'70 Nova LSX swap LY6/TH400

[entropy]

Originally Posted by TheBandit

I haven't had time to put a real video together yet, but I made a big change to the Nova over the last few months.

Here's a teaser:


As I find time, I will put some photos and tech info together to update the thread. I haven't kept up on forums like I used to!

I hope everyone is well. How are you folks connecting these days? There's been hardly any activity here in months.

The OFN still ROCKS!

E

[TheBandit]

When people are on here contributing it can be amazing! I really want to share the metal work I did on the tunnel as soon as time allows. It was my first time with a bead roller and I had a great time learning. I thought a lot about Jaysin (RIP) as I was working on it and how much he and others here have influenced me over the years.

[Graham08]

Nice work on the video editing!

I've been following along on Instagram, but it will be nice to get a little more depth here. You're going to have to change the thread title now that you've done a TH400 delete.

[Rock4XFab]

I can't remember that last time I was here, but life has gotten in the way. I have been making a lot of really cool fixtures and Robotic welds along with setting up new weld cells

[Graham08]

Originally Posted by Rock4XFab

I can't remember that last time I was here, but life has gotten in the way. I have been making a lot of really cool fixtures and Robotic welds along with setting up new weld cells

Hey there! We haven't heard from you in forever...sounds like you have some cool stuff going on.

[Rock4XFab]

Yep, it has been a while. Some robotic welding 1/4 wall tube to 5/16 plate

[TheBandit]

Originally Posted by Graham08

Nice work on the video editing!

I've been following along on Instagram, but it will be nice to get a little more depth here. You're going to have to change the thread title now that you've done a TH400 delete.

Thank you! I'm currently investing in more serious camera gear with plans to do car cinema/shorts as a hobby, along with capturing my family's travel adventures. I bought a drone at the end of last year and put this one together with a friend outside of Phoenix:



The problem with that video is while it has some interesting footage, I wasn't able to tell any kind of story with it. It's also missing close and mid shots. There's no climax or action. The overall feel is sort of slow and sleepy. But I learned a lot about my drone and editing. I will work to improve!

[Graham08]

Originally Posted by TheBandit

Thank you! I'm currently investing in more serious camera gear with plans to do car cinema/shorts as a hobby, along with capturing my family's travel adventures. I bought a drone at the end of last year and put this one together with a friend outside of Phoenix:



The problem with that video is while it has some interesting footage, I wasn't able to tell any kind of story with it. It's also missing close and mid shots. There's no climax or action. The overall feel is sort of slow and sleepy. But I learned a lot about my drone and editing. I will work to improve!

While I'm sure you're going to be critical of your own work (I know I am!) I think that is quite the video! You have some skills! I like the backing track on this one...is it the Mermen?

Pretty cool that you keep moving forward and into different stuff!

[TheBandit]

Thanks for the kind feedback. It is true we are our own worst critics. But it is good to learn and identify areas for improvement too.

I can't recall the artist for that track - I pulled it from a YouTube audio library, so it's probably not a well known artist. Choosing the right background track is a tough job - it really sets the mood and pace of the video.

My favorite part of this video is the intro sequence. The audio of the car driving up was taken a coupe hours after I took the video footage. I stood at the side of the road with my microphone and had him drive by from about 1/4 mile away. I also took engine sounds of him idling and driving with the microphone taped onto different parts of his car. It was really cool to piece the audio together with the footage and make it seem convincing. I also shot the opening wide shots well before he arrived on site. I just happened to catch a couple cars crossing in front of me, which made for cool opening footage.

[TheBandit]

Videos are cool but they take a while to edit and I am still a forum junky, so I'm going to try for a text & photo update to get this thread up to speed.

Subframe Connectors

If you haven't seen the part 1 video of my subframe connector install, there's a lot more info there to complement what I'm going to type here, but since I haven't found the time yet to edit part 2, I'll go ahead show some start to finish photos of the install.

Installing weld-in subframe connectors requires access to the floor pans so I stripped out the interior, revealing rust areas I haven't looked at since around 2004. Way back then I wire wheeled the floor and put a coat of Rustoleum "rust stop" primer over everything. I called Rustoleum at the time and confirmed it could be left as a top coat. Over 15 years later I am not unhappy with how this held, but it's certainly no panacea for rust. Things have gotten a little worse, most likely from time periods I had the car stored outside with water leaking through pretty much every window on the car. The passenger side is the worst, with pin holes and very thin areas right around where he subframe connectors needed to be installed.



I decided to give installation a shot anyway and see how things would go, knowing I can drop in new floor pans or patch in areas later if it didn't work out. So one of the first steps was positioning the cut templates under the car and tracing out a cut path. They are positioned based on where the weld seam is along the side of the car along with a distance from the subframe connector. In hindsight using the seam as a reference was not the best idea; it's not exactly straight. I'll explain more further down.



I cut the floor using a 4.5" angle grinder and a cutoff wheel.*Peek-a-boo!



I was happy at first to find the connector was fairly tightly fitting on either side, but as a looked around I discovered a few fitment issues which I could have avoided. First in the photo just below you can see there is some gap at the back of the connector. I later trimmed a bit more so it would slide back further and meet the "frame" at the back of the car.



The other major issue was the left-right alignment did not match up with the rear frame. This is probably a direct result of using a generic reference dimension DSE provided from the weld seam to position the cut template. All I had to do to avoid this when I installed the other side was to measure my car myself and position the template left-to-right based on references from my own car rather than the provided dimension. Lesson learned. Ultimately I corrected this by trimming more of the floor away, but that did leave some gaps which were difficult to weld.



The other area of fitment that is imperfect is back where the notch of the subframe connector wraps around the existing floorpan structure to meet the frame. This notch is needed to angle the connector into place, but it leaves 1/4-3/8 gap area. When I called DSE they said they just fill weld this gap, but given how thin the sheet metal is I plan to make a small plate to fill this area before welding. This is one area I have currently left unfinished because to fully weld around the back of the connector I need to remove the leaf spring perch and get some fuel and brake lines out of the way. I will come back to this soon as I have a few other things I need to do under the car around the same time.



Lastly the front of the opening had a very sizeable gap with the top of the subframe connector. Luckily this was very easy to remedy with a hammer. A few strikes and I was able to bring the sheet metal down to the top of the connector before welding.



Once I had the connector fitted, the first thing to weld was the end cap at the front of the subframe connector. I should mention fitment involved trimming the front of the connector back by about 1/2in, which provided more room for installing and room for this end cap so the connector didn't interfere with the subframe. It was a happy moment for me to be welding on the car again, since the last time I did any significant welding was when I narrowed my rearend a few years ago. I'm not sure why I decided to weld in shorts - it was probably pretty hot at the time since this was toward the end of Summer 2020.





With the end cap welded and cleaned up, I fit, clamped, and tack welded the front brackets with the connectors in the car. One thing you may notice in this photo is the shape of the brackets has a little notch at the top where they meet the subframe. On this side I left it as shown, but I realized when installing the other side that it fit better and I could get more weld length if I just cut that little notch off and had a simple diagonal along the entire front.



After those were tacked I took the connectors over to the bench and made some of the most satisfying welds I've personally ever made. For sure the are not perfect, but I am really proud of these.







Once that was done, I went on to more challenging welding in the car. I used a jack to keep the connector flush against the floor crossmembers before tacking everything into place. Then I went to town welding all the thicker materials like the front and rear connections with the frame and where the connectors met the floor crossemember.





All along the most concerning area for me was welding the floor pan sheet metal to the connectors. The sheet was likely around 20awg originally, but many areas were thin due to rust and there were a few gappy areas too. To make matters worse I needed to weld thick to thin and I have very little experience with sheet metal welding. So before I did anything on the car, I cut cards out of the floorpan remnants, cleaned up the edges, and did a bunch of practice welding at the bench. At first I tried a series of small tack welds. This did not work well for me - either the welds came out too cold or if I turned up the heat they just burned right through. You can see just how bad the metal was from the passenger side in these photos



Eventually I settled on a method using stitch welding. As I welded I focused the wire on the thicker material and just periodically dipped the puddle down to the sheet, moving my wire in a "J" shape, to connect it. This worked much better and I was able to weld roughly 1-1.5" lengths without burning through. This required the heat to be just a tad lower than what I normally would use for the thicker material. I had to really concentrate on the edge of the puddle here - as soon as it connected with the sheet I had to redirect the wire toward the thicker material.



Welding on the bench and welding in the car were not exactly the same. On the passenger side (shown below) the metal was terribly thin and would burn through easily. But the main problem was that along the sides of the connector the floor had a rib depression creating a crevice to weld down into. This made it hard to keep the wire stickout length short or aim it at the side of the connector. It felt like I was welding cotton candy and I was honestly struggling all the way around. I had to take it very slow and do a lot of filing, chasing crap thin metal around and refilling as I hit thicker stuff. This section of sheet needs to be cut out and replaced, but I did not want this project to snowball so I did my best to make it work. The finished product leaves a lot to be desired, but I don't think it's of structural concern. I plan to replace the pans when I strip the car for paint (some day)

When I did the driver's side, I made some major improvements by hammering the sheet metal flat so I wasn't welding down into a crevice. Plus the metal was mostly free of rust damage so my job was much easier there.



The last step to getting back on the road was cleaning and laying a coat of self-etching primer to protect the metal.



Then I spray bombed the underside black, except a masked off section at the rear where I still have some finishing work to do.



That brings things up to speed on the subframe connectors. They are not done done, but they are mostly done. At a later date, I will finish weld the rear areas I could not access, and refinish the interior floors + seam seal. All in all I am happy with how they turned out and I definitely like how low profile & integrated they are under the car. DSE makes a good product. Bolt-in connectors would be much easier but I think the integration of these is worth the admittedly high effort.
*

[Graham08]

Nice work on the subframe connectors...including documenting how you improved the process on the driver's side. You're right about the weld-in version being a much better way to go than bolt-on version. They look much better since they don't hang down below the car so far, and tying them into the sheet metal helps rigidity, too.

My opinion is that getting a good stiff foundation to work from will only help as you tune the car's handling for autocrosses and track days.

[TheBandit]

Thank you Graham! Experience really helped on the driver's side. I hope these will prevent any long term damage to the body and give a solid foundation for suspension tuning as I get more into that.

6 Speed Manual Swap

For years and years, I've been wearing away at Mrs. TheBandit with the objective of replacing the TH400 with a manual 6 speed. The cost of a transmission swap can be as much as an engine swap, depending on how you go about things, and I knew the way I wanted to do it would have a considerable financial impact. Mrs. TheBandit has always been supportive of my car hobby and she helps keep me honest and make sure we're putting money in the right places first, like retirement, college savings, etc. We are fortunate to have good income but we don't use that as an excuse and we approach all our big purchases thoughtfully. The time finally came last summer: for my birthday she wrapped up a printout image of a transmission, giving me the green light to make one of my hotrod dreams a reality!

After the green light, researched options intensely, calling different vendors and friends before deciding on an approach. You can skip the following if you're not interested in my thought process on parts/vendor selection :)

The obvious transmission candidate was the Tremec Magnum, but a friend alerted me that the standard Magnum's rearmost shifter position was about 3" forward of where a 4th Gen F-body T56 shifter was located. He had used both transmissions in different 1st gen Camaros and was really frustrated by the forward shifter position on the Magnum. I measured from my bellhousing surface to the firewall, then from the firewall back to where the shifter would be and decided the standard Magnum shifter position was not where I wanted it. This lead to the discovery that Tremec had recently released a new variant, the Magnum-F, which had the same shift location as the 4th gen F-body T56. Compared with the standard Magnum, the disadvantages of the Magnum-F were (1) more cutting required due to the extra length and (2) no mechanical speedometer drive. The Magnum-F shifter position was much more to my liking, so I chose the Magnum-F for my swap. Furthermore, I had the choice of a wide ratio or close ratio gearset. I ran a few calculators and decided the close ratio would work best with my rear gear ratio of 3.73 and tire height of 25.4in. The problem with the wide ratio is the first gear was just too low to be useful without regearing the rear and I didn't feel like the wide spread would offer the "right" ratio selection at lower speeds for the types of autocross courses I do, even if I swapped rear gear ratios. Some conversations with other autocrossers/pro touring folks confirmed the close ratio is generally preferred. Keep in mind this was before Tremec announced the new TKX 5 speed transmission, which may have been a contender if it were available at the time I was looking. The TKX is shorter and does not have the same gear selection as the Magnums, but likely will require less or no cutting to install.

Another important choice was how to approach the clutch hydraulic system. There are a few ways to mount a clutch master in these applications. One of the most common is to use a simple bent bracket hanging off the brake master/booster studs, which will accept an OEM 4th gen F-body master or can be adapted for aftermarket masters from Tilton or Wilwood. DSE and several companies offer variants of this type of bracket. I did not like this method because it leaves a relatively open hole in the firewall and I wanted to use an aftermarket master in case I wanted to change sizes down the road. Another option is a tilting/adjustable mount. American Powertrain offers a version of this. I looked at this option seriously but it also did not have a good way to seal off the firewall. Ultimately the option I landed on is the Silver Sport Transmissions (formerly Keisler) billet mounting system for Wilwood master cylinders. I liked the design of this system because it seals off the firewall and allows use of a Wilwood master.

The next option was transmission crossmember. I looked at quite a few options. One of my friends had some issues with his transmission bouncing using a simple tube type crossmember, so my preference was to use some kind of boxed design. I really like the boxed high clearance design of the Hooker crossmember, but ultimately landed on the Silver Sport crossmember for the benefit of getting everything through one source.

Speaking of Silver Sport, one of the best decisions I made for this project was sourcing the transmission and most swap components from Silver Sport Transmissions. Their customer service is beyond stellar. Every time I had a question or issue, they were quick to answer the phone and offer solutions, parts, etc. I'll give some examples as I go along in this thread. Let's get on with the build...

First up, the "big day" arrived last August when my pallet showed up on the promised delivery date. In this stack of boxes is nearly all the hardware I needed to put the transmission into the car: the transmission, bellhousing, pedal assembly, clutch hydraulics, crossmember, bellhousing alignment fixture, and hardware. Hardware is one of those little things that can really add up, both in the cost of individual fasteners and the many trips back and forth to the hardware store. Silver Sport itemized EVERYTHING - I don't think I had to go to the hardware store once for a fastener related to this swap.




Of course I had to open things up and play racecar simulator right away!



My TH400 was so excited it peed itself. It was nice to see the fluid drained clear and it will be ready for a new home.





Out with the old.





With the old transmission and flex plate out of the way, I got to work installing the flywheel and bellhousing so I could check alignment. I also installed the pilot bearing and posted this photo to my Instagram account.



See something wrong? No? Did you look really closely at the photo? I sure didn't. But Jeff Kaufman at Silver Sport Transmissions apparently did, because soon after I posted this photo he reached out to let me know my pilot bearing was installed backwards! There is a radius entry on one side that is supposed to face the transmission to help with shaft alignment during installation. No worries - I got the right tool for removing the pilot bearing and popped a new one in the right direction. Important note: there is a press-in plug in the back of the LS crank that can get dislodged if you try to use the bread trick to remove the pilot bearing. If that happens you can have a nasty oil leak that will get all over your clutch, so borrow or buy the right tool if you can.



Checking bellhousing alignment is a very important step. Any kind of side load on the input shaft can cause poor/difficult shifting and premature wear. Using the gauge plate provided by Silver Sport, I found my runout was out of spec: the total indicated runout was 0.015in, meaning the center of the transmission was offset by 0.0075in.



To correct this, I bought a set of 0.007in offset dowel pins from RobbMc Performance. This guy was very friendly on the phone and got the pins out to me quickly. Important note: to install these dowel pins for use with a cast aluminum bellhousing, you must cut down the length so they do not bottom into the bellhousing.



The LSx dowel pins install in open holes in the bellhousing. I tried a hammer from the backside to pop them out, but they didn't budge. So I got to work making a tool to pop them out. I welded a bolt onto the foot of a c-clamp and put a socket over the dowel so I could press the old dowel pin out of the block.



Unfortunately that did not go so well on the first attempt.



I grabbed another c-clamp and welded some reinforcement onto it for another try.



This time it worked perfectly and I was able to get both original dowel pins out of the block.



With the new offset dowels installed, the total runout measured less than 0.001in, meaning the bellhousing has less than 0.0005in centerline offset. To be honest that is probably well within the noise of what can be measured effectively with a gauge plate. Time to install the infinitely variable torque converter:



Clutch selection was tough, because there are tons of options and always lovers and haters of every brand and type. After driving a friend's high powered turbo LS Camaro with a Magnum and Monster twin disc setup, I was really tempted to put a twin disc in my Nova, because the pedal feel was so light and easy. But I don't have the power to warrant the cost of a twin disc setup. I also considered the LS7 clutch setup which is a very popular candidate, but didn't like the idea of the weight or the self adjusting system it has which apparently causes issues for some (not many!) people. Ultimately I concluded that you can't go terribly wrong with any of the major clutch manufacturers. I decided on a Monster Stage 2 with a 28lb flywheel, because it was rated to my torque requirements and generally had positive reviews. Having driven the car now, I am happy with my choice - pedal feel is only moderately stiffer than stock application clutches I've used in other cars and it has a good transition.

The next important measurement to check was the clearance between the throwout bearing and the clutch fingers. This is a critical measurement, because if this clearance is too great, the clutch may not fully release. If it's too tight, the clutch may not fully clamp. Either situation is bad. Silver Sport provided shims to get the spacing just right. I used straight edges to measure and ended up with a clearance of 1/8" which is in specification.



Now we get to the REAL FUN - open heart surgery on the floorpan! This big ol' 6 speed transmission most certainly would not fit without making some room. Another advantage of working with Silver Sport is they have a library of cutting templates for many car and transmission applications, some involving just minor cuts here and there, others requiring a bit more space. In my case I used a template intended for a standard Magnum transmission, as a starting point for my longer Magnum-F. I started by establishing a centerline for the template, measuring from the A and B pillar areas to find the center of the tunnel and extending that line using a laser level.



Then I taped the template down and marked out my cut area





My choice of surgical instrument was my trusty angle grinder and cutoff wheel. Minutes later, here's Johnny!



Once the bulk of the cut was made, I took a few additional measurements from the bellhousing and transmission and extended the cut back a little bit to make room for the longer Magnum-F. This meant cutting directly through one of the integrated floor crossmembers, but don't worry - I will show you how that is addressed later on. I will also mention at this point that I later extended this cut even further back to make room to transition the tunnel... but for now this is about the minimum cutting needed to fit the Magnum-F into my car.



It was time...









That's as much as I have time to write-up for today. I will continue the update soon.

[Graham08]

Thanks for posting this up, Clint! I've been following along on Instagram, but it's nice to see the additional photos and commentary. That is so cool that Silver Sport had a template to at least get you close on the floor opening. That had to save a ton of head scratching and incremental trimming to get to the final opening.

[TheBandit]

Originally Posted by Graham08

Thanks for posting this up, Clint! I've been following along on Instagram, but it's nice to see the additional photos and commentary. That is so cool that Silver Sport had a template to at least get you close on the floor opening. That had to save a ton of head scratching and incremental trimming to get to the final opening.

Thanks for reading along! I can go into a lot more depth here and I agree it's much better to have the explanations and string of photos than just a single photo with a short caption! The template was very helpful because it gave me confidence that I'd have the right cut and I spent almost no time iterating.

Continuing with the update....

One thing I noticed when my transmission parts arrived is that the transmission crossmember was a different design than what I had seen Silver Sport use on another Nova. I called and confirmed they had recently implemented a more universal/adjustable version. Unfortunately this new version was not a good fit - the mounting area of the crossmember was several inches lower than their original design and blocked exhaust routing.



A quick phone call and Silver Sport offered to rush ship a new crossmember using their older application-specific design. This gained a few inches of clearance which was plenty for my 3" exhaust routing.






Next, I installed the STX short throw shifter. This included a bronze bushing to replace the factory plastic one in the shift rail. I used Loctite bearing retainer to keep it in place.



At this point I decided to reinstall my driver's seat and mock up shift lever options. Knob position and lever length affect driver's arm position, reach, and throw, so I think this is an important thing to get right for the specific car, driver, and seat position. For mockup, I used vice grips, some flat bar, a long bolt, and a shift knob. This allowed me to shift through all the gears and choose what worked best for me. It's worth noting I am 6' tall with a 32in inseam.






The 8in levers were comfortable, but the length and longer throw made it feel more like a semi truck compared with the throw and height of the 6in levers. In spite of the shifter being 3" further back with the Magnum-F trans, I still found the straight levers resulted in extended reach in forward shifter positions. With the laid back levers, my elbow was just slightly bent for comfort and overall I preferred the 6in laid back shifter over the other options. So I shopped around for a lever and found I really liked the Hurst billet levers that were released last year.



I highly recommend mocking up parts like this or trying other people's cars, because it makes a bigger difference than I previously realized. Fitting the car to my personal ergonomic needs has made it a lot more enjoyable. That was true when I lowered my seat height, adjusted my shoulder harness tether length, and now with the shifter position. The car is a joy to drive.

[TheBandit]

Tunnel Fabrication

I've always thought of my car as a vehicle (pun?) for lifelong learning. I take on projects to challenge my knowledge, skills, and experience. That's why I often do things the "hard way" - the resulting personal growth is always a payoff, even if the results on the car aren't perfect. Yes it can be frustrating - failure is frustrating - but it has always been worth it!* Swapping this big transmission into the car was another great opportunity to learn and stretch myself, especially with the need to build a transmission tunnel.

To start the tunnel replacement project, I cut and bent a 1" wide piece of 20awg sheet metal to serve as a profile template. I wanted the resulting tunnel shape to be flat at the top with a radius along the edge, so I went through my collection of random pieces of pipe and wood until I found a piece of a closet dowel which made a bend profile I liked. I could use the same pieces of dowel later to form the tunnel. I made several versions of this profile with different dimensions before I decided on this particular one. To make sure it sat level and centered in the tunnel, I marked the centerline, equal distance bend lines, and equal distance cut/alignment lines so all I had to do was line things up in tunnel opening to get it centered and level. To get the right height, I started out with a longer-than-needed profile, laid a long straight ruler from the shifter to the profile, and moved it up and down until I liked it, marked an alignment line on one side, then carefully measured and reproduced the alignment line on the other side. I used basic spring clamps to position it as I made adjustments, then once I was happy I drilled a hole through each side and installed a Cleco clamp. This was my first ever project using Clecos and they are absolutely awesome!





Next I needed a template to get the right shape for my first piece of sheet metal. It tried taping some light poster board over the opening, but it did not want to comform to the shape very well, so I ultimately used a bunch of painters tape instead. I laid strips between my profile and the original tunnel, eventually building up the needed shape.



I quickly found there was no way I could fit a marker inside the tunnel to mark out an accurate edge for my template. That's when a little brainstorming paid off. I grabbed my Xacto knife and used that to cut against the edge of the tunnel, creating a perfect template of the right shape!



I carefully transferred my masking tape template onto a piece of poster board so the edges would not end up sticking together. Then I traced that template onto a piece of sheet metal. It's worth noting that before I even cut the masking tape out of the car, I made match marks at the center of my profile template and the car so could line things up later - I transferred those alignment lines to the sheet metal as well. Finally I drew out flanges that would later serve to overlap the existing tunnel for future welding.



I cut this piece out using a combination of electric shears for most of it and hand shears for a few detail areas. Then I slowly, incrementally bend the piece by hand from the center out until I had a decent fit in the car. This involved going back and forth to my closet dowel and carefully connecting the radiuses of my profile back to the corners where the piece meets up with the original tunnel/firewall area. I did this incrementally and it involved dozens of trips to the car to check fitment, then back to the workbench where I hand belt the piece over various random objects.



The piece was starting to look good, so it was time to bring out one of my favorite new tools:



This is an Eastwood 19" bead roller. I have been wanting a bead roller for more than 15 years, but I could never justify the expense. This project was just what I needed and I am SO GLAD I picked this thing up. I modified the bead roller by attaching my old Grant steering wheel using a 1" set-screw shaft collar welded to the back of the wheel. Here is a quick video review for anyone interested:



For this first piece I used the bead roller three different ways:
1) I installed the polyurethane lower die with an offset/flange upper die and "tipped" the front edge of the piece to make the angled flange that follows the front of the tunnel. This was was a little tough because adding this flange caused the material to straighten out, so I had to reform it a few times until it stretched enough to keep the* both the curve of the tunnel and the flange I needed for attachment.
2) With the offset dies, I added flanges along the bottom left/right edges of the piece. This was very straight forward, but I should note I also followed up with the polyurethane lower die so I could tip an angle into the flanges.
3) With the smallest beading die, I added partial beads on either side that meet up with the original tunnel beads from the factory.

Here is how the pieces turned out. I was really stoked!





Now it was time to create the rear profile to establish the shape of the main section of the tunnel. Once again I cut a 1" wide strip of sheet metal, measured center line and bend locations, and adjusted the height using a long ruler until I found just the right shape and position. I narrowed the profile of my bent piece about the same amount as the narrowing of the tunnel open, so when viewed from the top the entire tunnel would taper toward the rear.



For this template I decided to try poster board again. To be honest this did not work the best. The poster board I was using was just a bit too thick to establish the bend at the top edge. You can see in the photos it's a bit deformed, which later meant the metal wasn't a perfect match, however because I used overlapping pieces it did not make any difference to the final fitment.





Here is where thoughtful planning and patience came in. I've learned over many projects sometimes I have to remind myself to slow down and take the time to think a project through. When doing layout, it's imperative to get your mind in the right place and even step away and come back to check over or adjust your work. Below is the layout I put together for making this section of the transmission on a sheet of 20awg steel. You can get a sense of how much thought I put into laying out the bends, cuts, flanges, and beading paths. I labeled areas that would become bends, bends or flanges and I also cross hatched the areas I intended to cut out to avoid mistakes. This took a lot of time with a few good rulers. I can't stress enough how important a good layout is and you'll see how that translated into the finished product further in this post



Here's a video screengrab of cutting out this piece. I have to say, electric shears are AWESOME. This was my first project using a set and it's so so much better than using a jigsaw or hand shears. The metal does not deform at all and it cuts quickly. It's also very easy to line the edges of the shears up to cut lines for a very accurate cut. Electric sheers, step bits, Clecos, punches, and bead rollers are now my favorite sheet metal tools!



Once the piece was cut out, I used offset dies in my bead roller to make panel reliefs. All I had to do was carefully follow my layout lines. I did this in a single pass on the bead roller and most of my lines met up well. I could point out some of the faults, but most people would never notice. The best thing about these reliefs is they did not distort the panel whatsoever.





Next it was time to form the radius edges. The right tool for this would be some kind of a sheet metal brake. A magnetic brake would be my choice if I had unlimited funds, but I learned a long time ago you can do a lot with just your hands and a few random objects & clamps. Here I am using closet dowel as my bend radius, a 2x4 to keep the dowel reasonably held down, a pair of clamps to hold it to the workbench, and my hand/knee to bend the sheet metal as I supported the dowel with my other hand. I worked along the edge back and forth and checked the bend angle with a simple protractor until I had a consistent bend from side to side.



I cut a quick and dirty hole for the shifter to poke through, then ran it to the car to check fitment.



WOW! I had envisioned something like this, but seeing it in sheet metal just blew my mind. I could not believe I made this myself. Back to the bead roller to add & top flanges and a bead...







You can see my goal was to match the factory floorpan bead and carry it over the top and have a flange along the edge for overlapping & welding.





At this point I felt the fitment was close enough that I could cut out my two access areas and see what they looked like. I also began adding Clecos to "suck" the pieces together and keep things in position. Each of these cutout areas serve a purpose. The rear one is long with lots of room behind the shifter so that I can lift the transmission completely into position before sliding the transmission shaft forward through the clutch as I mate it to the engine. The front cutout makes it easy to reach my hand in to access bell housing bolts. I found both of these very helpful when R&Ring the transmissions at various stages of mockup.





With a few more Clecos, here is how the transmision tunnel was shaping up

[TheBandit]

At this point I had built enough of the tunnel to pull the transmission back out for the remainder of the work. I decided it was important to pull the trans so I could have full access inside to check fitment and eventually paint. The access holes came in very handy for getting to the more difficult bellhousing bolts at the top passenger side of the transmission!



At this point I decided to extend the tunnel cut quite a bit so I would have room to transition the new tunnel back to the original floorpan.



For the final section of the tunnel, I elected once again to use painters tape to establish template and cut with an Xacto knife. Again I marked the tape with centerlines so I could match up dimensions later on.



I transferred the cut masking tape to a recycled piece of poster board that I used for the previous template.



Next I measured and laid out my pattern. I used a large socket to mark out the corner radius I would use for a beading path.



Here is what the flat piece looked like when I did a rough check in the car. Laying it in position helped me eyeball where it would need to be bent. Notice that the front of the piece would need to remain flat while the rear of the piece would need to curve over the existing tunel.



Before doing any forming, I used offset dies to make a relief area in the panel. This is mostly for cosmetic purposes to echo the design of the other tunnel section, but it also stiffens the panel quite a bit.



Then it was time to start forming the part. I try to form from the center outward because any changes at the center of the panel have a big effect at the edges of the panel. I wanted to get the center correct before I try doing the outside features. For this I used a piece of 3" exhaust pipe and I concentrated my hands at just the rear part of the panel, trying to maintain the straight/flat profile at the front part of the panel.



Once things matched up, I clamped the piece and used the same closet dowel I used previously to add a radius bend. This helped me match the profile of the previous tunnel section and bring it back to a point at the rear corner of the panel. Again I bent this by hand, placing one hand on the sheet and one on the back of the closet dowel and working back and forth along the panel in small incremental bends until I got the desired bend angle.



Here is the piece after hand forming. You can see while it is close, the front of the panel does not meet up with the previous panel just yet and the rear of the panel is at the wrong angle to meet the floor.



This is where tipping, flanging, and relief/pie cuts came into play. I started by tipping the rear edge using my offset upper die and polyurethane lower die. The offset die puts pressure on the material to yield it along the line while I and physically pushing upward at the opposite end to bend the flange. Again this takes some iteration.



Not shown, I also added flanges around the perimeter of the piece. I added a pair of Clecos to hold the the piece while I checked fitment. In the photo below, the piece is not fitted correctly just yet. It's sitting low and the flanges are not engaged correctly where the pieces met the tunnel.





Getting this piece to fit to my satisfaction took a bit more love that the previous ones. First I had to pie cut the front corners because I did not have a good method or tools to shrink them. Second, I needed to reposition my flange locations; after fitting it in the car I realized they were off by just enough that I couldn't get the panel to pop into place. So I actually flattened the side flanges back down using a hammer and a backing block, then marked off new flange locations roughtly 1/4" higher on the part and redid the flanges. That bit of rework made all the difference in fit and I was able to install Clecos to hold it in position.





At this point all the metal forming was done and it was beginning to set in that I might not get to play with my bead roller for a while. I took all the Clecos out and brought the pieces out for cleanup.



At about this time, mysterious monoliths started showing up in front of my house.



I primered the panels top and bottom using U-Pol copper weld through primer.



Next I used a Beverly punch to add holes for plug welding. Most areas I attached using plug welds, but some I stitched depending on what made sense for the particular area.







I am really satisfied with the plug welding approach. It was a lot easier for me to pull off than overlap stitch welding or butt welding, although by the time I finished this I felt much more comfortable with tackling those kinds of jobs down the road. To keep things from rusting, I dusted the welds with more copper primer



*I also rattle canned the bottom side of the tunnel with some satin black (still wet in the photo)



With the underside of the tunnel painted, I was able to reinstall the transmission for good.





Now's a good time to show you the shift knob I designed. I sent this design to Twisted Shifterz and they custom engraved it for me. I am kind of curious what percentage of the population would be able to drive my car now that I've done this conversion.



That's all for now. I'll come back and add more thoughts and updates later down the road.

[Graham08]

Nice work on the tunnel! You don't need a ton of expensive tools to do nice sheet metal work in the thinner gauges...as you proved here. I have a couple sets of those handheld shears that do really well when you don't have a shear. Careful marking and a steady hand will get nice, straight cuts. I have had a set of Milwaukee 18 gauge shears forever, and more recently got a set of Kett 14 gauge capacity...they really do cut 14 gauge well. I've found that clamping the material to something solid while you're cutting makes a big difference in how straight the cuts come out.

Are you planning to hit the seams around your tunnel with seam sealer at some point? Plug welding works great, but it can allow moisture to get between the panels and rust down the road.

[TheBandit]

Thank you! Yes I absolutely will be seam sealing, but first I need to strip the floors, repair rust areas, close off holes, and paint. I decided to drive/enjoy it for a bit before I do that finish work.

I blame Jaysin (RIP) for showing me how much can be done by hand with sheetmetal.

[TheBandit]

So many updates to write up and so little time, so here are some short clips instead:

Here is what it looks like to operate the Silver Sport STX short throw shifter on the 6 speed. The short throws with this shifter are amazing. Moving 1st to 2nd I just pull back with slight pressure left. Moving 2nd to 3rd, I can just push forward and it will find it's way naturally over to 3rd. 3rd to 4th again I just pull back. The movements are short and crisp. This is some mild, low RPM shifting - just wanted to capture the shifter movements.


With break in miles behind me, I was finally ready to dump the clutch on those poor tires. Rowing through 1st, 2nd, and (briefly) 3rd while doing a rolling burnout was so much fun! I'm sure it could keep spinning up into 4th gear, but I'd prefer a more open space for those kinds of shenanigans. I plan to practice some clutch kicking & drift as I reach end of life on the current set of tires. I've had a goal for the longest time to execute a forward 360 spin in this car. That will take a lot of practice and open space - there is a very specific sequence of steering and clutch to make it happen and this car has a limited steering angle.


I have more to write up on the trans install. If you follow me on Instagram (@chevyhotrodder), you know I also just finished installing a Ricks Restomod tank with a Gen V Camaro SS fuel module and Vaporworx mechanical regulator. The fuel pump was failing on my modified stock tank and I decided it was time for a more reliable setup. My how the options have changed since I did the swap! I started this thread over ten years ago now and I've had the car driving over 5 years. So much has changed, but the engine continues to make reliable horsepower and I LOVE driving this car.

[TheBandit]

Going on a tangent, I made a little short last week with the Nova about driving at night. I am ratchetting up my videography this year and this was a fun little project to get familiar with on-car camera mounting. Let me know what you think