'70 Nova LSX swap LY6/TH400

[TheBandit]

After over 2 years with the Procar seats, I finally came to the realization that they just plain sat too high for my liking. It wasn't so much an issue of headroom (although it was tight with a helmet on), but rather I just felt like I rode too high in the car, looking out of the top of the windshield. I still really like the seats, so I decided to do something about it.,

The Procar seats mount on a pair of sliders which in turn mount to a vehicle-specific mounting frame. The frame is made from 1-1/4" wide, 3/16" flat bar and a pair of 9/16" rods. The flat bar is used for crossbracing and four mounting tabs, which attach to the floor and ensure the seat is positioned and leveled appropriately. The seat sliders bolt into the neds of the 9/16" rod. Here's what the frame looks like in the car:



I decided the easiest approach to lowering the seats would be to modify the four mounting tabs on the frame. I found the most I could lower the seat would be 7/8"in, because it would put the shortest mounting tab completely against the floor. So I picked up 7/8" thick stack of washers and began making my own mounting tabs one by one to replace the old ones. My method was to bolt a new tab on with spacer washers, weld the new tab on, then cut off the old one. I made the new tabs from 3/16 flat bar with my portaband and drill press. The bolt located the hole for the new tab and the spacer washers ensured an even drop at all four mounting points. After I welded the accessible side of each new tab, I cut off the old tab, then welded the backside and ground it flat. I'll let the photos do the talking...





























Here is the modified frame back in the car.



In order to take advantage of the newly-lowered mounting frame, I also had to remove the lower mounting tab positions on the seat sliders (which would have brought the seat back up)





Here is the "before" headroom for the unmodified passenger side


Here is the "after" headroom for the modified driver's side.



I'll be damn if that wasn't one of the best mods I've done in the last 2 years. It was like letting my belt out after a Thanksgiving meal - the car just fits me comfortably. I didn't fully appreciate just how uncomfortable I was. The weirdest realization was when I stopped at a traffic light and I could actually see it above me without tilting my head slightly forward to peer up. It's even easier to get into the car due to the added head space at the top of the door opening. Just goes to show the little things really count.

[mikes82GT]

Now it's down to the nit picking fine things...it never ends....sheesh.

[Graham08]

Nice work! I like how you used the stack of washers to effectively make the existing seat frame into a jig for the new tabs.

[TheBandit]

Thank you Graham. I was thinking about making a full fledged jig so I could reproduce the frame from scratch, but this approach saved a lot of time and materials. I know this is child's play compared to the fabrication work you do.

[TheBandit]

I'm gearing up for my next autocross in April and I've made a punch list of items to address. Since the last autocross all I've really changed on the car are the front brakes (now C6 Corvette variety) and the driver seating position. I have a couple of priorities to address before my next run through the cones. First I need to fix the tire clearance issues I have up front; the tires are still rubbing at the back of the fenders. It seems like it got worse when I swapped the brakes, even though I was expecting it to get better. The new brake setup should have reduced the track width by 0.240in per side and I can't figure out how that would lead to the tire shifting more rearward in the fender. Yet somehow it seems to have done exactly that because I'm getting rub in normal driving scenarios that I didn't get before. I did check to make sure the subframe hasn't shifted and it's still in good alignment. I can't think of what else would have changed.

Before I start modifying my inner fender to gain tire clearance, I want to start by seeing how the alignment impacts clearance. Based on my research and looking closely at photos from my last autocross, I think the car could benefit from more camber. At the same time I'm wondering if taking out some caster would improve the tire clearance. So I broke out my old angle cube angle finder and bought myself some toe plates and decided to try a DIY alignment at home.

For my car, I can easily check camber by placing my angle cube on the end of the hub. Caster can also be measured this way, but requires a bit more work to sweep the tires through a suitable steering angle. After doing the research, I came up with a method and explain it in the following YouTube video. I'd love to get feedback on whether this method is correct and if there's anything I might need to do differently.



I decided the easiest way to check toe was to get a set of toe plates. I bought some Longacre Racing ones and they seem to work very well. I may also string the car later so I can check toe side-to-side.

As of now the alignment is as follows:
Camber: ~1.1deg both sides
Caster: ~6deg/6.5deg driver/passenger
Toe: 0in

I'm wondering what effect there may be on the rear tire clearance if I reduce the caster a bit. The way caster is adjusted on my car is by shimming the upper control arm to move the spindle upper ball joint forward or backwards. If I move the upper balljoint forward, that should result in a small forward shift of the tire as well as a caster reduction. Reducing the caster is not desirable but if I can gain a little tire clearance this way it might be worth making a quick change. I'm thinking about going down a degree to see what happens. I also want to see what increasing negative camber will do, both for the performance aspects as well as tire clearance. Now that I have the tools, I just need time to play in the garage and try it out.

[TheBandit]

Last night I played around with the alignment to see if I could increase clearance at the back of the tire. I took 1deg of caster out by adding 1/8" shim to the front mounting location of the control arms. I found it did almost nothing for clearance at the back of the tire - probably less than 1/16in. So I returned the caster to where it was previously.

While I was goofing around, I did a closer inspection of the rub area at the back of the wheelwell and the witness on the tire sidewall. I realized there was no way the rub at the back could be causing the damage pattern on the tire. The area that seems to be getting shaved on the tire extends down the sidewall a bit, eating into the raised lettering/sizing marks. The back of the fender could only really contact the corner of the tire. So I took a closer look under the car and found a small patch of paint rubbed off just inside the top lip of the fender, near the button head bolt I had installed to help with clearance. I swear I had looked here before and didn't see rub, but maybe things have shifted or I just failed to pick up on it. The tire has probably just been rubbing on the button head fastener. So for now to gain clearance I added another degree of camber in by adding 3/16" shim at both locations on my upper control arm. That put me at:

Camber: ~2deg both sides
Caster: need to recheck
Toe: 5/16in toe out

This made a dramatic improvement to tire clearance at the top of the inner fender. It went from roughly line-on with the inside lip to roughly 3/8" clearance. I'm guessing even half a degree would have been helpful and I could probably remove the upper bolt on the inner fender to improve the situation further. I wanted to try more camber at my next autocross anyway, so I may give this setting a try.

Also as you can see the toe changed from 0 to a whopping 5/16in toe out. I will need to readjust that, but since I'm just experimenting at the moment I'm not too concerned. I also need to recheck caster to see if my even front/rear shimming had any effect there; hopefully not.

I'm really enjoying this little experiment. Alignment is something I've always wanted to play with and I'm sure the learning will pay off.

[TheBandit]

Here is a video I took explaining the use of the toe plates for anyone interested. These are a great tool!



Before I readjust the toe, I need to swap out the tie rod adjusters. Always something fun to do!

[CarterKraft]

Originally Posted by Graham08

Nice work! I like how you used the stack of washers to effectively make the existing seat frame into a jig for the new tabs.

No kidding, I would have made a huge jig taken half the day just to do the same thing you did. Genius!

[TheBandit]

Originally Posted by CarterKraft

No kidding, I would have made a huge jig taken half the day just to do the same thing you did. Genius!

I almost went down that path! I'm glad this idea came into my head instead; it sure made quick work out of it. I wonder how many years will go by before I do the passenger side to match?

[TheBandit]

The process of taking and uploading photos takes quite a while so, I've been trying to do little mini videos instead to see if they save me some time.

One of the upgrades I plan for my car "eventually" is to replace the steering box with one that has a heavier feel and faster ratio. I'm doing a lot of hand-over-hand steering in the sharp corners of autocross and there is almost no tire feedback whatsover when I'm turning. The feedback is driven by a servovalve inside the box that uses a torsion bar to regulate assist. Unfortunately that torsion bar is buried in a component that can't be disassembled without special tooling, so I have no idea what I currently have. But I can measure the box ratio, so here's what I came up with:



What I did there was attach a protractor to the output of the steering box and a pointer to the frame. I marked my steering wheel and made two revolutions (720deg) while measuring the angle output at the box. I got 52deg of output, so my box ratio is likely around 720/52=13.8:1. This may be an average if the box is variable; I did not take intermediate measurements to evaluate if the ratio was varying. I did a lock-to-lock measurement also and I got 2-3/4 turns. I also measured the tire steering angle using 180deg steering wheel input (the most I can do comfortably without switching my hands over) and I got 10deg of tire movement. That translates to an 18:1 overall steering ratio between the steering wheel and the tires. That ratio should be a function of the box ratio and the arm ratios between the pitman and the steering arms. Now that I know what I have, I can make a more informed decision when it comes time to select a box and box ratio.

Next, since I'm doing a little more DIY alignment now, I decided to swap the OEM adjuster sleeves for some hex adjusters to make toe adjustment easier. Here's an install video:



There are several sleeve options out there for 67-69 Camaro / 68-74 Nova. I went with the QA1 pieces, because they were steel and have a good hex length to hold onto. This is an area where I feel more comfortable with steel over aluminum, both for strength-in-use as well as resistance to rounding out with wrenches. Hopefully these will make toe adjustments easy.

[TheBandit]

Yesterday I got back to the garage, bounced the suspension a bit to settle things, and proceeded to adjust the toe. The hex sleeve tierod adjusters were really easy to adjust and I'm feeling great about investing in the toe plates. I was able to adjust from about 5/16 toe out to 1/16 toe in just a few minutes. I will check again after I have a chance to drive the car and resettle the suspension.

Since it was easy enough to do, I decided to get a point of comparison for what I'd seen on my Nova. Specifically:

Originally Posted by TheBandit

I did a lock-to-lock measurement also and I got 2-3/4 turns. I also measured the tire steering angle using 180deg steering wheel input (the most I can do comfortably without switching my hands over) and I got 10deg of tire movement. That translates to an 18:1 overall steering ratio between the steering wheel and the tires.

I decided to try a similar experiment with my daily driver: a 2016 Subaru Outback. I measured the same attributes and got almost the same results. The Outback had just under 3 turns lock to lock and gave me about the same 10deg of tire movement for 180deg steering input.

With ratio I think it's all about making sure the steering isn't too sensitive / twitchy on the road for normal street driving while reducing all the crazy hand shuffling I do in autocross. I'm going to see if I can find other data on overall steering ratios and get a sense of what I might want on my car. Hopefully I can actually drive a car or two with known overall ratios so I can get a sense of what lane changes and panic maneuvers might be like. My potential choices of ratio include 12.7:1, 10:1, 9:1, and 8:1 depending on whether I go with an 800 series box/rebuild with Lee Power Steering or a 600 series box from Turn One.

Speaking of panic maneuvers, last week I was passing some slower traffic on a four lane surface street headed home. Someone apparently couldn't see around the slower traffic to know I was coming and they pulled out in front of my car. Not only that but they stopped in my lane while looking for additional cross traffic. I was doing roughly 40mph and I'd guess I had around 2 car lengths to react. I was boxed in by cars on the right and the median on the left, so my only choice was to lay on the brakes and pray. All the practice I had adjusting my proportioning valve helped, because I was very aware of and pretty near my threshold braking. The tires complained a little, everything inside the car flew forward, I hit the seatbelt lock, and in a split second I managed to stop the car just shy of hitting the other car. I have no doubt I would have t-boned that car and potentially crushed another person if I hadn't gotten my brakes up to snuff with this last round of brake changes. I'm also doubtful I could have stopped on the old tires I used to run when I had 15" wheels. Thankfully my car is unscathed, the other driver did not get t-boned, and I was able to just drive on home afterwards. This is the value of making an old car stop and being attentive while driving.

[TheBandit]

In April I finally got serious about swapping the steering box. I found a great deal on a new-in-box Sweet Manufacturing "Sportsman" 700 series 12.7:1 box with a 0.235in t-bar. For reference, many of the major "pro touring" aftermarket companies offer 12.7:1 boxes with 0.210in t-bars for this application, so a 0.235 is considered "heavy". I decided to give it a try anyway.



The first step for getting the old box out was to pull the hoses and disconnect the rag joint from the column. I used a large syringe to pull as much powersteering fluid out from the reservoir as I could before pulling the hoses, which helped minimize fluid mess.



Next off with the pitman arm using a puller. Then the 3 bolts holding the box to the frame were removed and the whole box dropped down & out.





I found the rag joint was torn in a couple places and definitely ready to go in the trash.



After putting a new rag joint onto the new box, it was lifted into place and bolted to the frame.



An important step at this point was to loosen the steering column at the firewall and under the dash so the steering column could be aligned to the steering box. Then the rag joint was attached to the steering column and finally the steering column was tightened back down.

After that the lines were reconnected, fluid added, and the system was "burped".



Finally... driving!



Wow what a difference! This completely transformed the driving experience. The feel of the heavy t-bar is just incredible - I feel so much more connected to the car. Every corners feels like a fun corner now, even just tooling around town. This "heavy" 235 tbar steering box has been one of my favorite ever upgrades to the Nova. My first impressions were filled with anxiety thinking this might be too heavy for street driving (parking, driveways etc), but now that I'm used to it I am in love with the go kart feeling. I love having a sense of what the tires are doing and I can't wait to get to a track or autocross.

Since I am trying the quick vlog thing, here are some videos I made related to the swap and driving impressions:

Pt 1: Pre-Upgrade Driving Impressions


Pt 2: Removing the Old Stereing Box


Pt 3: Post-Upgrade First Driving Impressions

[alwaysFlOoReD]

That was interesting. Thanks for the comparison vids.

[TheBandit]

Thanks. I'm really glad I took the pre and post videos driving the same loop. These long-form videos are a bit slow. I'm thinking in the future I'll try to edit things down to under a few minutes and try pepping up the conversation a bit so I don't put people to sleep.

[TheBandit]

I have been enjoying my car entirely too much lately, so I decided it was time to convert my driver back into a project car. Jack stand queen felt a little too fancy for me, so the first order of business is getting it up in the air on something stable. I decided to build a set of wooden wheel cribs from 2x4s.

DIY Wood Wheel Cribs

Wood wheel cribs have become popular among the pro touring build crowd because they are relatively inexpensive and provide a stable means of getting the car off the ground. To start the project I bought a stack of*
2x4 and a large box of #10 2-1/2" screws. To be exact, this project requires 11 8ft 2x4s (only 10 are pictured because I had another on hand at home already) and 224 screws. All this is to make wheel cribs that are 14" x 16" and 8 layers tall.



I setup a crude stop to get consistent length out of my miter saw. This made the cutting very fast - I think I had all the cuts done in under 20minutes. I cut a 3 pieces of each length from each 2x4, then reset my saw stop and did the remaining pieces of the other length from the remainder of the boards. This left me with a very small waste from each 2x4.





Next I predrilled and screwed each 2x4 down to the previous in an alternating screw pattern. This took FOREVER. A wise person would use a framing nail gun instead - unfortunately I don't have one!







Finally I got the car up in the air. So much room for activities!



Since I live in Southern California where earthquakes do occasionally happen, I decided to strap the stands to the tires so they will stay with the car if things move around.




Now that the car's up in the air, I will start tearing things apart in prep for the (drum roll please) Detroit Speed weld-in subframe connectors and (much bigger better drum roll please) Magnum-F 6-speed manual transmission.

[Graham08]

Originally Posted by TheBandit

Your woodworking shop bears a close resemblance to mine!

I'm interested to see how this goes. The subframe connectors should make a noticeable improvement in the handling for your autocross activities.

[entropy]

Nicely done!



E

[TheBandit]

Thanks both. I like the idea of building things with wood, but in practice I don't do it often, hence the temporary driveway setup. I've had the car on the cribs for a few weeks now and they are holding rock steady. I wish the car was a little higher so I might make some inserts to raise it more. There's enough space to roll under on a creeper, but I'm not sure if the transmission with scissor jack will fit.

[TheBandit]

Okay I'm trying something new by making a video. I think I may be better at photos and typing in a forum, but heck I tried. Check it out and please let me know what you think.



I'm thinking the floorpan is in worse shape than I realized and my fit-up kinda sucks. Feeling a little discouraged but I'll figure it out.

[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.