2+2 Chassis Reinforcement

[Twisted46]

My question is pretty basic, due to the body differences between the 2 and 2+2 S30 would you approach reinforcement any different for a track prep application?

 

Let's assume we are following the basic John C guidelines:

 

1. Seam Weld (every sheet metal seam overlap.)

2. Bad Dog Subframe Connectors

3. Weld-In Roll Bar.

4. Welded In Rear STB.

5. Triangulated Front STB.

6. Radiator Core Support Reinforcement.

7. Transverse Link Bracing Reinforcement.

8. RT Diff Mount.

9. Tubular Seat Mounts.

10. Box Upper Frame Horns to Firewall/Cowl.

11. Reinforce Pedal Box/Brake MC Mount.

12. Reinforce Front ARB Mount.

13. Reinforce Front Strut Tower to Frame Rail Junction.

[walkerbk]

The Bad Dog Subframe Connectors will be to short since it is a 2+2. I changed my frame rails out with 1x3 steel tube. The 1x3 is actually shallower than the original frame rails so depending on your power levels, 2x3 might even be a good idea. 

[Twisted46]

That is a good point, I bought my own steel for connectors. I also have bars that connect the front of the rocker/footwell area  back to the main hoop.  I figure the mid section of the +2s are probably more bendy due to the extra length. 

[Coelocanth81]

Bumping this thread. As a 2+2 owner, I'd like to see what you came up with. My chassis project is a few years out, but I'm looking for the same answers.

[Twisted46]

Sadly there is very limited info around about the +2s as they have never been popular but the little I have gathered is actually good news depending on how you look at it. Due to the possibility but unlikely event that someone would cram some victims in to the tiny back seat, Datsun had to up the GVWR which mean adding more heft which of course means more weight but also more strength in the center of the car. This will help if you are upping the power and launching the car a lot and reduce torque flexing but it still does not solve the overall issues of the chassis. you still need to focus on the same areas as the coupe and if you look at my other thread the single biggest improvement is a triangulated front brace. 

 

All that said if you end up doing a full cage like me none of this really matters and you are just starting with a heavier car. I did also add angle iron along the length of the rockers but mainly for jacking purposes. 

[primaz]

What I have found is that by upgrading the factory frame rail sections from the rear all the way to the front it works better than a cage which is great for using the car for street and track.  I had this done by Dando's Automotive in Fremont, CA.  Their first versions were using heavy gauge "u" shaped rails under and inside the car which mimicked the stock which was hard to even see it was modified.  The second Z we did there they found a boxed steel that was just welded underneath and that worked almost as clean without needing to weld inside.  FYI, I have a third Z with a 9 point cage and these other more stock street machine Z cars have a chassis in my opinion is as stiff if not stiffer without using a cage!  Also as proof my RedZ was on the freeway stopped in traffic and a Prius hit me at over 55 mph and the car was not totaled nor was the chassis bend bad at all and I survived, which I might not have if I did not do this frame rail work.  That is why I did it to my wife's Z, just purely for safety not for performance for her Z.

 

I included two pictures of the car after getting hit and one after fixing it.  If any 240Z got rear ended this hard without the frame rails it would be totaled and me the driver probably might not have survived or would be injured for sure.  The crushing of the rear stopped due to the rear frame rails being so strong.   I got pushed into the next car and was so pissed off but so glad for the frame rails as it saved my life and my car's life!

Edited December 26, 2020 by primaz

[Twisted46]

I agree that adding strength to the frame rails makes a big difference and is probably the best thing you can do to street car, but is not the only option that gets you the same results. It also only addresses a single issue with the chassis and those using a cage are probably already past the point of frame rails. It is a good suggestion for street cars.

 

However I do need to say for the safety of others that upgraded frame rails are NOT better or anywhere equal to a cage so please do not read this and think you can forgo a cage at the track. Apples and oranges.

[primaz]

Twisted, I agree that a cage is needed for safety for a track car.  What I do think is that for a street car the frame rail upgrades can achieve a lot of chassis stiffness that is better than many mild cages but not as much as a more extreme cage.  For the street it is good to me as you get more stiffness than just a simple hoop cage and strut bars and more than a cage with a hoop and even a diagonal bar.  I have another 240Z with a 9 point cage but not a full cage, it has a hoop that is welded also to the strut tower, a welded bar between the strut towers, welded bars behind the strut tower to the back of the car, a diagonal bar going to the passenger floor area near the tunnel, bars from the front towers to the center of the firewall and my other two 240Z's with the frame rails to me are about the same and possibly a little more as I can jack the car and have three wheels off the ground.  I was very impressed with what the frame rails can do without a cage but do plan on adding them to my caged car which is also a street car.  There are lot of people that do a more simple cage for the street and then you have more hassle for using the car on the street and the frame rails can do the same or more for chassis stiffness but they do not protect against a roll over or other types of crashes, although it did save me from the rear end accident thank god....

[Coelocanth81]

• I'll be building a street car - although, it'll see some "weekend warrior" track use (no class-specific racing).
• The plan is to seam weld, re-framerail, and 1/2 cage the car (braced main hoop and rear shock towers, door/rocker bars, a firewall dash bar, with bridged load paths from the front strut tower support - almost a full cage, minus A-pillar and roof bars for street safety. I want chassis reinforcement and safety improvements for a car that will be driven mostly without a helmet. The car will retain its full stock interior - with the exception of Recaro LX seats and front harnesses (maybe rear harnesses too, for laugh value).
• I'm considering a 9.2L LS-V12. HP is in the neighborhood of 750, and 600lb/ft of torque.
• The 2+2 definitely seems to be a red-headed stepchild. I'm discovering differences between it and the coupe that I never anticipated.

Edited January 3, 2021 by Coelocanth81

[primaz]

22 hours ago, Twisted46 said:

I agree that adding strength to the frame rails makes a big difference and is probably the best thing you can do to street car, but is not the only option that gets you the same results. It also only addresses a single issue with the chassis and those using a cage are probably already past the point of frame rails. It is a good suggestion for street cars.

 

However I do need to say for the safety of others that upgraded frame rails are NOT better or anywhere equal to a cage so please do not read this and think you can forgo a cage at the track. Apples and oranges.

 

Twisted, One other bit of information that I wanted to share as I know many people are using the Bad Dog parts but what I did was have Ken at Dando's Automotive in Fremont, CA whom did their own versions which I feel is way better than the Bad Dog which is not fully boxed.  Their first version was done on my RedZ 240 where they mated two heavy gauge steel U shaped pieces that are just a bit wider but not by much more than the stock Z rails and by welding an inside and and underside piece they form a fully boxed rail that appears stock if you are not a Z freak.  On my wife's orange 240Z they used their new design which is a fully boxed heavy gauge steel rail that is welded just on the underside.  Either way that creates a fully boxed frame and that I believe creates a stiffer setup than the Bad Dog non boxed rail.

Edited January 3, 2021 by primaz

[primaz]

42 minutes ago, Coelocanth81 said:

• I'll be building a street car - although, it'll see some "weekend warrior" track use (no class-specific racing).
• The plan is to seam weld, re-framerail, and 1/2 cage the car (braced main hoop and rear shock towers, door/rocker bars, a firewall dash bar, with bridged load paths from the front strut tower support - almost a full cage, minus A-pillar and roof bars for street safety. I want chassis reinforcement and safety improvements for a car that will be driven mostly without a helmet. The car will retain its full stock interior - with the exception of Recaro LX seats and front harnesses (maybe rear harnesses too, for laugh value).
• I'm considering a 9.2L LS-V12. HP is in the neighborhood of 750, and 600lb/ft of torque.
• The 2+2 definitely seems to be a red-headed stepchild. I'm discovering differences between it and the coupe that I never anticipated.

 

Are you talking about that Race Cast LSV12? I think it has that cool factor being a V12 and does use LS engine mounts, but that I believe is a cast iron block, so why not get an aluminum block LS instead as you get the same horsepower & lighter with much more options in parts, etc.?

 

I am all for cages but the reason why I mentioned what I did on my mild street Z's is that to me it gets the chassis stiffness without the need for a cage which is good for a more street car.  Your significant other will typically not like being in a car with bars all over and if they have to climb in or over bars that car will  only be driven with you in it and sometimes that causes people to sell the car unless it is for the track and they have the funds to have a lot of cars.  To me for the street you really only need a cage if you want to track it and the rules require that or if you are going to the extreme and the car could roll, etc. due to crazy speeds or extreme racing.  I do have one street car that does have a semi-cage because the goal is over 200 mph on the street yet I did not go all the way as I did not want to go over the line and make the car impractical for the street, which is easy to do.  You car sounds like a cool build but be careful not to go over the line as it sounds like your car is like my cars primarily street.

Edited January 3, 2021 by primaz

[Coelocanth81]

1 hour ago, primaz said:

 

Are you talking about that Race Cast LSV12? I think it has that cool factor being a V12 and does use LS engine mounts, but that I believe is a cast iron block, so why not get an aluminum block LS instead as you get the same horsepower & lighter with much more options in parts, etc.?

 

I am all for cages but the reason why I mentioned what I did on my mild street Z's is that to me it gets the chassis stiffness without the need for a cage which is good for a more street car.  Your significant other will typically not like being in a car with bars all over and if they have to climb in or over bars that car will  only be driven with you in it and sometimes that causes people to sell the car unless it is for the track and they have the funds to have a lot of cars.  To me for the street you really only need a cage if you want to track it and the rules require that or if you are going to the extreme and the car could roll, etc. due to crazy speeds or extreme racing.  I do have one street car that does have a semi-cage because the goal is over 200 mph on the street yet I did not go all the way as I did not want to go over the line and make the car impractical for the street, which is easy to do.  You car sounds like a cool build but be careful not to go over the line as it sounds like your car is like my cars primarily street.

 

The Australian "LS" V-12 is indeed the one I'm eyeing. I'm looking at the aluminum block option, which has a slightly smaller displacement (9.2 as opposed to 9.5). All told, I think it weighs around 650lbs, fully dressed. Definitely heavier than an alloy V8, but on par with the DOHC turbo inline 6 offerings - so I'm not too worried about the weight. Besides, I'm reaching an age now where I'm more interested in air conditioning than in shaving off all the fat. 

 

As for the partial cage, I think it's mostly for peace of mind. The idea of a side-impact on that chassis terrifies me. Secondly, having length-wise tubular structure that's  triangulated to the car's floor rails would create a "box frame" that's 18 or so inches high - bracing the tops of all 4 strut towers. I liken it to the biplanes in WW1. The upper wing wasn't necessarily for more lift - it was there to create a stronger structure by bracing it to the lower wing.

 

For what it's worth, that's the logic behind my thoughts.

Edited January 3, 2021 by Coelocanth81

[primaz]

The V12 will be a head turner.  One thought on the cage as it really is for safety as you can get the stiffness with frame rails and strut bars; you can have the door bars swing out and there are spring activated locks for roll bars.  My cousin did this on his hot rod so you have the side protection but still enables easier access.  People forget that yes they are ok with climbing over bars but most others are not  

[Coelocanth81]

On 1/4/2021 at 2:54 AM, primaz said:

 People forget that yes they are ok with climbing over bars but most others are not  

 

Very true...

 

When drawing the lines on functionality, the margins get pretty slim when door bars and multi-point harnesses come into play. I'll leave factory seatbelts in place for convenience, but I think I'm going to try to keep some type of welded door bars in the picture. My thoughts are that if someone won't/can't enter the car because of the door bar, then it's not the car I should be giving them a ride in - door bars or otherwise. I'll have to reserve the Datsun passenger seat for those who are excited by it. For everyone else, I've got a comfy daily driver that'll do just fine.

[primaz]

I would recommend options like this, if you must have door bars, as these will allow the bar to swing out and are spring loaded making it easier than pins, etc.

    http://www.1962to1965mopar.ornocar.com/mmo102002.html

I would also try not to go crazy on the bars as you can try to limit bars around the passenger area. 

 

There are also retractable 3 point and 4 point seat belts or just do 5 point harness on the drivers seat.  Believe me most women do not like seats with 5 point seat belts nor do they like any bars near them as they are worried about being hit by them, etc.  You also should consider more comfortable racing seats like the Recaro and look at their Comfort series or Dynamic which is more race but still reclines; spend more on seats that are leather, recline, adjustable and comfortable.  There are a few brands that can do that and have handle a 5 point belt but not many.

 

 

Edited January 6, 2021 by primaz

[calZ]

3 hours ago, primaz said:

I would recommend options like this, if you must have door bars, as these will allow the bar to swing out and are spring loaded making it easier than pins, etc.

    http://www.1962to1965mopar.ornocar.com/mmo102002.html

I would also try not to go crazy on the bars as you can try to limit bars around the passenger area. 

 

There are also retractable 3 point and 4 point seat belts or just do 5 point harness on the drivers seat.  Believe me most women do not like seats with 5 point seat belts nor do they like any bars near them as they are worried about being hit by them, etc.  You also should consider more comfortable racing seats like the Recaro and look at their Comfort series or Dynamic which is more race but still reclines; spend more on seats that are leather, recline, adjustable and comfortable.  There are a few brands that can do that and have handle a 5 point belt but not many.

 

 

How do these bars latch? The spring looks like there isn't much room before it binds, so if it's a sleeve style latch, there won't be much throw or interface of the tubes. That would worry me. 

[primaz]

My cousin used those on his caged Maverick, they work great.  You just push it down and it disengages the bar so you can slide it out and when they are put back in place they just pock up and locks.  They are plenty strong.

 

 

[calZ]

Plenty strong is a matter of opinion. I wouldn't run a bar in my car that wasn't at least pinned. 

[Twisted46]

I agree with what is being said. If it is a street car stick with the rails and box up the front end. A cage has no place in a street cruiser. Cage it up if you are headed to the track.

[gnosez]

Not all 2+2s had longer rails but rather different floor contours