AME complete chassis '77 280Z

[lifeprojectZ]

10 hours ago, clarkspeed said:

First I have seen this thread. Very ambitious. Good luck and glad to see you finally got back to your dream car.

Thank you.   After 21 years of sitting on it, I finally decided to make a (major) move.   Now there is no looking back.   I am committed and need to have this on the road within a few years.

[lifeprojectZ]

11 hours ago, A to Z said:

Sounds good, but PICTURES are priceless.

 

I don't have a whole lot to show at this time until the wheels arrive (later June) and the chassis (hopefully September).    I finally removed the ugly rear bumper gap cover by drilling out the spot welds.  I managed to only completely perforate the body once in the process.    Steering rack simulator linkage below.  Tubes cut to length, I just need to prep and weld in the threaded tube ends.   This will be my first real welding project with my Miller 200DX which I bought 9 years ago (for the Datsun).   I am a novice welder, having TIG welded some tubing back in the 1994 timeframe, and only about 5 minutes of TIG welding since that time with my inverter TIG.   The outer links are 7/8" OD tubing, chosen to match the link tubes O.D. that are coming from AME, because one of the other things I need to check is that at full track travel, they don't interfere with the front sway bar links.    AME already drop shipped the Wilwood front brake kit (12.88" rotors, aluminum hubs, 6 piston calipers) at my request, so that I could get the hubs ready to mount on the spindles when I have the chassis in my driveway.   The chassis comes assembled in the crate.    I have to be able to mount the wheels to roll it into my garage.   No forklift at home!

 

Wilwood BP-10 pads included.   Anyone know if they are any good or not?

 

 

[A to Z]

Ah, cool!  thanks for sharing!

 

[jhm]

On 6/4/2022 at 11:51 AM, lifeprojectZ said:

Wilwood BP-10 pads included.   Anyone know if they are any good or not?

 

Yes, they are quite good IME.  I run both the BP10 and BP20 compounds, and even the softer BP10 are quite adequate for 30-minute heats at the track.

[clarkspeed]

With those giant rotors, you will not generate very much heat into the pad (relative of course). The Wilwood pads are surprisingly excellent for that application in street or track duty. 

[lifeprojectZ]

I’ll have a Fat Tire please.

My wheels and tires arrived this past week.   Here are the specs:

 

Front:  Forgeline GA3 18x9 with 5.5” backspacing.  5 x 4.75” bolt pattern.  Michellin PS4 255/35ZR18

Rear:  Forgeline GA3 18x10.5 with 7” backspacing.  5 x 4.75” bolt pattern.  Michellin PS4 295/30ZR18

 

I spent no less than 20 years thinking about tires and wheels for my car.  For a long time I was leaning toward 17” wheels and thought that this size looked the best aesthetically.  But once I started designing the custom chassis earlier this year, I had to finalize the decision.  So I looked for every photo I could find online of tire/wheel sizes for a Z car, and also examined tire sizes online to see what was commonly available and the price tag thinking about replacements in the future.  I considered square setups and staggered setups with different tire sizes front / rear.

 

I decided early on that I wanted to keep overall tire diameter in front and rear as close as possible to OE, for handling, balance, and overall packaging concerns.   OE tire dia. is about 24.6”.  A lot of tires being used on these cars, like the 275/40R17 look too large on the car for my liking.  That tire is a full 1” larger in diameter than OE.  So for a good while I thought I would go with 255/40R17 on all four corners, at 25” diameter.   As I thought more about this and came closer to the time I needed to lock down the decision, I moved in favor of the larger 18” setup, primarily to get more grab in the rear with the availability of a wider tire – the 295/30R18 – at the same diameter as the narrower 255/35 – 25” in diameter both.

 

As for the wheel width and backspacing, I worked from the outside in of the car.   That is, I measured the total width of my car body between the widest points of the fender lips.   I came up with about 63.5” both front and rear.   I wanted to keep my tires inboard as much as possible, because I think some of the set-ups I see look a bit too much like a VW beetle, with the tires well outside of the natural body lines of the car, with extra wide fender flares starting to approach beetle likeness.   This is more noticeable viewing these cars from the front and rear.  Not so much from the sides.

 

So I designed around a “bulge width”, of 64.5”, for both front and rear.   That is, from the outside bulge of the left tire to the outside bulge of the right tire.   This gives me approximately ½” of tire bulge outside of the OE fender lip at its widest point.  (So I will still need fender flares, but less aggressive than most setups with OE rear suspension and wide tires)  This setup gives me quite a bit more tire width on the inboard side compared to OE tires, without causing interference with steering, suspension, or frame.

 

Initially I was considering 65.5”bulge width in the rear and 64.5” in the front, but the president at AME voiced the opinion that my car was going to tend to plow, and I would have to power around curves, so I decided on my own to bring in the rear tires another ½” on each side to equal out the front, thinking that this would counter the tendency to plow.  (Hope it does)  Of course doing this at the sacrifice of reducing space behind the tires and rear suspension for exhaust and fuel tank mounting.

 

On the rim widths, I went with the measured rim width as listed on Tirerack for the tires I choose, thinking that this would give me the best overall performance.  I am happy with the aesthetics, although the front tires do look slightly more stretched on the 9” wide rims than the rear tires on the 10.5” rims.  The difference is subtle though.

 

Deciding on Forgeline wheels came relatively late.   I hadn’t even heard of Forgeline until earlier this year.  I was looking at Boze Forged wheels after seeing these on one of the higher profile Z cars visible in photo shoots on the internet, and I called Boze several times and spoke with the owner and his son.   They were nice people, but ultimately I didn’t like that they only perform final assembly/ machining, and couldn’t give me very detailed information up front about their product.  They buy their center sections and rims forged by another company in the US.   Their web site shows absolutely no infrastructure / machining operations, so I felt that I would be better off looking at some other wheel companies.

 

I looked at Billet Specialties and called them.   The guy I spoke with came across a little arrogant when responding to my questions, and not very interested in my project.  So I ditched them immediately.

 

I came across a video on Youtube in which the owner spoke highly of Forgeline wheels, so I decided to check them out.    Their website and videos impressed me that this is a serious wheel company, so I looked for a dealer and came across Hawk’s Motorsports just 45 minutes away from me.   The Forgeline website is probably one of the best I have seen of any wheel company, giving specs, pricing, and photos of their wheels used on customer cars.   They list retail pricing, but a sizeable discount is available when buying through a dealer.  The wheels are made in Dayton, Ohio.

 

I am happy with the service from both Forgeline and Hawk’s Motorsports where I bought the wheels/tires.  Nice people at both places, and I can recommend both.  I had a nice exchange back and forth with the owner and president of Hawk’s.  He has been very concerned to make sure I was satisfied.

 

Now I have to find a closet to hide these until the chassis arrives.

[lifeprojectZ]

Tough nuts.

 

Not much Datsun progress in the last few months.  Just a lot of worrying about how the steering rack and engine mounting will come together in the new chassis, and clearance for even custom headers with the new upper control arm mounts on the frame rails.   ....Had to get lug nuts to mount the wheels to the chassis once I unload it in the driveway, so I bought Mcgard tough nuts, having some good experience with them in the past.   I also decided to upgrade the front wheel hub studs from the Wilwood kit (black oxide) to ARP studs which are cadmium plated.   I haven't had any good experience with anything black oxide coated not rusting and causing grief eventually, so I didn't really like the idea of using them.  

 

Yesterday I called Art Morrison and discovered my frame has been completely welded and was quality checked that morning.   So after paying off the balance next week, they will mount the F/R suspensions and I am supposed to take delivery about mid-September, which is right on the 6 month window they quoted me back in March, so I am quite happy with that.

 

This summer was extremely hot and humid in S. Carolina, and with temps in the upper 80's in my garage I haven't felt like welding too much, so I still need to finish my steering rack simulator, photo below, which I designed with DOM tubing, threaded tube ends, rod ends, and two birdcage clevises.   Nominally the rack length (pivot to pivot) is 21.5" which was what AME specified, but I made it such that I can shrink that pivot distance if needed to improve bump steer.  My plan is to play with the mounting position and pivot-to-pivot length to dial in both bump steer and Ackermann geometry before ordering the Woodward rack.

 

I ran into what could be an issue with the rear wheels.  The pilot bores are 2.768", and the pilot stubs on the rear wheel hubs are 2.760".  When I gave the specs to the dealer to order the wheels, I gave the 2.76" dimension, but it seems to me like someone either misunderstood this or didn't leave enough clearance.   I wrote back to Forgeline, and the sales rep confirmed to me that for a pilot stub dia. of 2.76" they would have machined the bore to 2.78".   That seems more reasonable to me.   So now I am thinking about using a ridge reamer to open up these bores.   Any thoughts / comments / experiences appreciated.   I am thinking it will be difficult to mount wheels with only .004" radial clearance in the pilot, and over time the aluminum may seize to the steel hubs.   But maybe I am overthinking things.

[clarkspeed]

Hopefully i understand the question correctly.

I think you will be fine. The wheels should be self centering with tapered lugs so they only need enough clearance in the middle. It is more important that rear rotor hats (if running them) have a nice spigot fit over the hub centers. Just like the stock drums do.

Which is next question, what are you running for rear brakes? Depending on what you slide over the rear hub, you wheel interference may go away.

 

And Forgeline is A1 Top Notch wheel. 

 

[lifeprojectZ]

On 8/23/2022 at 4:50 PM, clarkspeed said:

Which is next question, what are you running for rear brakes? Depending on what you slide over the rear hub, you wheel interference may go away.

 

For the rear brakes I ended up going with the 2010-2015 Camaro standard rear brake setup with OEM cast iron rotors (12.4") with parking brake hub and floating single piston calipers.  (The knuckles are OE from the 2010-2015 Camaro).    This was really the only option that matched the front brake setup with the 12.88 rotors / 6 piston calipers.   Apparently these rotors have a center pilot hole machind out to 2.783" to ride over a diameter of 2.780 on the wheel hub pilot shoulder which for some reason they are using from a C6 Corvette.  This is slightly larger in diameter than the nose of the pilot which goes into the wheel center hole, which AME told me is 2.760.   

 

I spoke with sales guy at Art Morrison again today, and the chassis is supposed to be ready to ship in 1-3 weeks now, so time to start clearing space in the garage!

[clarkspeed]

Sorry I did misread your post (with history).

 

I would assume the wheels are still lug centric.

[lifeprojectZ]

On 8/26/2022 at 11:50 PM, clarkspeed said:

I would assume the wheels are still lug centric.

 

I'm still confused on this myself.   There is at least one youtube video from Forgeline in which they say that their wheels are hub centric, and I take that to mean they are centered on the pilot bore.   I wouldn't think you would want to do that with conical lug seats which will naturally seat the wheel when the lugs are tightened.   Really, the lug hole circle in the wheel should be "perfectly" concentric with the pilot bore if the wheel was machined correctly, so I guess it shouldn't matter.    My Toyota vehicles use straight shank style lug nuts with flat washers, so I am guessing they are centered off the pilot.   I may yank one of those off to check pilot bore and hub pilot dia. just for curiosity sake to see what the design clearance is.

 

After some very brief TIG practice and a lot of reading and watching videos, I started to weld the threaded tube ends on the steering rack simulator adjuster sleeves.   The photo attached was with no filler rod and went pretty smooth.   On the other end the tube end is thicker and I am having more trouble blowing out the thinner tube metal from the puddle, so today I will try running up the amperage a little, adjusting arc focus on the thicker material, and adding filler to see if I can get those to come together.    I am a welding novice, and will have to get significantly better before I do any welding that counts! 

[clarkspeed]

Hub centric most likely means then bored the hub true to the lug/wheel diameter. Sometimes custom wheel manufacturers don't take the time to do this. Without the true hub, you need an adapter that bolts up to do the spin balance.

[lifeprojectZ]

Chassis on the way and first problem with Wilwood parts.

 

The chassis shipped out from Art Morrison on Thursday and tentative delivery is next Thursday, so I am getting ready to receive it, transport home and uncrate in the driveway.   I'm building the front hub/rotor assemblies now, and ran into my first problem with the Wilwood parts.   The little 1/4-20 countersink screws that hold the rotor hats to the wheel hubs protrude from the rotor hat by about 0.005".   Even torqued to spec, they do not sit flush or below surface, so these would create a stand off from the wheel hub mating flush with the hat.  Very frustrating.  I thought for a few minutes about calling Wilwood over this, but I can only imagine the circus that would ensue.  Temporarily, I took two screws and sanded down the flat heads to remove just enough material so they sit below the rotor hat surface, one for each hub.   These screws look cheap and have what looks like a hot galvanized coating.   The Wilwood package says they are zinc plated, but they aren't shiny and don't look like normal zinc plated fasteners.   I found the same screws in 304 stainless on www.boltdepot.com, so I am going to get some replacements coming and have a friend machine down the heads slightly so they don't protrude and cause problems with wheel mounting.  

 

I started to torque the screw-in wheel studs into the backside of the wheel hubs, and got very nervous about stripping threads.   Spec is 77 ft-lbs, and it just felt like the studs were turning too much after making contact, so I stopped at 50 ft-lbs.   I might call Wilwood about this.    Anyone reading have any similar experience torqueing into aluminum threads?   The studs are 1/2-20.   

[clarkspeed]

Man, you are on your own for this build. But it sounds like you have the capabilities to work through it. The CSK screw solution is fine. You can probably find a good torque number for steel into aluminum on Google. Trust your instincts, they seem fine.

[lifeprojectZ]

2 hours ago, clarkspeed said:

Man, you are on your own for this build. 

 

Ouch, I hope not!   I want to get thoughts, opinions and questions through sharing my progress, as I know that will make me consider my steps more carefully and ultimately make the project better.   I can think through many things on my own, but the experience of those here who have already modified their Z's and raced them is invaluable to me.  I've done a lot of reading and research over the years including on this site, but have put off the doing until now....   Thanks for your comments.   More to come...

[Dat73z]

77ft lbs into aluminum doesn't sound right for a 1/2 sae fastener. 

 

I took a quick look online and found this for 6061 T6: 

 

https://www.wermac.org/bolts/bolts_bolting-torque-tables_stud-bolts_flange-bolt-up_table4.html

 

I would call Wilwood and ask. I used to be an ME and had lots of books around this. I'm sure if you searched around, you'd find the table for your material. 

 

Here's another for 2024 t4: https://www.engineersedge.com/torque_table_sae.htm

 

For something as critical as brakes call the OEM. 

Edited September 10, 2022 by Dat73z

[lifeprojectZ]

1 hour ago, Dat73z said:

77ft lbs into aluminum doesn't sound right for a 1/2 sae fastener. 

 

I took a quick look online and found this for 6061 T6: 

 

https://www.wermac.org/bolts/bolts_bolting-torque-tables_stud-bolts_flange-bolt-up_table4.html

 

I would call Wilwood and ask. I used to be an ME and had lots of books around this. I'm sure if you searched around, you'd find the table for your material. 

 

Here's another for 2024 t4: https://www.engineersedge.com/torque_table_sae.htm

 

For something as critical as brakes call the OEM. 

 

The OEM's (Wilwood) instruction sheet for assembling these hubs specifically states to torque the studs to 77 ft-lbs, and I have found other similar specs published for aluminum female threads with 1/2-20 grade 8 bolts (the wheel studs are actually stronger than grade 8).  My feel on the torque wrench today is what gave me pause to stop and challenge this and ask for others' experience.   I am a PE and capable of calculating the average stress on the aluminum threads assuming a value for the constant used in the calculations.   Admittedly I haven't done that yet - LAZY!   However I also remember from engineering school (strange I remember anything) that the stress in reality is greater in the entrance threads because the bolt stretches as you tighten it.    So even the best calculations may not align with test data / real life.   I can just imagine Wilwood's response to me calling over this, as I already called their tech line previously about another matter and found them useless in that instance.   I will do it nonetheless and see what they have to say.  I might be worried over nothing.

[Dat73z]

22 minutes ago, lifeprojectZ said:

 

The OEM's (Wilwood) instruction sheet for assembling these hubs specifically states to torque the studs to 77 ft-lbs, and I have found other similar specs published for aluminum female threads with 1/2-20 grade 8 bolts (the wheel studs are actually stronger than grade 8).  My feel on the torque wrench today is what gave me pause to stop and challenge this and ask for others' experience.   I am a PE and capable of calculating the average stress on the aluminum threads assuming a value for the constant used in the calculations.   Admittedly I haven't done that yet - LAZY!   However I also remember from engineering school (strange I remember anything) that the stress in reality is greater in the entrance threads because the bolt stretches as you tighten it.    So even the best calculations may not align with test data / real life.   I can just imagine Wilwood's response to me calling over this, as I already called their tech line previously about another matter and found them useless in that instance.   I will do it nonetheless and see what they have to say.  I might be worried over nothing.

 

Maybe ask to speak to another engineer. 

 

Do you have a picture of what you're torquing into? For some reason I'm thinking the floating hub adaptor for the rotor but perhaps I have the wrong idea. 

 

I ask because for steel into AL which is constantly heat cycling through the extremes, I always use some form of anti seize to prevent thread galling but that can also change the torque spec. 

 

One thing you may also want to consider is drilling and safety wiring all brake and hub hardware. It's a bit more incremental effort on the frontend, but worth it for peace of mind. 

[lifeprojectZ]

Pictures attached.   They are the wheel lug studs that thread into the Wilwood aluminum hubs.   These studs just thread in through the back side instead of being pressed in with splines.   

[lifeprojectZ]

1 hour ago, Dat73z said:

 

Maybe ask to speak to another engineer. 

 

So I opened my Shigley and Mischke Mechanical Engineering Design and also my (preferred) Mechanical Engineering Reference Manual for the PE Exam.   My quest is to get a better idea of what it would take to strip out the threads and if I would be close at the recommended torque.    Easy formula:   Preload = Torque / (K * Bolt Dia.).   Getting the right K factor is the challenge.   The K factor table in the Shigley and Mischke has black oxide at .3 and cadmium plated at .16, but I know that these may not be accurate for aluminum threads, as K factor is calculated from a more complicated formula with actual coefficients of friction.   Nevertheless, I ran the following calcs which leave me 50% confident I didn't already screw up the aluminum threads, no pun intended.    Next step will be to contact Wilwood to see if I can pry loose exactly the material spec of aluminum they use in their hubs, since it is not listed on their site, and then to contact ARP which appears by all accounts to be an industry expert in threaded fastener design and manufacture.   I am guessing they will be more willing to help since I favored their studs over Wilwood's.     In case you missed my earlier post, I changed out the Wilwood black oxide studs for ARP cadmium plated ones, due to a personal opinion that black oxide fasteners in aluminum is bad practice.