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240z SCCA vintage race car, restoration


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On 5/3/2021 at 8:55 PM, JMortensen said:

The rear strut tube should be 2" longer than the front, and yes, you need a spacer under the strut if you are running the same insert front and rear.

Because you lose an inch more in the rear on a 280 by removing the taller isolators, and the front is the end that runs out of travel, you really don't need to section 280 struts in the rear at all. 

If you dig enough you might come across some posts from me from about 10 years ago when a guy had sectioned his rear struts and was trying to run it anyway. He had preloaded the crap out of the springs trying to get the ride height higher and that just meant that the suspension kept topping out. He spun A LOT that day. A LOT. LOL

 

Hey Jim, et al.

 

I am about to section my front struts and want to get this right. Do you, or anyone else know if I need to add 2" to the strut tube in the front as well? The dimension provided by GC from the bottom of the tube to the new coilover lower perch is 5" (rear was 7"). 

 

Also, if I add length to the front strut as well and use a spacer in the tube like I did in the back, doesn't this also act similar to the bump-steer/RC spacer? 


PS: I think I answered my own question: NO. Making the strut longer still moves the wheel hub lower. In order to correct RC, you need to increase the vertical gap between the wheel hub and the LCA, giving the arm a greater angle. 
 

 

-Aydin 

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thanks! Gosh I’m not sure how to adjust the res of the photo’s uploaded here. I can try e-mailing them to myself and uploaded from a computer instead of from my phone. The pictures themselves are huge

Hi all!   Restoring a rusted 240z series 1, SCCA vintage race car. Car last raced in 02'. Currently rebuilding to group EP spec's. I figured id start a new thread summarize my plans and prog

That is where it should go. Everyone usually mounts the cell at deck height which never made sense to me. Then you have to separate it from passenger with a big ass box or bulkhead design. Drop it dow

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It's Jon, but everyone does that. ;)

You don't need a spacer in front. Adding one doesn't change geometry, it will just reduce available bump travel, and gaining some travel is really the main point of sectioning struts. 

You will need a spacer in back. The rear strut housing should be 2" longer than front on a 240, 3" on a 280. If you don't have a spacer in back, the suspension will be really extended as compared to the front. If the rear tops out too much you'll get a loss of traction.

The hub is below the strut tube, so adding length to it doesn't change the roll center. If you want the roll center higher then you have to raise the inner pivot of the LCA, or lower it on the outboard end, or both.

You will then need to fix the bumpsteer, as changing just the LCA angle will screw up bumpsteer. To change the bumpsteer you can raise the rack or lower the outer tie rod, or both.

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48 minutes ago, JMortensen said:

It's Jon, but everyone does that. ;)

You don't need a spacer in front. Adding one doesn't change geometry, it will just reduce available bump travel, and gaining some travel is really the main point of sectioning struts. 

You will need a spacer in back. The rear strut housing should be 2" longer than front on a 240, 3" on a 280. If you don't have a spacer in back, the suspension will be really extended as compared to the front. If the rear tops out too much you'll get a loss of traction.

The hub is below the strut tube, so adding length to it doesn't change the roll center. If you want the roll center higher then you have to raise the inner pivot of the LCA, or lower it on the outboard end, or both.

You will then need to fix the bumpsteer, as changing just the LCA angle will screw up bumpsteer. To change the bumpsteer you can raise the rack or lower the outer tie rod, or both.


thanks Jon! Super helpful :) apologize on goofing your name! In hindsight I have addressed you as Jon already so not sure what I was thinking. Il look for holes in my welding mask 😂

 

I got the rear’s fixed by re-sectioning them and adding the length. You were super helpful on that! 
 

on the fronts, looks like il just be making sure the coilover sleeve does not extend above the gland nut. Got it! 
 

any suggestions in an adjustable outer tie rod? I fabricated my own LCA’s (thanks @jhm) (previous post) and have purchased the Futofab adjustable TC rods. I’m on the fence on the outer tire rod. Either going with apex (not bad for $215), or fabricating my own with a left/right thread coupling nut or double-adjuster rod. 

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I drilled the knuckles out to 5/8 and used a bolt. Originally I was planning on using the stock rack and so I  made my own tie rods by cutting the ends off of a stock set and welding them to a swaged 5/8 steel circle track tie rod. Wasn't hard. If you do this just order a really long one and cut in half and use the LH threaded side with the RH threaded stock end and vice versa. 

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Forgot to mention, the problem you run into with adjustable LCAs is running out of threads on the tie rods. If you go to a turnbuckle style you can make it a little longer to start with and then you're length adjustments are split between both sides, instead of all the adjustment happening on the inside as it works stock. 

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On 6/24/2021 at 3:53 PM, tube80z said:

 

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

100% agree books are not going to help much if you already understand the concepts. My shelf is also heavy, I think I have the Costin book but not the Rally one from Roberts. My fallback has always been Puhn's How to Make Your Car Handle. It's an old one but i think it covers the basics well. 

Tuning a race car is not covered in any books that I know of. Someone will probably write it eventually or even post videos, but for now it is reserved for seminars and consulting (some online!). 

My advice is keep doing what you are doing. You have not gone off the tracks yet.

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On 7/2/2021 at 7:04 PM, clarkspeed said:

100% agree books are not going to help much if you already understand the concepts. My shelf is also heavy, I think I have the Costin book but not the Rally one from Roberts. My fallback has always been Puhn's How to Make Your Car Handle. It's an old one but i think it covers the basics well. 

Tuning a race car is not covered in any books that I know of. Someone will probably write it eventually or even post videos, but for now it is reserved for seminars and consulting (some online!). 

My advice is keep doing what you are doing. You have not gone off the tracks yet.


appreciate it Clark! Il try some YouTube vids. Greg has been super gracious to help, but I don’t want to bury him with questions I can have answered elsewhere. 
 

in other news, look what I just got in the mail. Surprise! This assembly has got to be less than 8lbs. 

5666F175-6918-4B4F-A6A5-DBE46FBD7B15.jpeg

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On 7/2/2021 at 7:04 PM, clarkspeed said:

My fallback has always been Puhn's How to Make Your Car Handle. It's an old one but i think it covers the basics well. 

Plus you can see my ex-boss from the Porsche shop I worked at 20+ years ago in there. Well, his hand, anyway. "Guy Ober squares the suspension on his race Pinto using a plumb bob." Something like that. LOL

Best thing I've seen on tuning race cars in a long while was about running sweeps. By sweeps I mean go too far one direction all the way to too far in the other direction, then find your happy setting. When I first started racing in the mid 90s, my roommate was a Nissan master tech who had been autocrossing for years. Among his pearls of wisdom were: "Never go bigger than a mild cam on an L series, because you'll lose bottom end" and "run about 1.5 degrees negative camber in the front, slightly more in the rear" and "V8s are too heavy and a Z won't turn with one." He had learned these rules from somewhere and parroted them exactly. I listened to him because I didn't know any better and he was the expert. Then Carl Beck's Z car email list started up and I got on it and people were running big cams and had V8 autocross cars with 3+ degrees of camber. He said: "You don't know who you're listening to when you get advice on the internet." That's true, at the time I didn't know John Coffey, Pete Paraska, Gary Savage, etc at the time, but man, were they right and he was wrong. Great to find out we were doing it wrong, but doing sweeps would have told me that without having to run into the right people.

Start with too little camber. Go run it. Keep adding neg camber until the inside is obviously too hot, then back it off to where it makes the tires happiest. If I had done that I would have found the answers years earlier and been a lot faster. A quick way to shorten this whole idea up would be to say: "If you haven't gone too far, you may not have gone far enough." 

BTW that button clutch is hawt. I love my dual 7.25". Not very streetable, but man does my T56 shift fast with one.

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Jon, you just gave away every race engineer's secret! Just kidding, but that is where every great set up starts. Once your setup is in the ball park, test sweep the tire pressures and sweep the camber. Make large changes so you have an obvious change. Data collection helps if you are not a consistent driver. Maximizing the grip of the tire pays huge dividends. When a pro team buys a new car, they go to the track to test and run sweeps.

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@JMortensen @clarkspeed Thanks guys! everything you say makes sense. Basically, figure out your extreme thresholds, and work your way into a "sweet spot". It clearly will not be near the extremes, but you don't know if it will be 60/40% until you work your way to the center. Thanks for the advice!!

 

That should get my camber, and tire pressure dialed in. Il have to do more research on setting my roll-center. I am certainly not a consistent driver, so the tuning will improve as my driving improves as well. 

 

Yeah I told Greg i was looking at steel 10lbs unit. He was like "HA!, I just saved you 20 seconds on your lap time." I got the auto-trans flex-plate and spacer too, but still working on the chassis until I get this thrown on... 

 

Also, I am settling on the Apex tie rods (steering). Its the last suspension part I need. I lied...I still need to dial in RC, but those are just spacers. I have a 1" front sway bar and plan to run none in the rear. We'll see how it goes! 

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On 7/2/2021 at 7:04 PM, clarkspeed said:

 My fallback has always been Puhn's How to Make Your Car Handle. It's an old one but i think it covers the basics well. 

 

 

Holy Crap.  Time warp.  I read that book in high school in the (I don't even wanna say what decade) when I first became interested in cars.  You jogged something in the back of my mind, otherwise I had forgotten it even existed.

 

I vaguely remember racing cars with drum brakes, things like that in the book.

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Ha, not sure that clutch saves 20 seconds, but it does help.  Roll center not super critical. Just like most settings, you want to know where it is, and where it goes after you make changes because it influences what you feel on track. Again if you follow the advise you have so far you will be in the ball park.  

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54 minutes ago, Ironhead said:

 

Holy Crap.  Time warp.  I read that book in high school in the (I don't even wanna say what decade) when I first became interested in cars.  You jogged something in the back of my mind, otherwise I had forgotten it even existed.

 

I vaguely remember racing cars with drum brakes, things like that in the book.

Honestly, I think it might have been the first race/setup book I ever bought, but I have yet to see anyone cover the basics as well.  And yes there are some really funny old pictures in there, like 8 degrees camber or something.  I think it has been revised a few times by now.  

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  • 2 weeks later...

More progress. Getting there! Starting to finally see the light at the end of the tunnel. Floor pan is ready for the seat mount crossmembers, then I can mock-up the tilton pedal assembly. I also ordered the Stahl style header from ACP per Greg’s recommendation. Also have all the front suspension components in hand.

 

 

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17 minutes ago, clarkspeed said:

Looking good. Man that is a lot of welding. I don't see any holes in the firewall for the brake clutch MC's? 


thanks! 
yeah man… it’s a frickin jigsaw puzzle, LOL 😂

 

Just finishing up a few structural pieces before I mock-up the Tilton pedal assembly. OEM holes were not going to work, so I just started with fresh steel. 

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@jhm thank you, sir!

 

Update: ACP in Penn. is making me a Stahl style header. Greg was keen on not skimping on this part. Also got me an ATI damper and all parts for the front suspension are in hand:

- Apex s130 low-profile adjustable tie-rods (steering). Starts at 3/4”+ track on S30
- John’s OEM LCA mod with adjustable track 

- Futofab TC rods

- GC coilover w/sectioned OEM struts. GC bolt-on camber plates

- Koni 8610’s

 

questions:

 

1) anyone run a racing/lightweight alternator? Greg uses Li batteries w/o alt., and just charges the batteries after the race. I don’t think I’m there yet, so looking for a compromise. I found this. Eager for your feedback! 


2) looking into AIM dash loggers. Anyone run these or have any preferences?

 

 

PS: mocking up the pedal assembly 

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Edited by AydinZ71
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