280Z build w/ LS3 and 2015 Mustang spindles/8.8

[AydinZ71]

Well thanks for the insight guys! I didn’t realize the driveshaft was purposefully flexing the U-joint at a slight angle during rotation. I knew the tranny had a slight down angle, but did not realize the tranny output and diff input where slightly offset in purpose. Always learning something new! 

[280Z-LS3]

Repaired the rust damage on passenger door sill.  Been pouring all my time into the build so haven't had time to fabricate the DIY sheet metal brake from the pieces  I gathered at the local structural iron fabricator remnant pile.  So to form the patch I used some scrap angle and vice to form the 20 gauge patch piece.

 

Edited October 31, 2020 by 280Z-LS3

[280Z-LS3]

Finished up the seam stitch welding, what a time consuming job!  I approximate at least 20-30 hrs invested, maybe more.  Also welded in the Bad Dog frame rails and subframe connectors but before doing so I leveled the body on jack stands just to make sure no stress was flexing the body.  Noticed a big increase in body stiffness while re-leveling on the stands after stitch welding.  The first initial leveling to prepare for stitch welding the body would flex to sit on jack stands and after it pivots on the higher points.  Conformation that all that time and effort was not spent for nothing

 

I welded in the Bad Dog frame rails last because was contemplating incorporating some captive nuts inside the rails for the trans mount.  After giving that idea more thought the complexity of pulling that off just killed my motivation.  Instead going to build the trans mount off of some extra support structure for the floor pan.  The bottom of the S30 chassis is a weak point and would like to address this while cutting up the trans tunnel to fit the Cobra Suzuka seat (my 1975 has the intruding bulge into the driver's seat area).  Heavy85, a member here, crashed his Z into a small boulder field during a hill climb event.  He posted an in car video and after math photos.  His crash hammered home the need to build some strength and crash protection below the passenger seats.  Getting ahead of myself a bit as this has yet to be design...  Here are some pics of progress to date.

 

Some weld thru primer before install of frame rails

 

 

Some standard primer on inside of BD frame rails.  The drilled holes fit over the stock weep holes and were welded to close gap between frame rail.

 

 

Had to remove the stock roll bar mount tabs for welding clearance.  That's okay since the new rear bar will most likely mount behind diff.

 

Welded the portion of plate beneath connector first.

 

Again leveled body on jack stands before tacking connectors in place.

 

Finished product.

 

 

Off to get a beer, Cheers!

 

 

 

 

[fusion]

Great build so far!  Did you use any of the custom tools Ford specifies in the instructions to replace the yoke on the diff?  I need to do mine soon.  Any tips or pictures of that?  Did you just use a standard inch pound torque wrench to get the torque-to-turn measurement?

[280Z-LS3]

I placed the stock yoke in a vice to hold while removing pinion nut and reinstalling new yoke.

Follow the directions for the Ford kit I mentioned in an earlier post.  Basically, measure the torque to rotate pinion gear before removing nut and try to match that amount when installing the new yoke.  Torque and check in increments so you don't over shoot.  Over shooting will further crush the crush sleeve which will then require replacement, that means tearing the whole diff down.

[280Z-LS3]

Started in on the chassis stiffening base plates.  Formed up some brackets/base plates made of 12 gauge (0.101") to slip over the frame rails to support the roll bar area and to wrap the top portion of strut towers.

 

 

I tack welded the plate on then muscled them a bit to start wrapping around tower.  After about 30 degrees of wrap needed a BFH to wrap to a point where a clamp could finish drawing the plate to the tower.

 

 

Been thinking about transverse link bracing/re-enforcement.  Ordered up some tubing which should arrive in a few days.  Here is the rough idea.  Would also like to add tubing in a X shape between link mounts but need to get the diff back in to verify clearance.  

 

 

 

Edited November 7, 2020 by 280Z-LS3

[Richard Oben]

Great work, and a ton of it, when you can't remember if it is 20 or 30 hours it was probably 40 LOL.  The dedication to this is so very cool!  This will be a very fast and safe car.  Well done!

[280Z-LS3]

Thanks Richard.  Really enjoying building all the modifications and applying the knowledge I have learned here on HybridZ.

[tube80z]

On 11/1/2020 at 7:21 PM, 280Z-LS3 said:

I welded in the Bad Dog frame rails last because was contemplating incorporating some captive nuts inside the rails for the trans mount.  After giving that idea more thought the complexity of pulling that off just killed my motivation.  Instead going to build the trans mount off of some extra support structure for the floor pan.  The bottom of the S30 chassis is a weak point and would like to address this while cutting up the trans tunnel to fit the Cobra Suzuka seat (my 1975 has the intruding bulge into the driver's seat area).  Heavy85, a member here, crashed his Z into a small boulder field during a hill climb event.  He posted an in car video and after math photos.  His crash hammered home the need to build some strength and crash protection below the passenger seats.  Getting ahead of myself a bit as this has yet to be design...  

 

I love the level of work you're doing.  The crash comment is one I've thought a lot about too.  About 20+ years ago (vague) I witnessed the aftermath of a Ford Falcon leaving the road at not much speed and hit a tree.  This was well below normal racing speeds (hillclimb event) as the road was wet.  The driver suffered a broken leg, pelvis, and now walks with a limp.  Why I bring this up is that the underside of a Ford Falcon is very similar to the Z cars.  His car had a good cage and a racing seat.  How he got hurt was the car rolled off the door bars when he went sideways into the tree and floor deformed as it was the weak element.  And while he was held in his seat the car deformed and like a large lever broke his leg at the edge of the seat.  To this day I can vividly recall his screams as the emergency crew removed him from the car.  

 

Making the floor stiffer is a good thing in my book.  There are still a couple of areas to think about depending on how you intend to use your car (some could be handled by a cage).  The main one I've seen where there's a problem is the engine compartment to passenger area.  While you have the Bad Dog rail help there's no lateral protection in the front.  I've heard that a few big crashes in Z cars have resulted in broken ankles as this area can fold in on your feet in a wreck.  If you look at new cars they have structure that goes from the inner rail to the outer  and this can be triangulated to the TC and upper strut mounts.  Here's a picture of what I'm talking about.  I have more ideas on fixing the firewall too based on newer cars.

 

 

On 11/1/2020 at 7:21 PM, 280Z-LS3 said:

Here are some pics of progress to date.

 

Some weld thru primer before install of frame rails

 

 

 

 

[280Z-LS3]

Cringing at the description of that crash.  Does not take much to get into trouble.  Physics is a bitch...

 

I am stealing many elements of bjhines' cage and chassis stiffening.  Tying the TC buckets to rockers, upper frame horns to rockers and strut tower to above sway bar frame rail area with 1.5"x0.065" DOM.  I think this size tubing will give enough strength while minimizing additional weight.

 

 

I think you are suggesting adding a tube from rocker (connected to the TC tube) to frame rail along the floor pan where it starts to angle up which is easy to do.  Adding structure from rocker to trans tunnel under seats is easy too but how to carry that strength across the trans tunnel?  Any ideas other than trans mount?  Having the driveline and exhaust mocked up will certainly help determine what is possible. 

 

 

 

Edited November 8, 2020 by 280Z-LS3

[tube80z]

On 11/7/2020 at 7:14 PM, 280Z-LS3 said:

Cringing at the description of that crash.  Does not take much to get into trouble.  Physics is a bitch...

 

I am stealing many elements of bjhines' cage and chassis stiffening.  Tying the TC buckets to rockers, upper frame horns to rockers and strut tower to above sway bar frame rail area with 1.5"x0.065" DOM.  I think this size tubing will give enough strength while minimizing additional weight.

 

I don't think you need to go that large.  I'd use the same tube as you would for a strut bar for the purely torsion stressed members unless you already have the material.  It will just weigh a little more in the end.  

 

On 11/7/2020 at 7:14 PM, 280Z-LS3 said:

 

 

I think you are suggesting adding a tube from rocker (connected to the TC tube) to frame rail along the floor pan where it starts to angle up which is easy to do.  Adding structure from rocker to trans tunnel under seats is easy too but how to carry that strength across the trans tunnel?  Any ideas other than trans mount?  Having the driveline and exhaust mocked up will certainly help determine what is possible. 

 

I think you have a couple options.  You can do it in tube similar to what you have or was used on BJHines car.  The other is to make a larger torsion box out of sheet in similar thickness as the rest of the car.  Look at the convertible torque box mod for Ford mid-to-late 60s Mustangs and Falcons.  They have a very similar unibody design to the Z.  In those they build a box that goes straight down from the firewall and then back into the floor.  This connects to the engine bay side.  Here's a couple of links to give you the general idea https://ironhydroxide.blogspot.com/2017/04/boxes-of-torque.html and https://ironhydroxide.blogspot.com/2017/05/boxes-of-torque-part-dos.html.  I've also seen this extended down to the level of the outer rocker lip and boxed into the inner rail.  

 

Many of the IMSA Zs boxed in the outer section from the upper rail to A pillar down to the rocker.  This makes that more of a torque box out of that section and can tie in nicely with something similar to the convertible Mustang mods.  Getting across the tranny tunnel is going to require a brace under the bellhousing area or you add internal rails that go from the front frame rail up and over the tranny tunnel and down to the next side.  If you look at newer cars you'll see they have integrated a 8 to 12 point cage into the unibody design.  They just do it with folded metal rather than DOM tube.

 

For a street car that may do some track work I think meshing the torque boxes with the tubes in the image above would be a good way to go.  The new Mazda RX8 is a very stiff unibody compared to all their previous cars.  If you look at images of it and compare to older models all these little details start to pop out.  However you go I really like what you've done.  I need to get some projects out of the way so I can get back to cars myself and put this year behind me.

 

Hope that helps,

Cary

 

[280Z-LS3]

Cary, I like the torque box idea.  

 

13 hours ago, tube80z said:

I think you have a couple options.  You can do it in tube similar to what you have or was used on BJHines car.  The other is to make a larger torsion box out of sheet in similar thickness as the rest of the car

 

Do you think 18 or 20 gauge is best for a torque boxes?  Have you ever calculated what a Mustang type torque box could do for a S30 chassis?  I have a 68 Mustang and will analyze the design tomorrow.  From what I recall the bottom of the torque box is made of substantial plate, at least 11 gauge.  That would certainly also help with a side impact transferring the force to the frame rail and wheel collapsing back up into the foot area from off center front impact just like the TC bucket to rocker support bar does.   

 

Trying to envision the benefit of boxing the upper frame horn, a-pillar and rocker.  Is it just adding more support to the upper frame?  Boxing this area is easy and does not interfere with any current plans.

 

Here are some pics of front end bracing I did on my 68 Mustang.  The torque boxes are clearly visible and honestly at the time thought they only consisted of the thick sheet metal connecting the rocker to the frame rail on the under side.  Never gave them much thought other than the early Mustangs did not have any, the 1967 had only one side then Ford decided both sides should get them in 1968 .  In the cabin the floor pan angles up toward the firewall and on the wheel well side the angled up floor pan is clearly boxed in.   

 

The top tube against the firewall which forms the base of the strut tower triangle runs across the top of firewall just under sheetmetal lip providing support for the strut tower to firewall  "export brace".

Edited November 11, 2020 by 280Z-LS3

[280Z-LS3]

Building the roll cage is on the near horizon and that has me thinking of brackets off knee bar for steering column and maybe for Tilton pedals.  I want electric power steering so started thinking of which EPS swap to use.  After reading just a fraction of the info on web I decided to go with the 2002-2007 Saturn Vue option.  Went down to the local u-pick yard and grabbed a 2007 Vue column for $65.  Will order up a Bruno controller with variable assist knob off eBay.  For now I am going to assume that I will retain the same OEM column length dimension to fit seat which is need to fit roll bar tubing.  Still reading how others have adapted and installed the EPS unit so have not decided exactly which method and parts to use.

 

 

Edited November 13, 2020 by 280Z-LS3

[tube80z]

On 11/10/2020 at 11:14 PM, 280Z-LS3 said:

Cary, I like the torque box idea.  

 

 

Do you think 18 or 20 gauge is best for a torque boxes?  Have you ever calculated what a Mustang type torque box could do for a S30 chassis?  I have a 68 Mustang and will analyze the design tomorrow.  From what I recall the bottom of the torque box is made of substantial plate, at least 11 gauge.  That would certainly also help with a side impact transferring the force to the frame rail and wheel collapsing back up into the foot area from off center front impact just like the TC bucket to rocker support bar does.   

 

I'd only use metal of similar thickness to the frame rail, which I cannot remember off the top of my head.  I can check today if needed as I have my race car cut up for a number of mods.  You're spot on to why I'm doing all this.  It isn't so much for stiffness, although that may benefit too.  It's really protecting the passenger compartment from a wheel coming back in via this normally weak area.

 

On 11/10/2020 at 11:14 PM, 280Z-LS3 said:

 

Trying to envision the benefit of boxing the upper frame horn, a-pillar and rocker.  Is it just adding more support to the upper frame?  Boxing this area is easy and does not interfere with any current plans.

 

The main benefit I'm looking for is to add more crushable structure to this part of the car.  I never gave much thought to any of this until I saw how badly the Falcon deformed in a fairly slow accident.  Up to that point I was totally fine hurtling myself down the road at triple digit speeds thinking my cage and extreme skill  would protect me.  By making more of a box on the corner it connects the upper rail, inner rail, and top rail.  The top rail now has a shorter span and should be stiffer.  

 

 

On my race car there's no cowl so I only have the firewall with no support.  My cage will look overly complicated and heavy but only the required safety tubes need to be full thickness.  The rest are of the same diameter but much thinner.  The green line goes from the lower rail to the upper rail to the top strut mount.  The yellow rail is tubing the sits on top of the normal engine frame rail, this is somewhat weird but based around some stupid SCCA rules that I'm working around.  The tubes that connect the corner to the yellow tubes are what usually go to the TC pickup point.  The idea behind all this is not only to make the car stiffer in torsion and bending but help protect the foot box in case I hit something hard enough to drive the wheel into this area.

 

 

 

On 11/10/2020 at 11:14 PM, 280Z-LS3 said:

 

Here are some pics of front end bracing I did on my 68 Mustang.  

 

The top tube against the firewall which forms the base of the strut tower triangle runs across the top of firewall just under sheetmetal lip providing support for the strut tower to firewall  "export brace".

 

So it looks like you're well versed in all this.  Nice work, BTW.

 

Hope this helps,

Cary

[280Z-LS3]

Update time!

 

Since I am making my own engine and trans mounts I needed to think about drive line angles.  After mocking up the engine/trans assembly decided 2 degrees engine/trans reward tilt gave me the best placement for bellhousing (above frame rails), intake manifold off firewall, harmonic balancer to steering rack clearance, positioning of transmission in tunnel, etc...  To have the pinion angle an equal and opposite 2 degree up necessitated modifying the the 8.8 diff cradle as it positions the pinion with around 4 degrees up.  I dropped the rear mustache bar plate about 3/8" which effectively raises the rear of the diff giving the 2 degrees up pinion angle.  I basically removed the mustache bar mount bolts then jacked the diff up until I achieved desired angle then using the bolt holes in the mustache bar scribed where the new hole locations should be.  I elected to to just move the hole plate rather than drilling new holes.

 

 

Here it is installed.  Cradle not fully welded yet.

 

Now that the diff angle is set moved onto making some puck style engine mounts.  Originally planned on coming off cross member frame like Hoke did in his kits.  However, I ran into some clearance issues in keeping with the criteria of having the engine as far back and low as possible.  The engine is to be set with the block to trans mounting face about 1.5" off the firewall.  Having the engine this far back complicates having the engine mounts connected to the cross member.  I have a three stage scavenge pump mounted on the lower passenger side in the stock a/c compressor location.  I believe the scavenge pump occupies the same physical space of the a/c compressor because it is said to be compatible with the Corvette C6 engine mounts.  Anyway, the amount of cantilever to get behind the scavenge pump seemed too large, somewhere around 4.5" from rear face of cross member, thereby creating a large torque arm that would flex/twist the cross member under WOT.  Would have liked to move the engine slightly more forward (around 1/2") for more engine mount to steering shaft clearance but was prevented by the sump tank return oil fitting on the ARE dry sump pan (no pic, sorry).  The fitting sits just behind the passenger side steering rack mount.  I ended up with about 1/2" clearance between the oil fitting and steering rack.

 

 

So on to plan B, have the engine mount come off frame rails.  Using some cereal boxes I mocked up some mount templates.

 

 

 

The driver's side mount does not have much overlap on the engine plate so I cut some gussets to weld to bottom to help distribute the load across the plate.  I don't have a pic of those mocked up but you can see them on the bench.  Will post when they are welded up.  Here is a pic of the passenger side mocked up on bench with  9" 3/16" thick angle to reinforce the frame rails.  The mounts themselves are made of cut 3"x.250" square tubing.

 

 

 

 

Moved onto designing the trans mount which I am still in the process of figuring out.  I need to get the Suzuka seat installed because that necessitates some trans tunnel surgery. where the trans mount will reside.   My 1975 has the driver's side trans bulge for the catalytic converter competing for space.  Here is the initial hole.

 

 

And that's still may not be big enough!  But before attacking the poor car again with the cut off wheel waiting on some OMP seat mounts.  The really nice Cobra alum brackets purchased with seat have too long a foot print plus they sit really high.  Cobra's description of these brackets say they offer the most adjustability but that just means they have the ability/material to drill some new holes and cut away material for lap belt clearance.  Too much hassle for a guy that does not have a mill...  Anyway the OMPs are 5cm or 2" shorter length and around 3cm lower in height.

 

While waiting for the OMP brackets moved onto the front upper frame horn and T/C bucket to rocker supports.  Used 1.5" 14 gauge square for the frame horn and 1.25" 14 gauge for the T/C bucket.  The bend at the firewall on the frame horn tube is 8 degrees (pie cut sides and welded) and choose square over round tube for ease of stitch welding to body panels.  T/C tube square only to match.

 

 

 

 

 

 

That's all for now.

 

[fusion]

Nice progress.  I am going to be installing my super 8.8 soon.  When you say that "I elected to to just move the hole plate rather than drilling new holes", what do you mean by this?  Did you cut out part of the cradle and reweld lower?  Got any pics?

 

Do you think slotting the holes would be too risky?

[280Z-LS3]

16 minutes ago, fusion said:

Did you cut out part of the cradle and reweld lower?

 

No pics.  I have the "you weld" kit that comes tacked welded together.  It was easier to just break the tacks on the mustache bar mount plate and move the corresponding amount to achieve desired pinion angle.  Three things to look out for are resulting tightening clearance between frame rail and cradle (you are moving the cradle up), potential bind in the bushings on the two trans tunnel uprights (may have to break the tack welds and reposition the bushings cups on the plates) and check for pinion to forward transverse link clearance (pinion has moves down).  Have not heard anyone with vibration issues with the Super 8.8 kit so this was not to fix any problem.  I just am a hobbist who wanted things spec'd out at 2 degrees for the reasons I detailed above so take that for what it's worth.

 

30 minutes ago, fusion said:

Do you think slotting the holes would be too risky?

 

I would NOT slot the holes.

 

[280Z-LS3]

Well, I have been racking my brain trying to get the Suzuka seat to fit.  The widest point of shoulder bolster is 590mm and 500 mm from base of seat per Corbra diagram spec.  Centering the seat on the steering wheel puts the shoulder bolster out past the door card.  In fact, it looks like if the door were cut for clearance the shoulder bolster would extend past the window slot in the door.  That means no window, no bueno!  Measured the steering center to door face when closed is 300mm.  Figured installing seat on center of wheel would yield a slam dunk quick placement with maybe a little touch on the door card given 590/2=295mm.  Obviously there is more going on here...

 

 

Most aftermarket fixed back seats are at least 590mm wide at bolsters.  However, the height of the widest point off the base of seat does vary from short 500mm to 650mm.  I don't see how a bolster positioned higher helps because it looks like the window will still get hit but guys have installed seats with these specs.  Were they installed off center to the right of the steering wheel?  I am short at 5'7" so need the seat more forward which places bolster near the door lock pull, farther back and my short legs start reaching for pedals.  (This has me thinking about the length of steering wheel or moving pedals closer but that's a topic for another day).  Maybe successful installs of similar sized seats depend on getting the seat moved way back putting bolster next to B-pillar? 

 

At this point success getting the Suzuka to fit seems slim to none.  Damn shame because it fits me well.

[280Z-LS3]

Returned the Suzuka to HMS Motorsports.  This company has a bunch of great employees and deserve a shout out.

 

After some seriously agonizing seat searching ordered up a 14" Ultra Shield Pro Road Race with 21.75" width.  The new Bride Xero VS is promising coming in at a narrow 520mm but it's back ordered till at least Feb 2021.  Beauty of an aluminum seats is the shoulder bolsters can be bent or even trimmed so if it's close to fitting out of box then I'll make it fit.  I have been told having the seat off center of steering wheel is not that much of an issue but personally I think it would bother me to no end hence the search for a narrow seat.

 

While waiting for seat moved on to making roll cage bases for the main hoop and forward bars.  Both came in at around 12 sq.in. above the SCCA 9 sq.in. minimum.  Will only tack weld these into place which will enable me to drop the cage to weld top bars after all bars have been fitted.  The rear are made of 12g plate and the fronts were made from cut down 2.5" square tubing and 12g plate.  Oh, my bar will be made out of DOM 1.75" 0.95" wall.

 

 

Also killed some time repairing some rust damage and making room for dry sump tank.  Will post up pics of finished sump tank area soon.

 

 

 

 

 

Edited December 19, 2020 by 280Z-LS3

[Ironhead]

It all is looking great.

 

Be sure you give a lot of thought to how you are going to final weld all the awkward parts of the cage.  The urge is to tightly tuck all the bars as close as possible to the bodywork, but if you go too far with this you can wind up with almost unsolvable welding access issues.

 

In my case I found the welding of the bases of the main hoop and the "A" pillar bar to be....challenging....and I think I left a bit more room than it appears you have in mind.  In retrospect it might have been easier to TIG weld those areas, using a big gas lens and lots of stick-out.  Trying to MIG with an inch plus of wire stick-out basically just makes a mess.

Edited December 20, 2020 by Ironhead