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luke87gt

Structural Reinforcement to Handle 500rwhp

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Hi guys... I have a pretty good idea on what to do when it comes to adding power to the 240z.

 

What I don’t have the best idea about is what structural integrity mods I should be considering to handle a 500rwhp 6.2L LS3.

 

Given that these cars weren’t designed with that level of power and given that the platform is nearing 50yrs old, i’d like to make consideration for this early on.

 

Any recommendations would be appreciated.

Edited by luke87gt

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The links jhm & calZ are great.  For a street car what I have found is that if you strengthen the frame rails then do some basic strut bars the car is plenty stiff for your needs and if you want to a bit more then do some further bars just for the  towers; this will avoid needing cage.  If you do want to race you would just need a hoop but for street there is no need.  I added some pics of my rails and others have done similar versions.  I did another 240Z where we found great boxed rails that were thinner and fully boxed so we just welded that on the bottom and eliminated welding inside the car; easier and similar result.  This way your car is more street and others driving with you will appreciate not being in a cage.  I own a more caged Z as well but when you get older you will find women often do not want to be in a caged car, maybe just a hoop but nothing more...

insidefloor.JPG

rear floor to rear frame2.JPG

seat area of floorboard.JPG

front wheel well frame.JPG

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Luke, I just noticed you live close to me; a great shop that can do all of the frame rail work and even some strut welding is Dando's Automotive in Fremont.  Ask for Ken they can do all of this and the price is extremely reasonable... PM me if you want more infor

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The thread cited in CalZ's post is indeed immensely helpful.  Unfortunately, the principal link with photographs, http://s160.beta.photobucket.com/user/psanders240/library/BSR-260Z-IMSA, is now broken.  The thread hasn't been updated in 3 years, since its main contributor (JohnC) died.  The original thread is from 9 years ago.

 

My own subjective belief is that the attempt to structurally strengthen the Z, while admirable and maybe eventually necessary, tends to derail (no pun intended) swap projects.  Do the swap first, and get it running, even if the chassis is floppy and inappropriate for the aggressive amount of power.  Also be mindful, as JohnC used to frequently observe, that suspension-loads are higher than drivetrain-loads.  That is, chassis flex is a greater problem for a stock-powered Z driven in a racing situation, with stiff springs and aggressive turns, than in a Z with quadruple the power driven on the street (or in drag racing) with unmodified suspension.

 

Also, if doing an aggressive engine/transmission/differential upgrade, almost invariably there will be metal cut, new metal welded and so forth.  This means new points through which loads are passed.  It also may mean that "conventional" approaches at strengthening the chassis can interfere with the swap-related mods. An example is the venerable "Ron Tyler differential mount", which was for the R200.  Would it work for the R230?  Probably not in "stock" form.

 

So... fit the engine, do the swap, get it running, and THEN worry about alleviating chassis-flex.  I speak from experience, because I did this backwards, worrying about the structure first.  Yeah, it's rigid etc.  And?... project has taken 20 years.

Edited by Michael

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I can definitely relate to Michael. Mine took 12 years to drive, although I took a couple years off. 

My suggestion is if you really want a done up chassis that's caged and ready to race, buy someone else's race car and start from there. If it's a street car I'd focus on things that are easy to accomplish and don't get too hung up on perfection. Things like strut tower bars make a big difference on a 240. Look at Apex Engineering's K member front crossmember setups, bolt in and connects the front X member to the TC rod buckets. Another simple area to brace is from the end of the rocker panel to the upper frame rail. You can pull the front fenders, weld those tubes in, cut the little piece that separates the fender from the wheel well, and bolt the fender back on.

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Strut bars

Tubular frame rails

Fender bars or front strut tower reinforcement

Front sway bar reinforcement

 

Granted if you plan on putting around and your stock floors and rails are good as Jmortensen says you could get away with quite a few off the shelf options. Once you start launching the car and moving to stickier tires and putting on harder suspension is when weaknesses are going to show.

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I'm right in the middle (nearing the end?) of this stage so I can share some pictures of some of these things. Read that chassis prep thread many times and would have benefited from some detail shots. Lots of great info though. It's taken me around 2 solid months to get to this stage, but I've been pretty lucky in the rust department. Still need to finish my frame rails and seat mounts.

 

 

 

 

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IMG_6483.jpg

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10 minutes ago, artishard116 said:

I'm right in the middle (nearing the end?) of this stage so I can share some pictures of some of these things. I read that chassis prep thread many times and would have benefited from some detail shots. Lots of great info though. It's taken me around 3 solid months to get to this stage, but I've been pretty lucky in the rust department. Still need to finish my frame rails and seat mounts.

 

 

 

 

C7CF3035-8570-46E9-954F-A939A770F218.jpg

E5C86342-F34E-4ECE-AD13-7A60EEE7DA5D.jpg

DSCF1626.jpg

DSCF1625.jpg

DSCF1624.jpg

DSCF1623.jpg

DSCF1527.jpg

DSCF1526.jpg

DSCF1538.jpg

DSCF1541.jpg

DSCF1523.jpg

IMG_6483.jpg

IMG_6625.jpg

 

Edited by artishard116

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I would also add the importance of removing the lead filler in the C pillar to roof seam and seam welding it for more strength. I have witnessed a friends 250ish hp L28et crack right through new paint in that area. I made a mental note and addressed it on my build. 

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2 minutes ago, Nelsonian said:

I would also add the importance of removing the lead filler in the C pillar to roof seam and seam welding it for more strength. I have witnessed a friends 250ish hp L28et crack right through new paint in that area. I made a mental note and addressed it on my build. 

Considered doing this as well, my original paint is showing the beginnings of cracking in that area. What’s the best way to remove the filler?

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Another issue is the primacy of class-rules.  Some very intuitively appealing things - by my reckoning - may run afoul of class rules.  One example is the business with the total included-angles in the main hoop.  Must be < 180 deg?  Consult the rule book.  And on a similar subject: can the hoop be welded to the surrounding sheet-metal?  If so, this ought to be of particular value in alleviating the aforementioned C-pillar stress concentration.


We should probably move this thread to the brakes/suspension/chassis sub-forum.... mods???

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14 hours ago, Michael said:

And on a similar subject: can the hoop be welded to the surrounding sheet-metal?  If so, this ought to be of particular value in alleviating the aforementioned C-pillar stress concentration.


We should probably move this thread to the brakes/suspension/chassis sub-forum.... mods???

Yes, the hoop can be welded to the surrounding sheet. I have some shear panels welded between the sides of the car just behind the door and the vertical part of the hoop, and a couple 4" wide tabs where I welded the map bar to the top of the hoop. 

I totally agree that this is the way to take care of the C (actually B since Z has no B pillar) pillar paint cracking. 20 years or so ago I had a friend who ripped the A pillar off of his 240 autoxing it. He fixed the A pillar and welded in a 4 point bar and added one 6" wide shear plate just on the top and that got rid of all the interior panel creaking when he would go into driveways. 

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