Transaxle Mounting — Top Bracket

The stock approach to mounting the drivetrain utilizes two solid motor mounts, two transaxle adapter plate brackets and, in some cases. a small hanger at the back of the rear chassis brace. While this cantilevered approach works fine, I’d rather have more than two or three mounting points.

Why? The monocoque tub is crazy stiff, but the rear section is a tube ladder without any diagonal bracing. In addition, the stock transaxle adapter plate brackets provide a lot of structure and I need to change them to make room for the merge collectors. Lastly, I don’t want any chance that the engine or transaxle would come free in a bad wreck.

Since the engine is hard mounted, I decided to utilize the transaxle as a stressed member with a total of nine mounting points:

  • A top bracket mounted to the back of the rear chassis brace, the same location that many builders add the aforementioned hanger. The bracket bolts to the transaxle’s billet bulkhead plate.

  • Four indexed tubes with rod ends that connect the top and bottom of the rear billet chassis pieces to the transaxle’s bulkhead plate. The tubes are configured in an “X” pattern which triangulates the gearbox on both sides. These replace the single tube on each side that connects the bottom of the billet piece to the underside of the rear chassis brace. While these stock tubes add some structure they have a very shallow angle (i.e., poor triangulation) to provide room for the standard location for the exhaust. The “X” pattern will significantly increase torsional rigidity in this area.

  • Four dog-bone brackets connecting the middle billet chassis pieces to the billet bellhousing. These replace the stock transaxle adapter brackets.

    This approach is similar to how Agile Automotive builds their endurance SL-Cs. The first step is to fabricate a top bracket. This is complicated by the location of the rear sway bar and that my engine is in the stock location (Agile both lowers and slides the engine forward).

Rear chassis brace, sway bar and transaxle top bracket

As can be seen in the image above the solution was a removeable bracket that bridges the sway bar. The top and bottom plates are 3/16” 4130 and the side and back plates are 1/8” 4130. I considered recessing flat mounting plates into the top and bottom of the brace’s 1.5” round tube, but I realized that incorporating a 1.5” square tube with a 1/8” wall would be easier to fabricate and would increase the strength of the brace. In addition, the square tube projects beyond the round tube thereby reducing the distance that bracket needs to bridge over the sway bar. Three 4130 crush (I suppose anti crush would be more accurate) tubes are welded into both the rectangular mounting tube and the top bracket.

Top bracket (left) and square mounting tube (right), each with three crush tubes (purple)

The rectangular mounting tube (green) extends past the brace and reduces the distance that the bracket needs to bridge over the sway bar

The rear chassis brace (shown upside down) has been cut to receive the square mounting tube. The two tabs marked with X’s will be removed.

Top bracket finished

Two half-inch spacers between the bottom of the bracket and transaxle’s bulkhead plate

Two half-inch spacers between the bottom of the bracket and transaxle’s bulkhead plate

The top bracket is finished and the sway bar brackets are welded. The next step is to fabricate four tubes and associated brackets that connect the top and bottom of the rear billet chassis pieces to the transaxle’s bulkhead plate.

Over Clocking the Starter

The starter has a machined aluminum flange that allows it to be clocked in four positions. However, even when clocked all of the way up, the starter was hitting the merge collector. D’oh! I unbolted the motor from the bracket, rotated it and confirmed that it could be clocked enough to clear the merge collector if new holes were machined.

Two holes shouldn’t be a big deal, right? Not exactly. The new holes intersect the existing holes requiring the existing ones to be welded closed and machined. In addition, the geometry requires both the shoulder that indexes the bell housing and the mounting holes to be machined on an arc that’s concentric with the motor’s shaft. Unless you can write your name on an Etch A Sketch (if you’re too young to know what one is Google it), the best way to accomplish this on a manual mill is with a rotary table.

6” rotary table mounted to the X/Y table

I had been thinking about buying a rotary table for a while so this was a good excuse to get one. Centering the table under the spindle with an indicator mounted to an arm is a real pain-in-the-ass because the gauge rotates with the spindle which makes it hard to read. After doing a little research I bought a coaxial indicator. You hold the long horizonal arm (or let it bind on something) to keep the gauge from spinning. Mine supports a max of 800 RPMs. Anything over a couple of hundred RPMs provides instantaneous feedback to changes, making it easy to figure out which handwheel to rotate in which direction to get everything centered.

(Left) indicator mounted to an arm (right) coaxial indicator

The next challenge was centering the part on the rotary table. Centering the rotary table was relatively easy because it’s mounted to the X/Y table and the milling machine’s handwheels reliably move the table one thousand of an inch along the X or Y axis. However, adjustments to the bracket need to be done with your hands and even when you get everything centered you can inadvertaly nudge things when clamping the part.

Custom mounting plate and three-jaw, self-centering chuck

Since the starter bracket has a large round opening the solution was to purchase a three-jaw self-centering chuck. To mount the chuck to the rotary table I fabricated a mounting plate from 3/8” aluminum and affixed it with three M10 flathead screws. To center the chuck on the rotary table I did the following:

  • Mounted a precision-ground 3/4” stainless rod in the spindle with a 3/4” collet. A drill chuck isn’t as accurate.

  • Positioned the rotary table/chuck assembly under the rod and lined it up by eye.

  • Lowered the rod into the chuck.

  • Tightened the chuck on the rod. Since the adapter plate/chuck haven’t been bolted yet this perfectly centered the chuck on the rod.

  • Bolted the adapter plate to the rotary table.

  • Zero’d the DROs.

3/4” precision-ground stainless steel rod used to center the chuck on the rotary table

To indicate the hole circle I positioned the X-Y table such that a tight-tolerance drill bit could be plunged, with the machine off, into one of the existing holes via the quill. To ensure that everything was concentric I rotated the table 180 degrees and validated that I could plunge the bit into the opposite hole. I then determined that the new holes should be 31 degrees from the closest existing hole (the one in between had been welded closed).

Now that everything was fixtured and centered, it was time to stop fiddling and to make some chips so I:

  1. Deeply countersunk the two rear holes to allow the weld to fully fill them.

  2. Welded the holes closed from both the front and back.

  3. Removed the excess weld beads:

    • Faced the back of the flange to ensure that it sits flat against the motor.

    • Faced the top of the shoulder to ensure that it sits flat against in the recess in the bell housing.

    • Machined the OD of the shoulder to ensure that it’s concentric with the hole in the bellhousing.

  4. Drilled the new holes from the back.

  5. Countersunk the new holes from the front so that the screw heads cleared the bell housing.

  6. Deburred all of the edges.

The back has been machined and the front is about to be be machined. The weld beads were intentionally large to ensure that the prior holes and countersinks were completely filled.

The back has been machined and the front is about to be be machined. The weld beads were intentionally large to ensure that the prior holes and countersinks were completely filled.

The new hole has a button head screw in it. The old hole and countersink were between it and the next hole, but you can’t tell they were even there which was the whole point of this exercise.

I wasn’t able to get the bracket on the starter once everything was done. WTF?… After a brief panic I realized that I didn’t machine the relevant surfaces. It was a tight fit before and the welding process must have slightly distorted things. Fortunately I had a flap sanding drum that perfectly fit the hole and with a little tweaking everything fit again.

Custom Crossunder Flanges

While my type of exhaust is commonly called a 180-degree crossover, my primaries cross under the the oil pan rather than over the bell housing. So I guess it’s a 180-degree crossunder. To allow the headers to be installed/removed the left and right sides will be split via flanges under the middle of the oil pan. I was unable to find anything appropriate so I designed a profile and had them CNC machined from 3/8” 304 stainless steel. To minimize the overall height the tube center-to-center spacing was increased to allow the bolt holes to move towards the middle.

Collector Dummies

Icengineworks offers 4-1 collector dummies that would be perfect for formed collectors. However, I have fabricated double-slip collectors that have slightly wider on-center tube spacing. In addition, the 180-crossunder design requires that both sides are mocked at the same time. This necessitates two dummies at a cost of $199.99.

So I decided to design and 3D print eight female adapters. These provide the perfect spacing, were printed faster than over night shipping and cost less than ground shipping for the other pieces.

Merge collector with female adapters installed (the double-slip fittings aren’t shown), 2.0” OD block with the male end up (yellow), front side of the female adapter and back side of the female adapter.

Quick Release

I spent a fair amount of time looking for a high-quality quick release for my steering wheel and my search came to an abrupt end when I found the Krontec QR-03. It’s a radical departure from the spline-based designs that dominate the market. It has the following advantages:

  • It’s impossible to misalign the steering wheel

  • Zero play

  • No splines to wear

  • Smooth and easy spring-loaded action

  • Positive indication of when it’s locked

  • Optional 22-pin motorsport connector

I bought it a couple of years ago and now that I have machined the steering wheel boss it’s time to get it mounted. I drilled a 6-hole, M5 x 70 mm hole pattern in the boss, but I couldn’t mount it directly to the quick release because I need space for wiring. To accommodate this requirement, I purchased a spacer from Krontec and I machined a mounting plate from 1/4” aluminum. The mounting plate serves two purposes; it relocates the mounting holes so that they don’t get too close to the OEM holes in the steering boss and, when combined with the spacer, it provides the proper amount of room for the wiring.

From upper left to lower right; quick release, spacer, flat head screws, steering boss, mounting plate, socket head cap screws, washers and nylocs

From upper left to lower right; quick release, spacer, flat head screws, steering boss, mounting plate, socket head cap screws, washers and nylocs

Six flat head screws affix the mounting plate to the spacer and steering-wheel side of the quick release and six socket head cap screws affix the mounting plate to the steering boss. The flat head screws can’t back out because they’re retained by the steering boss. I had to cut all 12 screws to get the perfect length, but that’s how these things go.

While the stack looks tall the overall height is about an inch taller than the steering boss was before I modified it. This will help me fit a modified OEM steering wheel.

Mock Mufflers

I’ve been busy mocking the exhaust system. Everything up to and including the catalytic converter will be 321 stainless steel and everything after will be titanium. Titanium will minimize the weight behind the rear axle and it should provide a slightly different sound… not to mention look cool. Since I’ll have exhaust cutouts I’d like the primary exhaust to be relatively quiet. The plan is to run two mufflers on each side:

  • Round muffler, 3.5” inlet/outlet, 10” long body (12” total length) with 4.6” diameter

  • Hard 180-degree, fabricated from two mandrel-bent hard 90’s

  • Oval muffler; 3.5” inlet/outlet, 10” long body (12” total length) with 6” x 9” oval profile

The challenge is figuring out if it they will fit and if so, how. I bought some 2” pink insulation foam at Home Depot and cut the muffler profiles on a bandsaw. 3-1/2” deck screws were used to attach the pieces and three pieces of 1/4” plywood and two pieces of scrap aluminum right angle were used to mock the 180-degree tube and to space the mufflers apart.


After some fiddling the best fit was with the oval at the bottom with its center offset by several inches from the round muffler and rotated such that it was parallel to the ground. I was already planning on stretching the tail to match the curvature of the tail lights and it looks like I might need to stretch it a few inches further to get the oval muffler to fit. In addition, I’ll need to create a bucket for the tail light, wrap it with heat shield and create a thin vent above the tail light to let heat escape.

The next step is to figure out how to connect the tube from cat to the mufflers and the tube from the mufflers to the tips. This will be accomplished with a bunch of pie cuts.



Steering Boss Double Take

I want to run an OEM steering wheel with a quick release. That combination isn’t common because the quick release takes up space, modern OEM steering wheels are deep to accommodate an air bag and stacking the two moves the steering wheel too close to the driver.

The adjustable electric power assist (EPAS) column from DC Electronics (DCE) doesn’t contain any stalks and I was planning on welding an adapter to keep everything as compact as possible. However, the column contains a pressure sensor which would be damaged by the heat. According to DCE I would essentially need to destroy the column to remove the sensor. There goes plan A.

Plan B was to adapt a steering boss to fit the spline. This was when I learned that the column is sourced from a Renault. Unfortunately the spline is some proprietary French invention (D’oh!) and DCE indicated that the only aftermarket steering boss was available from MOMO. So I was in a bit of steering wheel boss hell…

In heaven the French are the cooks, the Germans are the engineers and the English are the police. In hell the French are the engineers, the Germans are the police and the English are the cooks.

The MOMO steering boss has a steel spline and a steel collapsible section cast into an aluminum hub. The collapsible section takes up a lot of space and isn’t required because I have a custom lower shaft that provides over four inches of zero-resistance collapsibility BEFORE the steering wheel hits me. So I cut the steel section off with a bandsaw and faced the surface on a lathe. I was concerned about machining the steel embedded in the cast aluminum, but that went better than I expected. It was at this point that I realized that I’d need to remove the outer aluminum shell to accommodate the six mounting screws for the adapter. Once that was done I realized that I’d also need to machine the inner hub as well. All in all a lot of time on the lathe. As can be seen in the picture below there were some air pockets which don’t provide a warm-fuzzy feeling.

To accommodate the 70 mm hole pattern for the quick release the outer shell had to be completely removed and the OD of the inner hub needed to be reduced

Air pockets in the MOMO cast aluminum

MOMO unit with collapsible section cut off, outer shell removed, inner hub reduced and six mounting holes drilled. Note the steel pieces that remain in the hub.

MOMO unit with collapsible section cut off, outer shell removed, inner hub reduced and six mounting holes drilled. Note the steel pieces that remain in the hub.

Joel, who also has a DCE EPAS, mentioned that OMP makes a compatible steering boss so I ordered one from eBay in the UK. Unlike the MOMO unit, the steel collapsible unit is attached with four screws. I was then able to quickly machine the front and rear faces. I didn’t like the lip on OD, so I cut it off in a lathe. Once machined, the OMP is about 0.8” shorter than the MOMO.

Front side of OMP being machined

Backside of OMP. I probably didn’t need to machine this side, but I wasn’t sure how I was going to mount the quick release and it was easy to do. The lip which I also machined off is the outer ring sitting on the wood table.

MOMO on left and OMP on the right. Removing the outer shell on the MOMO reduced its OD. The MOMO has been drilled with the six holes to mount the quick disconnect whereas the OMP hasn’t been drilled yet (the four holes were used to mount the collapsible section).

MOMO on left and OMP on the right

For my purposes, the OMP unit is a much better starting point. Less machining, no air pockets or steel remnants in the casting and a reassuringly robust piece.

Rear Brembo GT Brake Fitment Issue

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I have the Brembo GT brake upgrade and the supplied banjo fitting collides with the toe link arm and the lower bump steer bushing. It’s not even close. In the picture above the blue plug is where the banjo goes, but the supplied Brembo banjo fittings, let alone the banjo bolts and crush washers, won’t fit. The pile of nice discarded parts grows again.

To address this, I had to modify two parts. I machined a flat on the toe link arms with a mill. While the cutting process was straight forward, it was a pain-in-the-ass to fixture due to its awkward shape. I considered milling a flat on the lower bump steer spacers, but I assumed that they would rotate such that the flat was no longer aligned with the flat on the toe link arm. For this reason, I turned turned them on a lathe.

Even then things didn’t fit so I needed to find some new parts. Nobody specs the height of their banjo fittings, banjo bolts or crush washers so I had to call a bunch of places and get someone in tech support to either measure one or look it up in CAD. I wound up with parts from several suppliers, but as can be seen below, everything fits.

Abe used his hydraulic crimper to fabricate custom flex lines. They’re PFTE with braided stainless steel and a rubber covering. I 3D printed a bracket to keep the brake line in place. The brake line hole is oversized and has a large chamfer (shown in blue) on both sides to allow the brake line to slide back and forth as the suspension moves. I don’t think that heat will be too bad there, so the Onyx should hold up. If not, I’ll change materials.

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Rear Hubs v2.1

I completed the upgrade to the 33-spline ZR1 hubs and Driveshaft Shop stub axles. I’m not sure how other builders machined the recesses for the socket head cap screws, but the approach that I took was quick and straightforward. I purchased the following counterbore and removeable pilot from McMaster (the pilot slides into the counterbore and is held in place with a set screw):

  • (31125A37) Carbide-Tipped Counterbore, 3 Flutes, 23/32" Diameter ($89.01)

  • (3103A32) Steel Counterbore Pilot, 3/16" Shank Diameter, 1/2" Pilot Head ($7.43)

I wanted the pilot to have a close fit to ensure that the counterbore was concentric and a 15/32” pilot had too much play so I purchased a 1/2” one and used a lathe to obtain a perfect fit. This made indexing the counterbore easy… if the pilot drops in the hole, you're good to go. I used a mill, but I think a drill press with low runout would have worked fine. The picture below shows that the fit is excellent — wall clearance is about ten thousandths. The counterbore does cut into the 1/4” hole which is used for dowels that hold the triangular spacer on the other side of the upright. Since the dowel isn’t long enough to reach the machined section this isn’t an issue.

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Standard washers won’t fit in the counterbored hole so I used special washers to keep the screws from galling the upright. The screws are M12 x 1.75 mm by 55 mm long. I hate iron oxide because it rusts and I couldn’t find zinc-plated ones in the correct length, so I cut longer ones down and polished and painted the tip — I think my OCD can live with that LOL.

Left to right; M12 socket head cap screw, standard M12 washer, and socket head cap washer

Most builders chamfered the ID of the upright, but Agile Automotive suggested that I machine the stub axle rather than the upright. I assumed that it would be a nightmare to machine because they were hardened, but Agile pointed out that if they were too hard they’d become brittle. Agile was correct and I didn’t have any issues machining them. This is a quicker and simpler process than machining the upright which would require it to be carefully indexed on a rotary table and cut with a decent sized chamfer end mill. To machine the stub axle you just chuck it up in a lathe and go. I took ~0.040” off of the stub axles which provides about 0.015” clearance between the stub axle and the upright.

All of the stub axles pictured below were sourced from The Driveshaft Shop. From left to right; stock 30 spline, unmodified 33 spline and modified 33-spline. The stock piece is a standard part for a Nissan. The larger cone allows it to clear the upright’s ID, but the taller spline extends past the hub and you must use a doughnut-shaped spacer between the spine and axle nut so that the axle nut binds on the hub and NOT the spline. The stock unit is fabricated by press fitting the spline into the cone and welding a nut on the backside. The 33-spline units are machined from a single piece of billet, do not require a spacer and are rated to 1,800 HP.

I forgot to take a picture before I painted the machined surface so I added a white line to illustrate the surface that was machined. Because the mounting flange is shorter I will need longer axles which will reduce the angle of the CV joints (i.e., place less stress on them).

To accommodate the sensor wire, I drilled the ID of the hub into an unused bolt hole and carefully deburred both sides of the hole. I then de-pinned the connector… well, after spending 15 minutes attempting to de-pin it I spent about 20 minutes trying to carefully cut it apart to maximize the length of wire and pinched my finger. The second connector took a second to snip off LOL. I will encase the wires with something to protect them from the edge of the hole and re-terminate them with Deutsche connectors. In addition to being superior to the OEM connectors, they are easy to de-pin.

Sensor wire routed through hole drilled in the upright’s ID


Headers Prototyped

I sure as hell hope that the 180-degree crossover exhaust sounds good because it’s a lot work. Like everything else, there’s a learning curve. The first step was to mock the tubes that cross under the oil pan. The longest crossover tube sets the length of the other seven tubes so you want it to be as short as possible.

It looks like I’ll be able to get them all to be 38” long, but I still need to finish the #2 and #8 tubes on the right side. The pictures below show the left header. The two middle tubes (#3 and #5) cross under the oil pan and the front and rear tubes (#1 and #7, respectively) take a circuitous route before feeding the left merge collector. The merge collector is located where the stock transaxle adapter plate bracket is located. I will replace the stock bracket with a dog-bone bracket leaving that desirable space at the bottom open. A custom four-tube flange will be located under the middle of the oil pan allowing the left and right headers to be separated.

The plywood is the underside of the car, the blue tape on the plywood delineates the lower 2” x 2” chassis rail and the green tape delineates the upper rail. Each piece of yellow tape indicates two cuts and a weld.

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The icengineworks blocks are extremely useful and I’ve learned a couple of tips:

  • Use a Sharpie to write the centerline radius (CLR) in the same location on every block before you start. This will save you a lot of time trying to read the molded print — or maybe I’m just old. This will also help prevent a different CLR being inadvertently inserted into a bend.

  • Always have a J bend and/or a U bend of every CLR on hand. It’s a lot easier to hold various CLR sections up to see what fits best vs. snapping one piece on at a time.

  • A plastic engine block next to the car on a lift provides the best of both worlds for checking fitment.

  • If you drop a piece and it splits apart use Crazy Glue to stick the two halves together. If you snap them back together without the glue, they may pop apart and cause a whole tube length to fall on the floor.

  • When you count the blocks to determine how long the tube is at a given point, put a piece of tape on the block and write the number down.

  • Use a stable piece of plywood under the engine. If a tube drops it won’t go far. If you let it hit the floor, you’ll need to start over again.

  • Long tubes get heavy and they can rotate or fall off. If you have plywood under the engine you can place blocks under the tubes to support them. I used step blocks from my milling machine’s clamp set because it’s easy to quickly adjust their height.

Step blocks

Sacrificial Lamb

My wife came home one day to find this 1970 Cadillac Deville parked in the driveway. “Whose car is that?” she asked in a highly-agitated tone. “Mine,” I responded. She didn’t believe me until I showed her the title.

Apparently the large fuzzy dice hanging from the mirror pushed her over the edge. There hadn’t been that much marital controversy since I installed the functional porcelain sculpture in the boiler room. I would like to point out that the wall-mounted Purell dispenser made it the only COVID-ready part of the house LOL.

So why did I subject myself to this wrath? In a word, regulations. There are a bunch of steps to register a non-OEM car in Massachusetts. One of the most challenging is obtaining an emissions exemption. There are three ways to accomplish this:

  1. Prove that the car has a pre-emissions motor (i.e., pre 1974). You need a receipt with the VIN on it for the State Trooper salvage inspection. After several other steps you schedule a meeting at a MAC center where they put the car on a lift and inspect all of the casting numbers to certify the age of the engine. You then need to provide a table which illustrates that all of the final gear ratios are the same or higher than the car from which the engine was sourced. My cobra has a 1966 427 side oiler so this approach worked for that car, but it’s not applicable to the SL-C.

  2. Use an approved drivetrain which includes engine, transmission and ECU. I think they also require the same differential and wheels. In any event, I couldn’t take this approach because there are no combinations which include a transaxle.

  3. Purchase a pre-emissions car with a displacement larger than than the new engine and insure, register and inspect it for at least one year in MA. Then take it to a salvage yard so that “The chassis, frame, body tub, and engine will be completely destroyed in a manner that prevents their reuse as motor vehicle parts” and complete the paperwork which states that there are “significant penalties, including, but not limited to, possible fines and imprisonment, for submitting false, inaccurate, incomplete or misleading information.”

I had found a less-expense car, but when I met with the person selling it I learned that he was selling on behalf of his recently deceased grandfather who had bought it new, garaged it and personally serviced it for over fifty years. It seemed like bad karma to crush it so I kept looking.

Since my engine is custom built I didn’t want to get into an argument that the displacement might be slightly larger than 427 CID. The Cadillac has a 472 CID so there can be no debate that it’s larger. The three guys who crushed the car were upset. They kept asking “why” would someone crush a perfectly operating car. In a word, regulations.



Parking Brakes Installed

The electric parking brakes are installed. I had been waiting to upgrade the rear uprights before finalizing the bracket design. Unlike the prior uprights, the new uprights are symmetrical and feature a thicker center web which comfortably accommodates a M10 screw. This makes drilling and tapping the holes to mount the bracket straight forward. I 3D printed mock brackets to ensure a good fit before having them CNC machined.

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The heads of all of the screws (e.g., two in the bracket and two in the caliper) will be drilled to accommodate safety wire when the car is done. I plugged the two connectors into the ECU, applied 12V and depressed the supplied button for three seconds and everything worked beautifully.

The parking brakes are done until the wire harness is made. The ECU is in a potted aluminum case so I have a lot of flexibility on where to locate it. There are two wiring approaches:

Standalone: Modify the parking brake (PB) harness and keep it independent. I would shorten the caliper-to-ECU wires and lengthen the button lead so that it reached the cockpit.

Integrated: Tie it into the MoTeC system:

  • Connect the PB switch to a MoTeC output on the tail Power Distribution Module (PDM).

  • Connect the status wire (i.e., the one that lights the parking brake LED) to a MoTeC input on the tail PDM.

  • Use a MoTeC CAN bus switch in the cockpit to control the brake. Their switches have three indicator LEDs (red, orange and green) so I’d configure all to be off when the parking brake is disengaged and for the red to be lit when it was engaged. While MoTeC is anything but a DIY system, this type of logic can be easily configured via their free Windows-based software.

If I have enough inputs and outputs available, I’ll for with the integrated approach.

External view

View from the engine compartment outwards

Top view

First Air Jack

The SL-C got air jacked for the first time today! Note that the stainless steel flex lines and the mount for connector/valve are temporary.

Getting the air jack system up and running was more work than I expected. The lift brackets were completed just over two years ago and mid last year the aluminum hard lines were installed, but I wasn’t able to find a system that I felt safe flowing 30 bar (435 psi) to test things.

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I discovered the Paoli booth at the Performance Racing Industry (PRI) show last year. Apparently they have motorsport credentials. I tried to order some equipment from them, but they offer a bewildering number of fittings and the catalog, while pretty, doesn’t help you put a system together. I kept asking for them to spec a system for me which is apparently a foreign concept.

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I spoke with Hill McCarty at Agile Automotive and he agreed to supply the system. I felt better when he had some of the same issues that I experienced. He ordered the system just before Covid exploded and, as Paoli is based in Italy, the order was understandably delayed for months. It arrived damaged so Agile ordered a replacement part and subsequently shipped everything from Maryland to Boston. UPS lost it for over three months and put Agile through the ringer when they made a claim. That probably took another three months. UPS finally found it in Texas, shipped it to me, and when it arrived a couple of the fittings didn’t match up and Agile had to chase Paoli for three weeks to get an answer.

The Paoli nitrogen system (bottle, trolley, regulator, quick disconnects, fittings and hose) and the AP Racing system (air jacks, connector/valve and wand) are well made. The three jacks (one in front and two in the rear) result in a stable car. As seen in the video, you simply slam the wand into the connector to raise the car. The wand can be left plugged in to compensate for any leaks or it can be immediately removed. The car is dropped by pulling the valve backwards. The video shows the car being raised at 300psi which is well under the 435 psi max. My guess is that even when fully loaded I can get it to raise faster than shown. I can also raise it gently by slowly increasing the pressure on the regulator.

So was it all worth it? Hell yeah! I’m thankful for all of the hard work that Agile put into making this happen. If you’re looking for a nitrogen system, they now know exactly what’s required. Better yet, they ordered another system to replace the one that UPS lost so they might have one in stock.

Stub Axle Spline too Long

Earlier this year I took the suspension off to have a bunch of the steel parts plated (details here) and yesterday I finally got around to putting the upgraded rear uprights, stub axles and hubs (details here) on the car. Everything went smoothly except that after torqueing the stub axle nut I gave the wheel a tug and it moved. I was able to move the wheel about 1/4” towards and away from the car with no effort. That’s not right! I tried the other side and it significantly less, but unacceptable, play.

The picture below shows the side with less play. You can clearly see the spline projecting past the hub so the nut is going to bind on the spline’s shoulder and not the hub.

The spline is projecting past the hub causing the nut to bind on the spline rather than the hub

So why does one side have so much more play than the other? If you look at the picture below you will note that the threads on the left stub axle aren’t cut as far as the one on the right so the nut bound where the threads stopped on that side resulting in additional play.

The right has more threads than the left

Bob is the only other person that I’m aware of who has upgraded his rear uprights. While his car isn’t registered yet, he’s had it on a dyno and he’s done a couple of hole shots. He torqued his stub axle nuts, but when he gave his wheels a tug last night he had the exact same problem.

Location of the part number

Location of the part number

Superlite has been shipping the upgraded parts on new kits for quite a while, but I haven’t heard about anyone having this issue before. Bob and I have the same SKF Corvette Racing Hubs, but they’re OEM replacements so that shouldn’t be an issue. Do you guys with the newer uprights have this problem? Did Superlite provide a spacer? Do you have the same stub axle?

Upright: SL-RR-UR-02RL
Stub Axle: 108-NI-O-HUV

Lower Rear Control Arm Machined

The screws holding the rear ball joints in place are too long, something that’s bothered me since the car was delivered. I thought I’d replace them with shorter ones. That shouldn’t take long, right?

I needed to use a hammer to tap one of the screws out which created some aluminum shavings. The same screw on the other side had the same problem. I carefully looked at the screws and they both had a slight bend to them. WTF? Grade 8 screws don’t bend easily.

The screws are 3/8” too long and the hole in the front is a problem

The screws are 3/8” too long and the hole in the front is a problem

The underlying issue is that the large fillet machined into the control arm doesn’t properly support the washer. When the factory tightened the nuts with an impact gun the washer slid towards the fillet, tilted and pulled the screw sideways. While this isn’t a big deal it deforms the screw, deforms the hole and exerts a shear force on the other screws.

In the picture above the hole doesn’t appear deformed, but in the picture below the screw’s threads have clearly been embossed into the side of the hole. The reason for this is that the screw was pulled towards the fillet as the nut was tightened.

The side of the hole facing the fillet has been embossed with the screw’s threads

The side of the hole facing the fillet has been embossed with the screw’s threads

I addressed this by using a 11/16” end mill to machine a 0.130” deep flat recess. While the other screws have 5/16” washers, I used an M8 washer for the recess because it has a slightly smaller OD. Because I had to remove/reinstall the control arms, fixture everything, locate the holes, etc. this took me hours to do and it’s something that Superlite could have machined in seconds. I can now sleep better tonight LOL

Recess machined and M8 washer in place

Recess machined and M8 washer in place

First Proof-Positive Problem

When I went to pull the engine to work on the serpentine system, I couldn’t attach the left lift bracket because the coolant expansion tank was in the way. That’s the first proof-positive problem that I’ve had! When the engine went in the engine compartment was naked, but now it’s full of stuff… so the problem demonstrates progress, right?

The solution was to cut the left lift bracket and drill a new hole for the clevis. This was a bit of a chore because they’re Kent-Moore J-41798 brackets which were used on the OEM assembly line and are made from 1/4’’ steel. They list for $500+, but you can find used ones on eBay for around $100. If you have an LS, I highly recommend that you pick up a set.

You simply remove the left-front and right-rear coil packs and attach each bracket with the provided bolts. There is no need to stuff rags between the chains and the engine because the brackets are stout enough to keep the chains clear of everything. That said, I do use a towel on top of the supercharger to prevent scratches while I’m connecting everything.

The engine can now be easily removed/installed without removing the coolant expansion tank. A big thanks to Ken who brought these to my attention.

The painted gray edge is the chop line

Serpentine System v1.0

The combination of the Daily Engineering dry sump and a remote electric water pump means that I need to completely redesign the serpentine system. The dry sump is located where the A/C compressor usually sits and it replaces the serpentine pulley behind the super damper with a cogged one. This means that the compressor needs to be moved to the other side of the engine. I knew that before I had the engine built.

However, I didn’t realize the impact of removing the mechanical water pump until I pulled the engine and removed the pump. In the picture below the automatic tensioner, idler and water pump pulleys are mounted to the water pump. I now understand why there are multiple companies offering direct-replacement electric water pumps. They replace the water pump pulley with an idler with the same OD and maintain all of the mounting holes. This means you can use the same belt and pullies without any engineering or fabrication. That said, I’m glad I went with the remote pump discussed in a previous post because it’s superior to direct-replacement pumps and it’s extremely easy to service. I’d have to pull the engine to service a direct-replacement pump.

I also learned that unlike the left side of the engine (right side when viewed from the front) which has three M10-1.5mm mounting holes, the right side has none.

Engine as delivered had a dry sump, a mechanical water pump and no provision for accessories

Engine as delivered had a dry sump, a mechanical water pump and no provision for accessories

The first step was to figure out the location of mounting holes; three on the block, four on the right head and five on the left head. I spent a lot of time looking for a simple dimensioned drawing to no avail. I found a CAD model of an entire LS3 on GrabCAD (I have an LS7 block, but the relevant mounting holes seem to be the same). After removing the accessories, the exhaust and the crank pulley, I was able to determine the location of the mounting holes relative to the crank. They seem to be accurate, but if anyone has actual dimensions I’d love to have them.

There will be three layers of belts, from back to front:

  • Dry sump: cogged belt

  • Supercharger: serpentine belt running on the super damper

  • A/C compressor and Alternator: serpentine belt running on a pulley mounted to the front of the super damper

I took a guess and laid everything out in SOLIDWORKS.

Left (supercharger belt in black and accessory belt in orange) and Right (base plate)

I designed three mounting plates:

  • Base Plate: spans the majority of the block, supports the other two plates and provides the rear mounting points for the compressor and alternator

  • Center Plate: replaces the mechanical water pump’s mounting points

  • Accessory Plate: supports the idler and provides the front mounting points for the compressor and alternator

I wanted to confirm the locations of the holes in the block and check the locations of the accessories so I laser cut plates from 1/4” plywood and 3D printed spacers in Onyx. Version 1.0 fit fairly well, but I need to tweak the location of the compressor and finalize the exact locations of the idlers and automatic tensioners.

Base and accessory plates; center plate not mocked… pretty naked without the water pump

All three plates installed

Spacers printed in Onyx for mocking purposes

I know that significant engineering goes into designing a proper serpentine system, but I only have a rudimentary understanding — watch the amount of wrap, tensioners go on the slack side, etc. — and I haven’t been able to find a resource that discusses serpentine design. If anyone knows of a good book, article, post, consultant, etc. please let me know.

I stumbled into Design IQ, a downloadable free program from Gates. The video below provides a quick overview.

As can be seen below, I entered the information for the accessory system into the application. It calculates the Effective Belt Length (top middle of black background) which is useful. It also calculates the wrap angle of each pulley, but I’m not sure if 259.26 degrees is too much for the drive pulley or if 47.93 degrees is too little for the tensioner. I’m also not sure how to orient the tensioner’s arc nor how to determine where to place its mounting holes so that it applies the correct amount of pretension to the belt while providing the maximum amount of adjustability. If anyone has any pointers, please let me know.

Accessory belt entered into Design IQ

Brake and Clutch Hard Lines Finished

The beautiful CNC-bent brake lines that came with the kit went in the trash. While the lines in the engine compartment were OK (until I changed everything), nothing in the front half of the car was even close to fitting and both the rear brake line and clutch line had unions in the middle of the side pod. This is the worst possible location for a union because a leak would go unnoticed and fixing it would require removing the spider. At this point, the only parts of the stock brake system that I’m using are the Tilton pedals and the upgraded Brembo GT calipers and rotors.

All of the hard lines are 3/16” stainless steel with 45-degree double flares. It would have been easier to use something softer than stainless steel, but IMO stainless is the most durable and looks the best. I wanted to use 37-degree single flares, but there has been some debate that they wouldn’t meet Department of Transportation (DOT) regulations. I asked around and read all of the DOT specs that I could find and I didn’t find a single mention of flares. However, I didn’t want to run the chance of getting into a debate with some inspector, so I went with the double flare which is a real pain in the ass on stainless steel. Nothing like spending hours bending the perfect line and then f’ing it up on the final flare! The solution to this problem is having the correct tool. If you’re going to do stainless double flares, you need the Eastwood Professional Brake Line and Flaring Tool:

That solved the lines. The next step was to figure out the best way to mount them. Several years ago I bought several different types of brake line mounting tabs and all of them developed surface rust. So I tweaked the nicest design by lowering the mounting hole so that the brake line would sit closer to the chassis and I Wazer’d a bunch out of 0.090” stainless steel.

Custom stainless steel mounting tabs

Custom stainless steel mounting tabs

I don’t like wrenching on brake lines when they’re not firmly fixed. I was unable to find mountable single or double stainless steel unions so I Wazer’d mounting tabs out of 0.090” stainless steel and had Abe weld stainless unions to them.

Custom single-union bracket

Custom double-union bracket and brake line mounting tab

Custom double-union bracket and brake line mounting tab

I used clamps from Made4You for the brake lines. They make single and double clamps for 3/16” line, but no triple clamps so I designed and 3D printed one.

3D-printed triple brake line clamp

The residual pressure valves (RPVs) that come with the brake kit are junk. I’m aware of builders that have had them leak, had them cause the brakes to drag and had the embossed flow arrow pointed the wrong way! They were replaced with ones from Wilwood.

Wilwood residual pressure valves

Rear brake split. The clip on the left will be finished the next time the oil reservoir is removed.

Rear bake line on the left, clutch line on the right and other rear brake line in the background

Rear bake line on the left, clutch line on the right and other rear brake line in the background

Paddle Shift System

To support paddle shifting I considered a standalone Gear Control Unit (GCU), but decided to upgrade my MoTeC ECU from a M130 to a M150 with GPRP because a single device simplifies wiring and provides tighter integration of fuel, ignition, throttle, and the shift actuator. An example configuration is shown below.

I considered MoTeC’s Paddle Shift Auxiliary Kit, but the solution from Shiftec is better. Their Air Power Source (APS) combines the relay, pump, pump-to-accumulator hose, accumulator and pressure sensor into a single motorsport-quality device. This increases reliability while reducing weight and complexity. There are only two connections; a -4 JIC for air and a motorsport connector for power and CAN communication. The pneumatic shift actuator is compact and seems well made.

Pneumatic Shift Servo and Air Power Source (APS)

The paddle shifters provide a fantastic tactile experience. I have always loved pushing buttons and flipping switches and these are the coolest switches I have ever used. I was playing with it in the garage and I was having so much fun I brought it upstairs. It didn’t take long for me to annoy everyone with constant clicking so I put it down. My son tired it and he was instantly addicted. My wife asked “What’s wrong with you two?” The best I could explain it was that it is was similar to the ridiculous way she acts around a cute baby — it’s just wired into our DNA.

The shifter’s body is anodized CNC aluminum, no surprises there. The lever actuates a micro switch which is rated for two million cycles. I’m not sure how many cycles my son and I have used so far, but if I don’t speed up the build I might have to replace the micro switch LOL.

There are no springs… so what type of sorcery is in the shifter?

The magic is simple, two high-strength magnets (I assume neodymium). Magnetic force is the inverse square with distance so it’s takes some force to break the magnets apart at which point the resistance disappears. When you release the tension in your fingers the billet lever exponentially accelerates and smashes into the billet body. This type of auditory and tactical experience wouldn’t be possible with a spring. I’ve driven a number of paddle shifted cars before (e.g., BMW, Porsche, Lamborghini, Ferrari, etc.) and their paddle shifters all feel like a game console in comparison. It’s a small thing, but it gives me a smile every time I use it.