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  1. #1
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    Default The Next Generation. 3G T.A.

    We are sharing this hoping to expand the idea of what a Pro-Touring car may be. Or, a certain type of PT car. Like, a Super PT. For this, it is time to go outside the box. Way outside. We are pretty far along in the project now, but let me go back and start from the start.



    About two years ago Keith Corrigan and I (Rob MacGregor) started having a discussion about a new car build. Not so much about the car itself, but the concepts, directions, and rules for a new build. We studied the past builds of ours, most currently the HellBoy C10 and his Velocity Camaro. Both are solid competitors and great drivers, and, both have reached there performance limits (without major reconstruction). We talked about the current crop of fast cars, The Leisinger 'vettes, the ridetech 48hr vette, Dusold's Camaro, and such. What we liked, and what we didn't. Some discussions focused on events and their rules. So we have gathered up some rule books. SCCA, SCTA/Bonneville, Silver State, PPIHC, USCA an more. We may not go to any of these, but, a well built car should be capable of attending. If we can fit in here, then others like the Texas Mile, Ohio Mile, Sand Hills, and other Hill Climbs are also a fit. A car capable of the Power Tour, The One Lap, Cars and cones, a cruise to the local BBQ joint. A Supercar with stamina.

    This thread will look different, and I hope to include sources and part numbers along the way. We have also summarized many discussions and topics, these will be posted like pictures, from the saved documents. AT the end, we will disclose the final hour count and total cost to get the car out to it's first event. We both feel strongly that the "Why" you do something is maybe more important that the "How", so, those discussions will be included.

    The car itself, an '85 FireBird. We'll cover the "Why" of that later. How far will we go? FAR. BTW, if you are not a subscriber to "Race Car Engineering" (magazine) or "Hi Performance Academy" (facebook) you want to consider doing so, it will help you keep up.
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  2. #2
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    Rob,

    I know why these 3G F-bodies are not popular, but have considered building one myself for events such as Sandhills and Big Bend, along with standing mile events such as the Big Blue mile. The aerodynamics are excellent. The cars also have a good shape and proportions for high speed driving.

    What they lack in character, they make up for in potential.

    I just never liked the strut suspension in front. The rear is not bad. With a new front stub and some work to the rear, both of which are available in your product offerings, I expect this car could reach a new level of pro-touring performance.

    I am excited to see how this turns out.

  3. #3
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    Thanks Bill. To be Honest, I kind of think of these as the "Disco Camaro". But, I am coming around.

    The choice of 3rd gen Firebird was mostly Keith's. - Hopefully I can get him to chime in on this. But, there are some compelling factors.

    WheelBase 101"
    Width 72.4"
    Weight 2868 lbs (4 cyl - 5 speed - hard top)
    Drag CF. .29

    BTW, these cars still hold the record for the lowest CF drag of any US production car. Not much down force, but pretty slippery. I would hate to know the CF of the HellBoy. :(. And, the underside of these cars is pretty messy, so I think we can smooth it out and help with some down force. At a factory spec wt of 2868, there is a plus. Some classes have no weight specs, others have a set minimum, and some use the "10% less than OE" - That would be 2581 lbs. While we are going to be VERY weight conscious during this build, I don't really want to break the bank with Carbon Everything. I think we can be smart and sparing in this regard. The 101" WB is nice, good for short course stuff. C-5's are 104, and C-6's are 106.5 (or so). Compared to Velocity's 108, It's about 7% shorter. The width is not bad, we are going to try not to make it too 'Fat', tight courses penalize a 'wide stance' car (or truck). So, we went out looking for a 4 cyl hard top bird with a straight body. This is not as easy as you may think. But, we did find one. Just for kicks we weighed it, with a flat tire and some trash in it, 2893 lbs. Then we started gutting it.


    The OG plan was to use C5 running gear, shorten the torque tube to match, and build a tube chassis to put it on. So, we bought a C5 roller and started measuring. Those are expensive notes, and, we now have a lot of spare C5 parts. In the end, this picture tells a lot. One is a factory C5 front lower arm. It's really close to what we wanted. But, the coil-over mount and sway bar mount were not quite where we wanted them, and, with the wheel specs we're looking at, the wheel hit the arm at 27 degrees of steering. Not enough. Also, the aftermarket "kit" parts to put Del-a-Lum or bearings in the lower arm are pricey (corvette guys $$) So, we built some arms. These use the factory C5 lower ball joint, and teflon lined spherical bearings. The fit in the OE adjustable mounts, clear 36 degrees of steering angle, and weigh less than the OE (chromoly)All in all, they cost about the same as buying a bearing kit for a C5. Now we have spare lower arms. It's gonna be like this a lot.
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  4. #4
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    This should be an interesting build. Looking forward to it, Rob.

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    As part of the original plan, we had decided to build a full tube chassis. The main considerations for this are strength, safety, and weight. Most would think this is going "too far" or pushing the cost "too high", but I hold a different opinion.

    If you start with a 30+ year old platform, the basic build plan today is to repair or replace the floors, add subframe connectors, install widened wheel tubbs, modify the trans tunnel, and maybe the foot well, pedal mounts and seat mounts, then the firewall, and add a cage. Maybe even raise the rear hump and modify the trunk floor for fuel tank and axle travel. So, there isn't much of the OE platform left stock, and, all of this was heavy and expensive. So, if you commit from day 1 to go for it, in the long run, this is the most cost effective approach. (we think anyway).

    So, the F-Bird was gutted, all of it. And then carefully placed on a build cart/table. One of our first spec commitments was a 4" minimum scrub line. So, the body was set so that the bottom of the OE rocker was at 4". From this point, our base chassis layout began to take shape. There are really three sections of the design. Front: IFS, engine, cooling, steering concerns, body mounting.... Cabin: Driver safety cage, controls, electronics, seating, driveline tunnel, .... and the Rear: IRS, Fuel, exhaust... But, the three have to fit together, and fit into the body shell. To assist in setting the front rail sections and suspension mounts, we cut aluminum templates (CNC waterjet) to help hold the upper tubes, using the pre set lower tubes as a base. These template plates also helped to locate the Upper and Lower control arms. UCA, LCA. Suspension design was previously worked out using a mix of Solidworks, Autoware and Suspension Analyzer. This allowed us to model the complete chassis and suspension assembly, apply forces, check for high load areas, and hopefully (though no always) eliminate extra work. I say not always because the physical components are not always what you thought they were, like the LCA's that were replaced. But, that's hot rodding, so we just move along. See you in Columbus. Happy Treasonous Colonial Day.
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  6. #6
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    I agree that these are not the most attractive or desirable F-bodies. But as you pointed out, nothing beats the aerodynamic drag of the 3rd gen F-bodies. And they are light. When it is fast enough, nobody will care what it looks like.

    Is that a Winters quick change rear I see in the photo? I've been considering one for my next build - a C3 IMSA clone. But that is time and $$$ into the future right now.

    The simplicity, strength and versatility of the Winters quick change makes it a good choice in my mind.

  7. #7
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    When we started, we tried to lay down some ground rules. It turned out harder than we thought. If you compare this build strategy to the "normal Pro Touring" build, it won't even be close.
    When we attempted to sum up the current build standard, it looked like this:
    ** Start with a car body that you like, or already have. Buy the current 'Hot ticket' Suspension, Brakes and Rear axle. Add in some mini-tubs and subframe connectors, and maybe a cage for safety. Drop in an LS and a 6 speed, and don't forget the Super trick wheels. Now, some guys go farther, and add some Carbon Fiber parts, and Oh yes, the billit aluminum. Next comes paint and body, and some electronics to make it all work. I know there is more than that to it, but 90% of the builds on here could be put into this category. (maybe a different motor/trans).

    So, here's a little history. In the early days of GoodGuys Auto-X, there was no "Truck Class". After some discussion (and two years of pushing) Ed came around and decided this might help get some more guys out there. So he asked me, "If we create a Truck class, will you come and run in it?" Sure I will! So, I built the Silver Bullet F100 and went to the shows. So, for about three years, if I showed up to an event, I won. There were some good competitors after a while, but I was getting faster as well. So, I won. AND, people were complaining. GoodGuys actually published a letter in the Gazette from a guy complaining that he may as well NOT show up because he had no chance of winning the Truck Class. So, the fun was over. At the end of that season, I got the word. New rules. "If you win you're class, you will move into the Pro Class". I was only somewhat surprised, but now it was the "Pro Class" no longer the "Vendor Class". I only had one question for Ed, "So, that means I have to race Kyle Tucker?" "Yes". Well, that changes things. I can win in the Truck Class, but I can't win in this new Pro class. I need a better truck. So, that winter I built the HellBoy. You can't be bringing a knife to a gun fight. And you guys know the rest. Kyle was the top dog, and with the HellBoy, I was able to race with him, and we are still pretty even in the win/loss column. Some may think I should be unhappy with GoodGuys and Ed for the rule change, but NO. Without the rule change, I may have never built the HellBoy, which has spurred on other builds like Jason Brady's Blazer. So it turns out that change is good, and that as Racers, we all want to push forward and go faster.

    Why is that important? Well, if I had built another version of the Bullet, it would not have been to competitive in the pro class. I HAD TO GO FARTHER. And it's that time again. We cannot follow the current standard and expect to be any faster. It's time for new rules.
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  8. #8
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    Looking forward to this; something along the lines of a Ron Schwarz build, but more(if there is such a thing) and streetable, too. I assume you're looking at less than 6 figures, too?
    Ric
    2002 S10 LS x-cab, V6 auto, Flowmaster aftercat, 17x9 TorqThrust II, Bilsteins, LS-1 brakes. Good parts from 2000 ZQ8 swapped over after wreck.

    1966 Malibu, crazy 331, PG, 4.10 9", (drag car)converting to track toy! Collecting parts for a 3 link rear suspension.

  9. #9
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    Quote Originally Posted by rixtrix1 View Post
    Looking forward to this; something along the lines of a Ron Schwarz build, but more(if there is such a thing) and streetable, too. I assume you're looking at less than 6 figures, too?
    Yes, we do have a budget plan, but I am not so bold as to let it our just yet (in case we are way off) We have a base "this is the goal" number, and a 10% over-run factor. I will give out the full build parts list and hour count in the end.

  10. #10
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    I like the approach. I am eager to see how this turns out.

    Reading the rules is important. I ran Sandhills last year and will be back again. Only this year we will be running fast enough to require a roll bar. They specify 1-3/4" 0.95" wall DOM. Then I looked at the rules for Big Bend. They require 1-3/4 0120" wall DOM. I'm glad I didn't build the cage for my Nova yet. I would have to cut it our and rebuild it.

    It does make it difficult when looking at rules across governing bodies. However, they are all within a reasonable band. One can build a car that will work for almost all of these Pro-Touring/Autocross/Open Road/Shootout/Hillclimb events. It just takes a lot of due diligence.

    I'm very exited to see how you break out of the box we have fallen into.

  11. #11
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    Subscribing.

  12. #12
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    Interesting build. Sub'd and looking forward to updates.

  13. #13
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    Thanks guys. OK, one more general discussion before we really get into it.

    Adjustable * Adjust * Adjustability.

    Now, give it some thought. How many of us (you) have cars with adjustable things on them. Carb jets, distributor timing, valve lash (old news) Fuel and spark tables? OK, how about suspension links, caster, camber, toe, spring load, shock valving, spring rate, sway bar rate, roll steer, instant center, roll center...........

    Most well built street/track cars have all of this and more, in one way or another. Now, in reality, when was the last time you were at an event and actually adjusted something other than tire pressure? Be honest. How crazy is that. We have all of this adjustment available, and, we don't use it. I will risk it and say there are only two reasons for this. 1) Not sure what to do. and 2) Don't have the time to do it between rounds. Now I will argue that reason #1 is somewhat a byproduct of #2. Look, if you don't have time to make a change, you don't. And so, you don't experience what that change might have done, and so you don't gain the experience. You have to be willing to try things to learn, but if the time doesn't permit it, the odds are against you. And so, we come to the one factor in adjustability that would make all of the difference, TIME How long does it take to make a change.

    So "Time to Adjust" must also be a design factor. Looking at a GoodGuys, AX-Guys or USCA event, about 1 hour between rounds is the max. But be reasonable. You have to park and get out of the car, you may discuss the change to be made, look at some notes, and you need time to get back in the car, calm down, and get in the line-up. And, SCCA is a faster loop. So, we set out sights on 15 minutes In this short window, we would like to be able to make a change, be sure the car is set up correctly, make notes, and wrap it up. As part of the car build in total, components must be placed and mounted in such a way as to allow this to be done. And to do this, the placement, mount style, hardware, and component choice all come into play.

    Our list of Adjustments includes: Front alignment (caster, camber, toe, roll center), Rear alignment (camber, toe, roll center, roll steer), shock valving, shock rubbers (if used) spring load, spring rate, sway bar rate (front & rear), Gear ratio, brake bias, ..... Just for kicks. We will add all of this into our decision blocks, and that will make for some compromises. But, if you're not really going to adjust it, it doesn't need to be adjustable. Keep that in mind.
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  14. #14
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    ^ So spot on and so crucial!!

    Subscribed...
    Lance
    1985 Monte Carlo SS Street Car

  15. #15
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    Newton's First Law ".....an object in motion will stay in motion, until some other force acts upon it....." In math terms, that's all performance is. To win, you have follow Newton's laws. Put another way, a 3400 lb car going due south at 60mph, WANTS to keep going due south at 60mph. Rolling friction, driveline drag and air drag are the only things acting upon it to slow it down. Now, you want to turn 90 degrees and head due east, you need to work on Newtons laws. Because, the car DOESN'T want to do that. It wants to keep going straight.

    F=ma another smart guy rule. Force = Mass x acceleration. Next I will translate and butcher. (as this is purely for the sake of discussion, I need no correction. I know this to be incorrect, BUT, it is understandable) How about if I said it this way. Energy = weight x speed ( I know, but I did say Butcher) SO, you get it that a car weighing 3400 lbs going 60 mph has a certain amount of energy keeping it heading in that direction lets say 3400 lbs x 60 mph = 204,000 energy units. Lets call these units "Hexo's" But lets also say that 1 Hexo = 1000 energy units, so we could say 204 Hexos. Just one more way to see it, 1 Hexo = 1000 lbs x 1 mph. OK.

    So, why is this important? well, if your 3400 lb car is at 60 mph and you want to stop, you need to exert a total of 204 Hexos of braking force (and have the traction hold). If your car is heading due south at 60mph, and you want to turn it 180 and head due north at 60mph, it will take 408 Hexos (204 to stop it, and 204 to get it back to 60). So, any speed you can conserve during your U-turn will reduce the amount of Hexos (energy) needed to due the job. Now this may be oversimplified and somewhat inaccurate, but the concept of mass and energy is what we're talking about. And, it is this knowledge that helps us to understand the differences in weight location.

    The first sketch is a top view of a given car. The center rectangle is defined by the centers of the contact patches on each tire. CG (center of gravity) is set in the center of the rectangle. Our first goal is to keep as much weight as we can (in total %) inside the rectangle. With the rule being, the closer to center the better. You may note that I marked "Front Swing" and "Rear Swing" as well. This is BAD. Any weight outside the rectangle acts like a pendulum, or the head of a hammer. It's leverage (distance) from the CG gives it more energy, Hexos, and is harder to control. Front Swing weight will want to keep going straight when the tires are turned, creating a push. Rear swing weight will initially follow the turn, but want to keep going, and drag the back of the car with it. Both of these are "Bad Weight" and will require more Hexos to be used to turn the car.

    The second sketch is a side view of the same car platform. 100" WB, 26" dia tire. 4" scrub line. Note that no CG is marked. For most cars, the CG is somewhere close the camshaft height, but proper weight placement can help lower that. The perfect place for weight would be at ground level, directly on the tire's contact patch, but that's not gonna happen. SO, we have to work in the real world. The closer to the center the better, and the lower the better. An understanding of this will create 'arcs' from the contact patches to the CG. Each ring above is progressively worse. Note that at some point, weight high over the CG is seen as equally bad as low mounted Swing Weight, but this is not so. Any weight placement in "Side View" must also go through the "Top View" test. So, Swing weight in zone 5 could be considered twice as bad as the same weight in zone 5 right over the CG.

    The key here is to understand that a pound here is not the same as a pound there. And, the more bad weight you carry, the more Hexos (energy) it takes to turn it. The only tool we have to "Push" the Hexos around is Traction. Bad weight uses more traction to control, and leaves less available to change direction. In this sense, a heavier car with a higher % of "Good Weight" may be a better performer than a light car with a high % of Bad Weight.
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    Last edited by RobNoLimit; 07-17-2018 at 09:21 AM.

  16. #16
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    Now, lets put some of this to work. When you consider weight, the engine/trans is one of the heaviest single components that you will mount in a car. SO, we had this discussion. Move it back, Yep, everybody gets that one. Move it down. Yep, Got that too. But HOW FAR can you go? Well, we can move it back until it's inside the rectangle, that,s not too hard. And, we can move it down until it hits our 4" scrub line (also known as belly pan, or frame rail bottom). With an LS and a steel bellhousing and stick trans, the lip of the bellhousing is about even with the oil pan. If this is the low point at 4", the crank CL will be about 12"
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    Last edited by RobNoLimit; 07-17-2018 at 09:37 AM.

  17. #17
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    So we started thinking, how can we lower this weight. Well, we know we are going to be running a dry sump oil system. And, we have the pan. It's a low profile pan from A&E. That will help with pan clearance. But, the Bell housing is still the barrier. Not too tought o solve. By using a more race style BellHousing/clutch/starter assembly, like a Late Model Dirt car, we can get that out of the way, and then drop the eng/trans down about 1 1/2" - 2". not too bad for off the shelf gear.
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  18. #18
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    But, that's not enough. I mean, we just did the easy stuff. Now the belly of the trans is at the low point, and the trans can't go any lower. The engine could, but not the trans. How about if we divorce them. We could move the trans back a few feet (more rear weight, closer to the center) AND, we could drop the engine another 2". How do you do it? you ask? Welll, we got a big chunk of aluminum and whittled out a bearing plate. It bolts to the bellhousing and carries an input bearing from a super T-10 (in a wet oil cavity) and also has bolt up provisions for a TH-400 tail shaft. All you need then is a custom shaft that fits a 26 spline LS to a TH400 slip yoke. All in all, it wasn't that hard or expensive. But we did go way outside the box.
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  19. #19
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    Well done. I like the thought put into this build. I like the way you question everything.

    Too often we get stuck in tradition and forget to question why some guy in 1953 decided to mate the transmission to a small block Chevy in a certain way. We carry his decisions forward into 2018 and beyond.

  20. #20
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    Hmmm. So maybe a torque tube style setup with a C5/6 style rear mounted trans/diff assembly. Lower CG, redistributed weight. Me likey

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