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Hi, hopefully this is the right spot to post this question. i have a 71 240z that I am restomoding. I also have a close to 600hp ls3 dry sump engine . if anyone has experience with that much hp in the 240z, what would you recommend to stop it from twisting? I have a full roll historic roll cage. Front and rear strut braces. what else should I look to do?

I have several 240Z's. On one I did a 9 point cage consisting of a custom hoop with diagonal bar to the front passenger area near the tunnel with bracing on the rear towers and bracing for the front towers. Then on my other more mild 240Z I did a heavy gauge "U" channel frame rails under and inside the car covering the factory fake rails that went to the rear towers and all the way to the front of the car. What was amazing was that my mild 240Z solved the chassis twisting and was stiffer that my 9 point cage 240Z. I also had a rear end crash where I was fully stopped and a Prius hit my mild Z at 60 mph and only the rear end had damage, the car from the rear struts to the front were totally fine and so was I! That saved my life and the car was fixed with no issues. I also love that you have to be a real Z geek to even know it is not stock as the rails are just a little taller than the stock rails that they cover up so it looks like the car came that way from factory. Thus I would say frame rails but NOT the ones available at all of the companies I have seen as they are not that thick. The ones I used were strong enough where just one "U" channel not in the car would not bend even when you stand on it. Also my mild Z with the rails was stiff enough that you could jack the car and have 3 wheels off the ground so it was way better than the cage. I am adding that same "U" channels to my more extreme 240Z with the 9 point as I am installing a 750-900 HP RB30 turbo and the car will be a reliable 200 + mph 240Z.

having just completed my first HPDE track day in my Z a couple weeks ago. I 10000% recommend at least trying one. Local clubs vary but cost to seat time to fun ratio is quite high. you dont need to have a track weapon. you don't need to be a professional driver. you just need to have fun.

@Joe0690 you don't mention if this is a race car or a street car. I'm guessing since you're talking about a 8-point cage this is more race car or dual purpose with a heavy emphasis on the track part. A friend had a 550 HP LS-2 powered 240 that we made a lot of changes to to stiffen. The normal cage will need some additions to really help make the car stiffer. Frame rails that everyone adds are fine for street cars but are not going to give you much in the way of gains compared to adding additional tubing to the base cage. The triangulated strut bar needs to connect to an additional cross bar that hooks into your cage and is sandwiched under the wiper cowl are where all the metal comes together. This can then be plug welded through the firewall and is triangulated into the existing cage's cross bar. The next big change would be to add X bracing on the floor between the roll hoop and front cage legs. The floor of a 240 is very week compared to a modern car. This weighs about the same the frame rail mods but will add more in stiffness. There are a number of other areas you can add if you need more stiffness. In the stickies there are some examples of how most of these were done on various members cars. Cary