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I did a search and I read a lot of topics about it but they are all closed, so I allow myself to open a new one.

I will install a more powerful engine, +/- 450 HP, but I will never ride with slick tires on tracks with the car. So I think I'm going to increase the flex stresses, because the torque between the transmission and engine mounts increases during accelerations and the front of the car is more likely to lift, but not the torsion, is this exact?

I think that to increase the flex strength of the frame, I could weld a 40x27x1.5 mm steel tube all the way along the car under the rails. The only drawback I see is the slight reduction in the guard on the ground.

As I have to replace the rocker panels,I also think to weld a longitudinal reinforcement all the way inside.

I will complete by installing a lower strut bar inside the engine bay, above the transmission and crossmembers between the attachment points of the lower rear arms.

What do you think?
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Please keep in mind for the future that if you or any other member wish to respond to a closed topic, all you have to do is to PM me and let me know which one, I will gladly "unlock" the closed topic upon request.

I've always felt that if I were to undertake designing a rear "brace" for the Pantera, I would use the brace from the Maserati Bora as my starting point. See the picture below. Also notice the "substantial" brace which ties together the upper shock absorber mounts.


Images (1)
  • bora_engine_bay
FWIW, I agree with George: the real weak spot in the Pantera monococque body/chassis is the huge deck lid opening. A Swedish owner found this by cutting a plastic model open where the deck lid was, then twisting it, compared to a 'solid' deck lid. You can also do this with a cardboard box; one with a 'decklid opening' will be markedly more flimsy. Cross-bracing the huge rear opening seems to work.

In case you're wondering, the front end is fairly stiff, partially braced from the shallow all-welded front trunk floor.
Hi Rene
X-brace is a good idea for front and rear so the axles stay in place!

But the weakest point is the roof line there is so little metal. When you accelerate and brake the back end of car body is moving so its pushing and pulling the roof and therefore the cracks in A -pillars and where roof and rear wings met !
I have no good solution to prevent it other than full roll cage. I have now tried to reinforce roof line and A-pillars and inside rear wings on my new build, But don't now yet if it helps
Last edited by kimk
I well understand that the real weak bridge is the roof and pillar A and that the only good solution is a roller cage but I want to make a street car and keep the original look.
By stiffening the lower part we reduce the stress on the roof, as for convertibles and it's better than nothing, in fact my question is are there drawbacks to weld a tube under the rails that I would not think?
I thought about this too.

Triangulating everything is probably a reasonably accurate description of what is done with a full cage.

In the Pantera the spot that needs a cage is right where the decklid is.

You need to first reinforce the roof. With a roll bar mounted in the cabin that puts the roof reinforcement in about the right spot. I think inside the engine compartment would be better but makes it less accessible if you need to remove it. The bar needs to be tied to the roof.

Then you need rearward braces like the Gp4 cars have BUT the 45 degree diagonals would need to go through the decklid. If the car was a fastback, then that would simplify it, but it isn't.

Everything else is just a compromise of sorts.

Even if you were willing to accept the engine mounted roll bar and rearward braces down from the roll bar, if you look at virtually every car that has the rearward braces, you take up the space that the decklid struts occupy in a street/production car.

The race cars use a prop rod to hold the decklid open.

Long ago (late '70s) I noticed that every Pantera that had it's paint stripped off and was repainted had cracks in the paint in the roof pillars. In investigating this further, I found that the cracks were only in the paint, not in the metal.

I guess the original PPG paints used were flexible. The replacement paints were not.

The rear uprights in the Pantera probably should be X'd like the front frame on a 427 Cobra is.

I just live with the "Pantera" cracks in the paint like the 289 Cobra people do with the cracks under the doors. It's just part of the cars quirks.

I don't think you can eliminate the chassis flex, just reduce it. It depends on how much effort you want to put into this BUT if the criteria is to keep the car stock looking, that's not going to happen. It's going to look like a race car. Or worse, like a Baja race car.

Everything from the firewall back is just like a diving board.

Take a look at what Comp2 did. His solutions help are creative and reasonably effective.

I think you probably can dial them down a little but making the stiffening attractive or aesthetically pleasing is a challenge and also just a matter of taste?
Hello Gents, let me fill you in on my mods. #1387 I made a full perimeter frame from 1"x1-1/2" tube. tied it to two full runs from Rad. support back to the eng. bay along side the console with cross braces. New floor pans of course. it gets tight back there but doable. cant drop the oil pan anymore. cross bracing thru original frame into lower A arm mounts and radiator support replaced with this tube also. A pillar and B pillar plates added inside cab and eng bay. Additional cross bracing at upper rear A arms. Car is slammed wide body but still has 4"front and 4-1/2" rear ground clearance. Cannot even see the mods unless you know what your looking at. Running a 410 Cleveland with all the upgrades making more power than the ZF can handle. 335/35/17s 14" Wilwood brakes ect. Yes a lot of work but well worth it! car is a rock at 2800lbs

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