GT40 vs the Competition

When ERA built my first GT40 had 15" wheels that limits the size of the brakes. The brakes were not power assisted and the engine was down in power (330ci). I ran at Road America and the Mustangs were faster and could go deep in the turns.

My second ERA the engine was a 409 with 17" wheel with bigger power assisted brakes. Race rubber etc. The car was a total different car and could run with modern cars at Poconos racetrack.

Great info. So modern brakes are a must.
 
There is just something special about a the 1960s performance cars like a GT40, Cobra, Daytona Coupe or even Corvette Grand Sport vs today's performance cars. I'd take a GT40 vs a new Ford GT any day but that's mine vintage preference. It's funny to watch people flock around a 1960s GT40 replica over a 2005/2006 Ford GT. Just something special!
 
I've had a CAV GT40 and, more recently, a Z06 C8. The CAV had a 347 with Holley, 15 inch wheels, stock brakes. Pretty modest in all respects.

While I loved the CAV, it came nowhere close to the performance of a modern sports car. The modern 911 turbo - much, much faster, better brakes, better handling. The CAV could not keep up with a F360 on the track. The CAV would be a very distant sight in the rear view of the Z06.

You really can't compare a 50 year old car/design to a modern performance vehicle. It's not even close. Just my $.02 with my own first hand experience.
 

Howard Jones

Supporter
I have run my SLC a lot with GT3 Porsches. All in all my best estimate is a 450hp SLC on R7 Hoosiers can run very similar lap times IF the drivers are comparable in skill. The one big difference is I have a G50 5-speed GRRX with a Quiafe TBD in it and I have to row through the gearbox myself. Coming off a slow corner onto the longest straight I am in 3rd and by the time I have gotten to 5th the Porsche has shifted 4 times with his PDK and pulled me by 2-4 car lengths. A GT3 Porsche has about the same power and really isn't much heavier if at all. It's the ability to make instant shifts.

At the end of the back straight we are right at 145-150. I can brake with him and maybe even get my couple of car lengths back, but it is clear I need to do 2 perfect downshifts back down to 3rd, get the breaking right, and turn the car in at the right spot. Coming off that corner we will be equal more or less because we will stay in third for two more corners, But the next time we need to make 2 or 3 upshifts the same thing happens. I will inevitably make a slow shift going up or down and if I do I can't get that time back. In 8 laps he's gone.

I intend to fix this with another 125 HP. We'll see how that goes.

But it will always come down to the driver in near-pear cars.

So will a GT40 kit car go as fast as a GT3, Yes. How?

1. 400 inch small block @ 500-550HP
2. 18-10F and 18-12 rear wheels running dot slicks
3. Correctly designed suspension geometry suited for the tires
4. 14 inch rotors in front and 12 in rear with appropriate calipers. All vented correctly. I don't think you need antilock brakes. BUT you will need to two-foot the car in the braking zone..................WELL.
5. Keep the car down to 2500 pounds or as close as possible. Leave ALL the bling off! Figure 10 gal fuel tank. You will use about 6-7 gals every 30-35 mins.
6. You will need to spend a lot of money on a modern racecar transaxle that can be shifted electronically and match downshift revs automatically with the engine management computer.
7. The car will need to run an efficient splitter and dive planes on the front and a large spoiler on the rear. Flat bottom the car as much as possible while running the car in a front-down attitude rake. I don't think you will need a wing. The total downforce on the front of the car can be balanced with a spoiler at the rear.

How much? If you don't pay anyone to do anything for you so the labor costs are near zero, you will have about $50K in the basic kit, $65K in the power train, $30K in the engine, and another $30K in the rest. About 175 grand if you run it in jelcoat and install one race seat.

Maybe you should budget for another 10 or 15K for................the other stuff. We all know how that goes. You will still be a lot under a Porsche.

I just did a build-your-own 2023 GT3 RS on the Porsche website. Comes out to $280K USD
 
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Neil

Supporter
I have run my SLC a lot with GT3 Porsches. All in all my best estimate is a 450hp SLC on R7 Hoosiers can run very similar lap times IF the drivers are comparable in skill. The one big difference is I have a G50 5-speed GRRX with a Quiafe TBD in it and I have to row through the gearbox myself. Coming off a slow corner onto the longest straight I am in 3rd and by the time I have gotten to 5th the Porsche has shifted 4 times with his PDK and pulled me by 2-4 car lengths. A GT3 Porsche has about the same power and really isn't much heavier if at all. It's the ability to make instant shifts.

At the end of the back straight we are right at 145-150. I can brake with him and maybe even get my couple of car lengths back, but it is clear I need to do 2 perfect downshifts back down to 3rd, get the breaking right, and turn the car in at the right spot. Coming off that corner we will be equal more or less because we will stay in third for two more corners, But the next time we need to make 2 or 3 upshifts the same thing happens. I will inevitably make a slow shift going up or down and if I do I can't get that time back. In 8 laps he's gone.

I intend to fix this with another 125 HP. We'll see how that goes.

But it will always come down to the driver in near-pear cars.

So will a GT40 kit car go as fast as a GT3, Yes. How?

1. 400 inch small block @ 500-550HP
2. 18-10F and 18-12 rear wheels running dot slicks
3. Correctly designed suspension geometry suited for the tires
4. 14 inch rotors in front and 12 in rear with appropriate calipers. All vented correctly. I don't think you need antilock brakes. BUT you will need to two-foot the car in the braking zone..................WELL.
5. Keep the car down to 2500 pounds or as close as possible. Leave ALL the bling off! Figure 10 gal fuel tank. You will use about 6-7 gals every 30-35 mins.
6. You will need to spend a lot of money on a modern racecar transaxle that can be shifted electronically and match downshift revs automatically with the engine management computer.
7. The car will need to run an efficient splitter and dive planes on the front and a large spoiler on the rear. Flat bottom the car as much as possible while running the car in a front-down attitude rake. I don't think you will need a wing. The total downforce on the front of the car can be balanced with a spoiler at the rear.

How much? If you don't pay anyone to do anything for you so the labor costs are near zero, you will have about $50K in the basic kit, $65K in the power train, $30K in the engine, and another $30K in the rest. About 175 grand if you run it in jelcoat and install one race seat.

Maybe you should budget for another 10 or 15K for................the other stuff. We all know how that goes. You will still be a lot under a Porsche.

"I intend to fix this with another 125 HP. " A quote from Jack Costella, holder of many speed records at Bonneville, "Add gears until you slow down... then add horsepower.":D
 
I've seen a Superformance with a 351 stroker (think it was about a 427...) on 17 inch wheels....on a 2.1 mile track with several 360's/430's, an F40, two new corvettes, a porsche turbo, a gallardo, and a diablo...among others. The Superformance was at the front of the pack for most of the session until locking up a wheel upon braking....then finished the session 3rd. I got the feeling the Superformance pilot was having to work really, really hard, but was able to keep up with (and pass) most of these other cars. This was a couple years ago, and is my only frame of reference for the competitiveness/speed of a good GT40 replica. Needless to say, I was impressed. The Superformance piloti was a long-time SCCA driver with several class wins in smaller displacement classes.
Would absolutely love to see footage of something like this. Typically you never would since they are usually in the vintage group.
 

Howard Jones

Supporter
Niel. It's not an issue with top speed on the straight really. It's more of the acceleration rate from corner exit to top speed. Those GT3s have 7 gears and I have 5. If we both leave the apex at nearly the same speed (approx 50). I need to make 3-4 and then 4-5 and hold full power until the brake zone. But those shifts are nowhere near as quick at the PDK in the Porsche. Additionally, their rate of acceleration is better because they can remain at the top of their power range better. Then in the brake zone, their downshifts are effortless as well and they have antilock systems so all they need to do is slam on the brakes and Mister Auto Computer does it all. The only way I think I can overcome this is to 1. get a better driver or 2. out-accelerate them over the length of the straight by 4-5 car lengths.

There are two long straights at COTA so I nearly double the effect over the lap. Of course, more power will always be faster elsewhere. Besides SBC's are cheap to build. I can build a whole new motor, and then sell the old one for half the cost to do it, for what it would cost to add 125HP to a GT3 Porsche and still run pump gas.

In the end, you gotta spend it on something, or at the end someone else will spend it on something.
 
One factor that may throw off comparison is if that newer mustang, for example, has a driver thats ran the course for years and the gt40 driver has only had a handful of track experience. Could be deceiving. Would be nice to have same driver in both. I still say the 1000lbs of weight has to make an incredible difference despite no abs and shift delays.
 
Also now a days, how can there not be some sort of standalone abs kit that can retrofit on a vintage car. Also the same can be applied for paddleshift 6spd that fit gt40. To me it's an insane platform with the weight and size compared to modern cars.
 

Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
As I found as a crew chief in the SCCA’s World Challenge GT Class, ABS Brakes are clearly superior but only for a while. The problem with literalky all ABS Brake systems I’m aware of, is that they cannot sense the temperatures of the rotors, pads and most importantly the fluid. The ABS Brake system will keep braking at the ragged edge only to the point of total failure. All else being equal - A good driver who knows how to manage his momentum via judicious use of his tires and brakes can, indeed, out drive a driver with ABS. I’ve seen it and done it. Once that fluid boils, it’s all over…. To my knowledge, FIA and SCCA have not allowed brake fluid recirculating systems like NASCAR uses.
 

Howard Jones

Supporter
Isn't this what we might need? Same internals but is configured for a car like a GT40. What do you get for the $30K............just the basic GRBX I bet.
 

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Or you can just buy this. There are also a LOT of equally quick, used LMP3 prototypes for sale for a lot less and equal to what it would take to build a modern equipped GT40 in the $100-200K range.

For me, you're asking the wrong guy. I love alot of cars but none come even close to the gt40. The ultimate in looks and package. Now adays I'm surprised someone hasn't made one with all modern components. Probably weigh it down too much.
 

Ron McCall

Supporter
You really can't compare a 50 year old car/design to a modern performance vehicle. It's not even close. Just my $.02 with my own first hand experience.
With enough power , huge brakes, sticky tires and a bit of aero, you can. The car in this video is a Shelby GT350 on sticky tires.

Ron
 
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