, to change the control arm angle you either must relocate the inner pivot or the ball joint in relation to the chassis.

4. You will want to run as much track width as possible but will be limited by rules or fenders or geometry. Rear track does not need to equal front.  More track with in front is a good thing. Longer or adjustable control arms or wheel spacers can work here.

5. Normally a means to adjust the camber is needed.  Many solutions here also.  If you lower the car just right and run bias ply tires, you can get away with nothing.  Otherwise, depending on spring rates, you probably need between 0.5 and 3.5 degrees of camber adjustment.  Bias tires 0.5-1.5 and radials 1.5 to 3.5.  Softer the spring, more camber usually required to get a good tire contact patch under full G load. Camber can be adjusted by moving the upper strut bearing (camber plate) or extending the control arm.

6. A different solution for the T/C rod.  Rubber bushings are not acceptable for road racing.  They will make your butt tighten up on heavy braking.  Poly is almost acceptable but still wallows a little under heavy braking and has lots of sticktion.  The Delrin ball aluminum cup works well but the Delrin doesn't last long and will really scare you (and drivers near you!) under braking when it cracks up.  A common solution is replacing the joint with a rod end.  But most of these involve bolting a clevis into the pocket which moves the pivot point slightly outboard.  I never liked that but it is better than nothing and you can add couple degrees of caster at the expense of pushing the wheel forward in the wheel well. Seems like I saw some vendor did this correctly but I can't remember which one. More caster is good, but if you push the limits and add lots of caster here be very careful of interference.

7. Weight.  There are some cool control arm designs out there.  Some of them weigh many pounds more than stock. I always ask myself, if the stock stamp steel stuff is plenty strong to race with, why do I need extra thick wall tubing to replace it with?  It is not good to add 5 more lbs of unsprung weight. Some of the more popular vendors use very heavy designs because they are designing for street cars and extra safety.  That's when building your own starts to look attractive. 

8. Eliminating friction or "sticktion".  Replacing the stock control arm inner bearing with a spherical bearing or purchase of a control arm with rod ends.   

9. Steering knuckle - driver preference, some road racers shorten but not that many.  Many autox'ers do but not all.

That's all I can think of for now.

 

[AydinZ71]

@clarkspeed Thanks for the incredibly comprehensive response Clark!!

 

1) 100%. Have GC coilovers at each corner w/ GC bolt-in camber plates (to maintain EP spec). Will adjust ride height after the exhaust is in. 

 

2 & 3) You have given me a lot to think about here. Car came with 3/4"" spacers, so I'll have to measure and possible buy more or taller spacers once I have the ride height set. Greg runs 3 1" spacers stacked, and has one machined to make-up for the effect on camber/angle of the LCA mounting surface. 

 

4) 10-4! I am allowed 2" extra track total (1" on each side). I will achieve this by: a) modifying stock LCA w/ heim rod-end w/part list recommended by John. b) Futofab TC (on order) c) either Apex s130 front "low profile" tie rod kit, or fabricate my own with parts from McMaster. All three parts will work together to achieve the +2" plus track I need. 

 

5) I am running #350 springs in the front. Il be able to add the negative camber w/ the camber plate, and the addition of track. I am targeting -2 degrees, but might go less as you suggested for the heavy springs. 

 

6) The Futofab TC's should solve this concern, but Il look at it more clearly when they are in-hand. I need to become more familair with the geometry. 

 

7 & 8 ) agreed! Will be looking into heim rod ends for sure, regardless of something I fab or purchase. It is frustrating that the A/M suppliers done explicitly state the weight. Not sure why... I weigh every OEM suspension part I remove from the car so I can keep track of the net +-. 

 

9) yeah I will use the stock knuckles for now

 

With all of your help, I have a much much better grasp on the front suspension geometry and modifications. Il have to play around with the roll center a bit, but besides that I think I have it squared away! Thank you again for your help Clark, Ben, John!

[clarkspeed]

5. 350 is not super heavy but probably a good place start. I forgot to mention grip level affects camber also. You will have a lot more body roll with super grippy EP cantilever slicks than with a 200TW street tire for example. Make sure you can get to 3 degrees, you may need it.

 

6. Yes the Futofab TC's look decent but I have never run them. I had some TTT TC's on another and they were solid for sure, and heavy as hell.

[tube80z]

On 6/14/2021 at 8:22 PM, AydinZ71 said:

 

thanks Clark! I will be running 15X7” wheels.  Tires I had in mind were 225-50R15’s, but I am open if there is a size with larger availability. Sounds like I have to do more research. I was eyeing this book, but il take any other recommendation you may have.

 

Race Car Design https://www.amazon.com/dp/1137030143/ref=cm_sw_r_cp_api_glt_fabc_1VCD1Q4DQ9E1SVMX7N21

 

What are you looking for in this book?  I have and have only went through it one time and now another.  The author seems to either be an academic or someone who has no real experience with racing cars.  Almost all the examples are trivial to explain some vehicle dynamics concept with a nice easy to solve formula.  

 

I think if you're totally new to FSAE this may be okay as a starter but even then I have a lot of reservations.  The author often throws out some rule of thumb or says this would make a nice starting point.  In FSAE you better have the knowledge of why and not say rule of thumb, etc.  Where this book is okay is showing all the bits that go into a car and some of the basics you need to think about.  

 

When it comes to the most important chapters (testing) it's very thin on commentary and gives no guidance on keeping records, what's most important to do first, etc.  One thing Claude Rouelle harps on is when you win or the car is working really well you need to understand why.  This is the only way you can ever get it back into this window when it drops out.

 

My opinion is that I don't think there's any one book that covers it all very well.  For the era the Z was designed in two books stand out for me although they are feeling long in the tooth now.  Those Racing and sports car design (Costin and Phips), the Race and Rally Car source book by Staniforth, Think Fast (Neil Roberts), and the Carrol Smith to Win series (at least get prepare to win).  And then things get hot and heavy on my bookshelf.  So it really depends on how far you want to take some of this stuff.

 

Hope this helps,

Cary

[AydinZ71]

@tube80z

 

hey that’s super helpful! Thank you! It’s tough to find the “right” book. I’m just looking for a general book on race car chassis and suspension dynamics based on empirical data more than theory. I have an engineering background so I got the theory part covered. Il definitely take the suggestions you provided! Doesn’t look like the book I found is right for me.

 

thanks again for your help! 

[AydinZ71]

I got one LCA modified. It looks like a phallic spaceship. Thanks again for everyone’s help on this!