S2's Build Thread

Scott

Lifetime Supporter
(Continued from previous post...)

I bought SKF Corvette Racing Hubs from TPS Motorsports with pre-installed ARP studs. According to their website:

The SKF Corvette Racing Hub unit is designed to provide high stiffness during cornering, thereby reducing piston knock-back and the need to tap the brakes (confidence tap). It has less than 10 micron run-out and is designed for durability and to maintain preload at sustained loads of 1.2g!
Six M12 - 1.75 mm thread x 75 mm Socket Head Cap Screws and six M12 washers are needed to mount the hubs to the uprights. I’m not sure what comes in the new kits, but McMaster only had that length in iron oxide so I spent a bunch of time looking for zinc-plated ones. The smallest quantity I found was a box of 80, so if anyone wants some PM me and I’ll ship six to you at cost.

I drilled the socket head cap screws so that I can add safety wires when the car is finished. The hub can be clocked in any of three orientations and I positioned it so that the wires would be as close as possible to the parking brake. This keeps them away from the primary brake caliper and enables me to run those wires with the electric parking brake wires. The reluctor wires are very close to the stub axle and there is no provision to keep them in place. I’ll figure out how to affix them once the parking brake brackets are machined.

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I wasn’t able to mount the upgraded Brembo GT two-piece rotors to the hubs because the holes machined in the rotor hat by Superlite have a very tight tolerance (a good thing). I assumed that the longer studs were slightly askew so I opened the holes a little. I found that that a 31/64” bit fit the holes perfectly, so I used one to locate each hole on a drill press. After clamping the rotor to the table, I used a 1/2” bit to open the hole and then a counter sink to chamfer the edge. While not a complicated process, I also chamfered the other side so in total that’s 20 hole locating and clamping operations, and 50 bit changes! I was able to get the rotor to fit by tapping it with my hand which caused the threads to create a few shavings. My bit set only goes to 1/2” so I’m going leave things tight for now.

I’m waiting for some parts to be plated (e.g., the ball joint plate, lower shock pins, etc.), so I haven’t mounted the hubs to the car yet, but I’m not expecting any issues.

Note that I didn’t upgrade the front uprights and hubs because, as discussed in a previous post, I had already upgraded the front hubs to re-buildable race hubs which are much nicer than the SKF racing hubs. Unfortunately they are no longer available.

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Ken Roberts

Supporter
I would have thought they would have gone directly to the C7 hub and 33 spline stub axle. Cheaper hub ($90) but still a X Tracker and with the larger/stronger 33 spline strength.

There is a guy on LS1tech selling a used set of the Hoosier rebuildable hubs if anyone else is interested in going this route.

https://ls1tech.com/forums/market/1935045
 
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I have the C7 hubs, just now have all the bits needed to install. interestingly I believe I am suffering the pad knock back that is mentioned in Ken's link about the Hoosier hubs. We'll see....
 

Scott

Lifetime Supporter
I would have thought they would have gone directly to the C7 hub and 33 spline stub axle. Cheaper hub ($90) but still a X Tracker and with the larger/stronger 33 spline strength.
I don’t know what drove Superlite’s decision, but the dynamics of their procurement process is obviously different than ours and you would also need to take into account the pricing and availability of the larger-spline-count stub axle.

I’ve been talking with Hill McCarty at Agile Automotive about a new transaxle and during that process we discussed hubs. Long ago they had made modifications to support the latest version of the C6 ZR1 wheel bearings. Although they have never had any play in the bearings they age them out every two years. So that’s about 10 events per year, several of which are 24+ hours with the car pulling 2 lateral g’s. That’s a lot more abuse than my car will ever see — well, other than some launches :)

Hill did point out that heat needs to be properly manged. While the aluminum upright does a pretty good job of wicking away heat so long as there is air flow, you need proper brake ducting if you’re pushing the car that hard.

With top-end C6 hubs the weak link is probably the CV joints. This is particularly true if you have a Graziano because the 4WD design, which is useless for a SL-C (at least so far), has asymmetric axles with the right axle being a good bit shorter. This puts more strain on the right-side CV joints.

There is a guy on LS1tech selling a used set of the Hoosier rebuildable hubs if anyone else is interested in going this route.
He description says it all Hoosier performance Hubs if you know you know "
 

Scott

Lifetime Supporter
There’s nothing wrong with the grumble of an American V8. I have a cobra with a 427 side-oiler, Webber carbs and side pipes. It sounds bad ass and I love it, but I want to do something a little different for the SL-C. I considered doing a 180-degree crossover exhaust, but there is no room to do it unless I cut through the top of the body which I don’t want to do. So, I was planning on a simple exhaust using the OEM exhaust manifolds because, according to my engine builder, custom headers may look cool, but they won’t generate any more power and will only lead to heat, fitment and leaking issues.

However, I keep looking at the 2-3/8” between the Daily dry sump and the bottom of the car. I considered lowering the engine to lower the center of gravity, but the supercharger snout and induction tube would hit the 2” x 6” chassis tube. If this were a pure race car, I’d notch the chassis and lower the engine, but for my use case that doesn’t make sense. It occurred to me that the space under the oil pan could be used for a 180-degree crossover exhaust.

While the original bundle of snakes increased power my fitment constraints may cost me some power (e.g., longer and skinnier primaries, increased number of bends, etc.), but I have excessive power so that’s not a concern. So why am I going to try and do it? For the sound. The sound of the Vette in the following video is bliss… please ignore the irresponsible driving.


That car has an LS7 with equal-length 36” long primaries. For fitment reasons the primaries are 1-3/4” and the collectors are flat. Round collectors, particularly when the primaries are sequenced to fire in a circular pattern (clockwise or counterclockwise), offer superior performance due to improved scavenging.

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I conceptually understood that two of the primaries from each side had to cross over, but how a double pulse on each side occurred and tube routing wasn’t intuitive to me. To get my brain wrapped around things I put together the following diagram which illustrates the exhaust pulses down the left and right cylinder banks for eleven compression strokes:

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Note that the stock exhaust creates a double pulse in each cylinder bank; the right during compression strokes 4 and 5 and the left during compression strokes 8 and 9. The 180 crossover exhaust crosses these primaries to the opposite bank which creates a symmetrical pulse down the left and right cylinder banks.

What do you buy for an 8-year old when a pandemic is looming? LEGOs of course. What do you buy a 50ish-year-old boy? Big-boy LEGOs. Specifically, a plastic LS7 engine block and an 1-7/8” icengineworks set to mock headers.

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The plastic blocks are attached to the exhaust flange using a block starter / tube adapter which are composed of pieces of rubber sandwiched between stainless steel disks. When the screw is tightened the rubber is compressed causing it to bulge. The large piece of rubber grips the inside of the exhaust tube and the small piece of rubber grips the plastic block.

I didn’t have short starter tubes tacked to the exhaust flange so I tried to insert the block starters directly into the exhaust manifold. That didn’t work because the exhaust ports are D shaped and the starter blocks are round. A little grinding was all that was required to get everything to fit. From left to right; front of starter block, rear of starter block and disassembled starter block with modified front plate and rubber.

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I had to drill a relief hole in the middle of exhaust port to accommodate the nutsert and screw on the backside of the tube starter. I subsequently realized that I had the flanges mounted upside down ;-)

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I’m not sure if I’ll be able get it to work out the way that I want, but it gives me something to do during the pandemic!
 
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Here's a flyby video of the 180deg headers. I think this gives a better sense for the dramatically different exhaust note.

 

Scott

Lifetime Supporter
Mason, I think that's the same car... and I agree that is sounds very different. Note that I have a typo in the exhaust comparison diagram. Compression #3 in the 180 Crossover column should be Left rather than Right.

I’ve been doing some additional research on 180-crossover exhausts, specifically on LS engines. While the C7 video in the last post has an LT and I have a LS7 my engine is a custom build and supercharged like the LT, so it hopefully provides some insight into what mine might sound like. In any event, that car has a build thread and I was able to determine how it was fabricated. As I previously mentioned, the optimal approach for scavenging and sound is a round collector with the tubes firing in a sequential clockwise or counterclockwise manner. As can be seen in the picture below the fabrication is top notch and flat collectors were used for fitment reasons.

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I was curious if the fabricator was able to optimally sequence both collectors. As can be seen below, the top collector is as good as you can get with a flat shape, but scavenging/sound won’t be optimal between B and C. The bottom collector has two discontinuities; B-C and D-A. Does it matter? Probably very little, but a round optimally-sequenced collector would likely sound a little more refined.

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Here’s another video of that car. The first 30 seconds has an x pipe and the following 30 seconds has no merging after the collectors. The owner preferred the version without the x pipe so that part of the exhaust went in the recycle bin. Interestingly, Abe fabricated and installed an x pipe in a Ferrari 812 Superfast last week and everyone preferred that sound.


The following picture shows the version with the x -pipe.

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Here are a couple of other video/sound clips. All of the cars are white and I’m fairly sure they’re all the same car. In any event, they provide some inspiration.


 

Scott

Lifetime Supporter
The back ordered clamshell couplers and ferrules arrived and Abe was able to get most of them welded, but I’m still waiting on the XRP PROPlus hose and crimp collars.

The swirl pot is finished. The two -12 inlets on the top left connect to flex hose, the -24 outlet on the bottom right connects directly to the 1-1/2” stainless steel tube that runs down the side pod and the two threaded bungs on the middle left attach to a chassis bracket.

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The radiator inlet and outlet are connected to the 1-1/2” stainless steel tubes via -24 hose and clamshell connectors.

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Right side, the radiator weld ferrule is just tacked

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Left Side

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1-1/2” stainless steel tube, weld ferrule, clamshell coupler and hose end

The next step is to finish the welding the tubes in the engine compartment and fabricate the flex lines once the parts arrive.
 

Scott

Lifetime Supporter
I copied a coolant expansion tank that was designed by some early SL-C builders (Mesa, Howard and Will) and I made the following changes:
  • The engine steam and radiator bleed connections were moved from the bottom to the top of the tank to improve deaeration (i.e., air bubbles and steam don't need to percolate through the liquid).
  • The mounting flange was replaced by four aluminum spacers that provide a 1/4” air gap between the tank and the firewall to reduce heat transfer into the cockpit. To accommodate this, the tank is 1/4” thinner.
  • A sight tube was added.
  • The hose barbs were replaced with female ORB weld bungs. This allows a wide range of fittings to be used (e.g., AN fittings, hose barb, etc.) which means that I can change my mind on how things are plumbed.
  • A bung was added to the bottom of thank for the swirl pot bleed line.
  • The aluminum thickness was increased from 0.093" 5052 aluminum to 0.125". A little thicker than necessary, but I never wanted to have an issue.
  • A baffle was added to reduce coolant sloshing. This, combined with the thicker aluminum, will prevent the rear from bulging when pressurized as observed by several owners of the gen-1 tanks.
I modeled the tank using the sheet metal features in SOLIDWORKS. The aluminum pieces were designed to have a 50% (i.e., 0.0625”) overlap to provide perfect corner weld joint. It looks good in CAD, but time will tell if it comes out as planned ;-)

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It took a little while for me to figure out the sheet metal features, but that effort was rewarded because SOLIDWORKS generates the flat patterns and bend lines to form the shape. This takes into account the type and thickness of the material, the bend angle, roll radius, etc. The image below shows the shape and three bend lines to form the top.

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Design looks good Scott, Though I would prefer the fasteners not be along the roof line for aesthetic reasons.

Are you going to have the plates waterjet cut on your WAZER?
 

Scott

Lifetime Supporter
Mason,

I take your point on not putting the standoffs on top for appearances. I was trying to keep them away from the hoses. Keep in mind that the entire curved top is tucked under the spider and the cap just clears the edge of the fiberglass so I don't think they'll be visible. That said, I'll finalize their position once the box is welded.

I could fabricate a tank just as nice as that one in my garage... well, other than the whole welding thing LOL
 
Hey! There is some intellectual property infringement happening here ;)
Realistically, those mounting posts will never be seen. As pointed out, they will be obscured under the spyder clam shell.
BTW- what do the (don't call them PINK) pink collars do?
 

Scott

Lifetime Supporter
Hey! There is some intellectual property infringement happening here ;)
Mesa, you were attributed and the royalty check is in the mail ;-)

I'm not sure if you're asking what they are in general or those specific ones. In general, they are Adel Wiggins clamshell couplings. I used a -64 AN one on the intake tube and wrote about them in post #426. They were originally built for aerospace (ratings are in psi and psig, pressure related to a vacuum --- as in space). They are amazingly well engineeed for critical applications; they tolerate axial displacement and angular misalignment, are self locking, etc. They use them on spacecraft, to connect fuel tanks on jets, in motorsport from F1 down to garage monkeys like me. I bought them because they're pretty -- I mean I can quickly connect/disconnect them with one hand and no tools. There are lots of knockoffs so beware what you use on anything critical. This guy has definitely had his man card revoked.
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I was looking for a good video and apparently Earl's sells proprietary crimp-style hose ends that can be connected with a Wiggen's coupler. They don't feature the same internal sleeve, but the video does a good job showing how easy it is to connect and disconnect them.


If you were asking about the ones pictured in the prior thread, they are for the radiator supply/return lines. They have a weld ferrule on one side and a crimpable hose end on the other side. The flex hose is backordered.
 
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Scott

Lifetime Supporter
I’m working with Andrew from Aeroworks Performance to fabricate some body parts. He has extensive experience using 3D printing to create composite aero parts. Depending on the situation he either prints a female mold, a male buck or the actual part. He built a 3D printer with a 27” L x 13” W x 14” H print size and he’s planning one that’s capable of printing a splitter as a single piece. For now, he glues pieces together.

I want my first rodeo to be a small one so first up are the brake ducts and radiator outlet. The primary reason for enlarging the brake duct openings is to increase airflow to heat exchangers located on the left and right of the radiator while also feeding a brake duct. I also think that the modification improves the look of the car.

Kevin designed two shapes, angled and rounded, each with a narrow and wide variant. The narrow angled version (A1) is the same as what Allan has done on a bunch of cars. I’m still in negotiations with his licensing department, but so far he’s a tougher negotiator than Mesa… LOL.

IMO the angled versions are more aggressive and modern. The rounded version is less aggressive and more in keeping with the the curves found elsewhere on the car. Thoughts?

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