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43 Posts
Discussion Starter · #1 ·
I have a 1973 Opel GT that was raced in the mid-Atlantic area in the 90s. It was pulled out of storage some 20 years later and given to me. In 2016 I updated the cage a bit. Cleaned the fuel cell out, removed the lights, and added some small LEDs for night racing, plus to save the light pods from damage, and towed it down for a 10-hour endurance race at Sebring International. Did ok, though the carb gaskets were dry rotted and the car would only rev to 4k. We were the slowest car out there by far but finished mid-field. 80mph top speed, and a 78mph race average. Only used the brakes at the hairpin. It was fun, but scary being passed by 150mph cars.
Then made a few small changes by added rearview cameras, and fixing the carb. Next race at VIR South in 2017. Had some ignition issues, caught fire, fixed, got back out, and finished upper mid-field.

Got a job working full time with the sanctioning body and basically parked all my own race cars.

So... kinda want to take the Opel out again. I have some time this winter to get all the issues sorted, do a track day or two once the weather improves, and then take it to a ChampCar race. Maybe Sebring or Carolina Motorsports Park. So the first part of the prep is to see what we have. I never weighed the car because I really did not care. So today I did it.

She is a fat little thing.

Full ITA prep.
full cage 1.5"x.120 wall
Kirky aluminum road race seat (My kevlar Cobra Sebring full containment seat stuck out the window, I was sad)
Fiberglass dash, but with all the heater stuff in per IT rules of the 90s.
15-gallon fuel cell 1/2 full
Tube rear bumper to protect the cell. Overkill, but we got hit at Sebring and only got scratched paint while the car that hit me suffered massive front-end damage. It was a team car. The first rule of racing. Don't hit your team car. I was sad again for awhile. So glad I added the extra weight to the rear.
Right now it has Honda Civic aluminum 14x6 wheels with 185-60-14s. Was surprised by how comfy they were at Sebring. did well in the rain as they are all-season. It's what any self-respecting race car builder would use.
OK. so today I weighed the car.
LF 532 RF 491
LR 442 LR 460
Total 1925 Pounds


I want to get it lighter. But as has been shown, I think I would destroy the car, which I don't want to do as it is rust-free, and has raced at Sebring.
I think I will cut the cage out and rebend a new cage using today's cage standards and use 1.5x.095 wall.
Thought I would update this post with real numbers as it shows up on the top of Opel GT weight Google search.



· Ron in FL
3,633 Posts
Great story, Bill.
The little Opel definitely deserves to see the track again. I hope you are able to make it happen.
Others here may have some suggestions on how to make the car lighter. I think the curb weight of a stock 73 GT was a little over 2000 lbs.

· Registered
875 Posts
Thank you so much for posting. What a great fun project. I am jealous. I have never had a car on the track. Spent time wrenching on a drag car between races a few times; changing out valve springs, removing trans to reface the clutch disc, checking plugs, etc. Lots of fun. Guessing at my age, I won't likely ever get to get behind the wheel at a track, even though Hallett is just a little over an hour away from me.
Glad you rescued it.
How many feet of tubing in your cage? You will save about 1/3 pound per foot. Actually, .343 pound per foot. That's a lot of work.
Good luck and keep us posted.

· Registered
675 Posts
A set of Longacres scales goes a long ways. I would encourage every performance minded enthusiast to weigh all four corners. Unless you have access to a pull down rack or the plate that was used for fabrication, you can do no better. You will benefit from your suspension setup efforts. Good to see that you are having "fun" with it. Keep up the good work.

· Registered
34 Posts
Cool post. I actually don't know how to get weight out without hacking the poor thing up. We pulled about 80 lbs out of our race car by replacing the windows with plexi, gutting the doors, and pulling the headlight buckets out. but it sounds like you already did all that.

If the cage was designed for it, a lot of the unibody (particularly the trans tunnel) would become structurally redundant to the cage, and could be hacked out. The floor and trans tunnel are really heavy, covered in rustproofing, could be replaced with something lighter. If you drop the engine and trans a little by putting in some solid mounts, you can also open up a lot of room inside the cabin by re-making the trans tunnel too.
But if you don't want to hack it up, I'm at a loss.

The spec E30 wheels from 949 racing are hella light. But probably not a whole lot lighter than your civic wheels.

I'm guessing you already have a header.

I have often thought about grinding the rear axle housing thinner in non-essential places, or even cutting large sections of it out and welding in thinner metal to keep the oil in — either that or leaving it hacked up and putting in oil seals to keep the gear oil in the pumpkin (all of that is a ton of work for a few pounds, but it's unsprung weight).

Switching to discs on the rear brakes might save a little weight, but probably only ounces.

We are running an aftermarket civic aluminum radiator. The radiator is a touch lighter, but the capacity is greater, so it results in a net gain once you fill it.

The nose is surprisingly heavy (I cut the front one off at the middle of the front fenders once). I bet you could take 40 lbs off the car by hollowing everything out everything forward of the front suspension, including the insides of the headlight buckets. But once again, you don't want to hack the car up.

I guess you could have a custom, carbon-fiber Opel engine made up and paint it to look like the stock block...

Sorry, I can't think of anything very helpful.

· Registered
43 Posts
Discussion Starter · #6 · (Edited)
Thanks for the replies guys!

I have the 1995 issued SCCA logbook #42-1298
Weight was 2000 in as raced condition without a driver.
It was classed in ITB
cage is listed as a 1.5" x 0.095. The bars I have cut out and replaced verify this.

It's pretty awesome. I have the complete history of the original build. All receipts and notes of Larry Davis and the three owners since. I have built a book with the history included that goes with the car.

Handwriting Rectangle Font Writing Paper

Handwriting Rectangle Font Writing Parallel

Handwriting Font Line Material property Document

Font Book Parallel Music Pattern

So this is a 1973 GT with a balanced and blueprinted 1969 1.9. Some tweaks were done to the pistons and it is a high compression engine.
After sitting for mostly 20+ years, the car runs awesome with zero smoke or oil burning.
It currently uses a 38DGAS carb and a very old 4-2-1 header.

The car is on jack stands awaiting some sway bar bushings and other hardware from OGTS. The fuel system has been removed as the ATL fuel cell expired some couple of decades ago. The fuel hoses were not in great shape. A new SFI rated 16-gallon Jaz fuel cell is ordered and on the way. Hose, fuel filter, and a new Carter pump are awaiting the tank install. Old ATL box in the image.
Plant Rectangle Wood Grass Gas

The car had a fire in the carb at the last race. Fire marshalls dumped 5 extinguishers under the hood. It caught fire during a red flag for another car fire. My driver was sitting in front of the start-finish line and the car would not restart. I was standing about 30 yards from the car doing a live broadcast when I heard the whoosh of the fire starting. The driver pulled the pin on the Safecraft fire system. It's impossible to extinguish a fire inside the carb when your fire system is pointed at the block. lol. We got towed back to the paddock, and after 20 minutes of fixing, and replacing charred hoses, and replaced the now empty fire bottle with a backup, we were out racing. Pretty tough car.

A new Lifeline Fire Zero 360 Novec 1230 will be ordered in a few weeks.

I installed new rear lights. I shoved a set of LED strips on for the Sebring race. It looked ugly. But now new LEDs look much better. I am not 100% happy with the install. So I ordered some newer LED lamps and some fancy mounting brackets that I will mesh into the back of the car. Still keeping the round look.
Some new rain lights will be coming out soon that have the latest FIA ratings. So that will mount where the plate used to be.
Car Vehicle Hood Automotive lighting Light

I will update this thread as the rebuild to 2021 specs happens.

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43 Posts
Discussion Starter · #7 ·
The first of the cage changes was to remove the dash bar. It was way to low. I am 5'11" and 240 pounds. So round'ish. It is not easy for the more "mature" folk to get out of the car with that low dash bar. My 21-year-old son is also 6'5". So, he needed more ankle room.
Motor vehicle Hood Automotive tire Vehicle Automotive design

I moved the bar up above the steering column.
That was easy. Hugely betterer!
Hood Automotive tire Motor vehicle Vehicle Bumper

Also found that the dash bar was not fully welded. Even professionally installed gages fail our tech more often than not. It's pretty wild. I am the marketing director for the TireRack.com ChampCar Endurance Series. I work with tech inspectors on race weekends.

Automotive tire Fluid Wood Water Gas

Next was the harder job of moving the upper front window bar away from my head. It was scary close. I crashed my Toyota MR2 race car at VIR at over 90mph and hit my helmet on the roll cage. I suffered a brain bleed and concussion. That made me rethink seats and driver placement.

Tire Automotive tire Bicycle tire Wheel Tread

So cut that bar out, cut a new section of 1.5"x.095, and bent it to conform with the window curve.
I'll install an Earnhardt bar once I get the polycarbonate front windscreen made.

Land vehicle Tire Bicycle tire Vehicle Window

Temp window installed to test chearances. The other window was cracked at Sebring. When I pulled it out, it cracked way more.

Automotive parking light Car Motor vehicle Hood Automotive lighting

· Registered
43 Posts
Discussion Starter · #9 ·
I work for an auto racing santioning body, and I will be away for the next three weeks putting on endurance races. VIR 12-hour this weekend. Next week Harris Hill, San Marcos, TX. Then NCM Motorsports Park in Kentucky a week after that. Then I have a weekend off to work before I hear to Daytona for a 14-hour. Fun times.
This is my post retirement job. It was supposed to be just a fun job. I work harder now than I ever have!

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43 Posts
Discussion Starter · #10 ·
Oh. And I have a lot of stuff/parts in the mail.
I have a buddy that builds racing headers and we will be building a 4 to 1 to replace the long tube 4-2-1. 3" side exit exhaust using a side exit spintech muffler.

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43 Posts
Discussion Starter · #12 ·
The cars are broken up into classes for by engine size. The GT is in the A-class for small-bore engines.
Within ChampCar’s endurance racing program there are five (5) classes of racing:
• CLASS A –All cars with engine displacement
of 1.91 liters and under
• CLASS B –All cars with engine displacement
between 1.92 liters and 2.4 liters
• CLASS C –All cars with engine displacement
between 2.41 liters and 3.91 liters
• CLASS D –All cars with engine displacement
of 3.92 liters and higher
• CLASS EC – All exception class cars (cars that don't meet our rules, but at the discretion of the race director can run in this class.)

Most of the time D-Class does not finish in the top 10. Class C is the best compromise between power and fuel usage. Though class A and class B do win their fair share of events.

2-hour maximum stints.
5-minute minimum fuel stops. Once the gas cap comes off the stop is times at 5-minutes. No gas cap off, swap out your driver at 2-hours and get out of the pit.
The GT can go almost two stints on fuel. This how we are the slowest car in the world of ChampCar racing but finish mid-pack.

The goal is to go to Sebring in December for the New Years' Eve Double-7-Hour Enduro Weekend with the Opel GT. 2 races.
I want a top 10 finish on that track in each race. The suspension is the raciest that OpelGTsource sells, and it is still like a nice easy chair on that track as compared to my Toyota MR2. And the GT is so easy to drive, not wanting to kill you every lap.

· Super Moderator
15,223 Posts
Oh. And I have a lot of stuff/parts in the mail.
I have a buddy that builds racing headers and we will be building a 4 to 1 to replace the long tube 4-2-1. 3" side exit exhaust using a side exit spintech muffler.
What’s your engine specs? It’s really easy to go too big on a 1.9 engine which does nothing for power and really hurts reliability.

These engines already run very high EGT’s, so unless you get the intake runners, intake manifold, and carburetor to really flow well, I suggest erring on the small side for your exhaust. Otherwise cracked valve seats, burnt exhaust valves, high coolant temps and high fuel consumption can be expected.

For a warmed-over 1.9 with flat top pistons, I’d stick with no more than 1.5” primary tubes and either 2” or 2.25” (max) main exhaust diameter.

Here is an ITB-spec Opel GT header and exhaust I built as an example. I went with 1.5” primary tubes, 34” long, into a 2” merge collector, and out to a 2.25” exhaust.

Worth noting is the fact that this system I built is for the fastest ITB Opel in the US, and one of the fastest ITB cars period.


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· Moderator
1973 Opel GT
3,924 Posts
I want a top 10 finish on that track in each race. The suspension is the raciest that OpelGTsource sells, and it is still like a nice easy chair on that track as compared to my Toyota MR2. And the GT is so easy to drive, not wanting to kill you every lap.
You really should look into fabricating your own Watts link or multi-link rear end suspension. RB has done one I believe. I have a diff cover from Europe that has 3 threaded holes to create my own Watts link. Kyler is doing a Watts link on his autocross GT. You might also want to buy a diff from Quaife, they also make a complete set of gears for the 4 speed and that might be worth it. The stock 4 speed isn't exactly a robust transmission. I think I've heard it's hit or miss on it failing in race cars. Manta Rallier and RB can chime in a lot more on that than I can.

I had a good laugh about the MR2 wanting to kill you every lap. Glad to know the gen 3 oil pan that was on my parts shelf will serve time on a race car. You might want to talk to Bob (opelgt722002) about the roller rocker setup he has that he is considering selling. It's the unobtanium Rally Bob design. I have the Harland Sharp roller rockers, which are a tad different in design. I think the HS rockers are better suited to street use in a GT that wants to keep the stock look and the RB design rockers are probably better suited at high RPMs in a race car. That isn't from personal experience trying out the two, just my observations about the design differences. The RB design has a stud girdle and possibly lighter weight rocker bodies. The HS rockers use a connected trunnion design to provide stability and looks like they would weigh more. The RB rockers require a spacer for the valve cover btw, if you get them.

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43 Posts
Discussion Starter · #15 ·
The car is a 190s full ITA build. The rear suspension is all being jointed.
That's all I know.

I have never had the cam cover off. Will soon to inspect and see what we have.

That header is sweet.
If you are still making items like that, can you Message me a price for one of those.
I will take your notes about pipe size. 2.5 it is. That's what is on it now.

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43 Posts
Discussion Starter · #18 ·
Took a few hours to play today.

Cold air intake. Why? Because I have tools and I think it looks cool. Lol.

Installed the new to me NASCAR rear view mirror using Chinese made mounts. I can actually see out the back now.

There is so much bondo on this car. I hate it. Maybe I should just get the widebody flares. Crash damage from the 2018 VIR 12-hour.

Toyota MR2 mirrors. They are large and the drivers can see better. Slow car around 145 mph cars can be a bit scary.


Still awaiting a lot of parts from the man in brown.

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43 Posts
Discussion Starter · #19 ·
Been off putting on races. Next week I am at Daytona. Fun times. You can watch us at www.champcar.live. I am the pit reporter this weekend.

Weighed the car at 1925 pounds. That's the way I raced it the past two races.

Cut some cage bars out. Redid a couple. Cut sheet metal out not needed to go fast.
Zero fuel. No wheels and tires. LoPo battery. Now at 1565. I think I can get it down into the upper 1400s. I think the roof will come off and replaced with a thin fiberglass copy. Still debating.

Got the fuel cell. 16 gallon. Got steel to make a cage for the cell. I also need to rebuild the floor where the bar from the diff mounts to. It bends a bit too much under stress since the previous owner cut the floor to mount the cell. Still awaiting some required venting parts and fittings. Plus the fuel fill hose.


Removed the stock oil pan and cleaned out the trans. Then installed the new oil pan/trans cooler.


My diff was welded by the builder of the car. Sometime before I got the car it broke. It always had a little play. I did not know it was broke as I have never had a welded diff.


I broke out my big welder and welded this bad boy up properly. It works perfect now.


· Registered
43 Posts
Discussion Starter · #20 ·
Been busy with work. But I'll sneak away every now and then to do some work on the car.
Worked on the cage a bit. Plus mounted the fuel cell in the passenger seat area.
Also mounted the rear wing today.


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