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Where to place jacks while replacing frame rails?


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Whelp,

 

I made my own frame rails,and making new floor board, which means I really don't need to flip the car over.

 

With that said, when I remove the floors and rails, how can I sufficiently and safely suspend the car?

 

My plan is to cut the floors, cut the old rails, weld in new rails, lay new 16ga sheet metal floors in (using the new rails as welding points, completing the floor, then going under the car to finshin securing the rails to the new floors.

 

So, where do I move the jacks to? The rear jacks are tucked somewhere over a cross member where the diff was, so that's fine, but the fronts are sitting on the rails, I was thinking I can run the jacks to the strut towers (car is bare frame by the way) but I'm afraid of sagging or simply not being able to support the front end.

 

Any ideas? How did some of you guys set it up?

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I'm guessing the motor and trans are in the car? If so, it'd be carefull but you can probably stick them under the front engine x-memeber for the front.

 

I did the exact same thing you did, cut the floors OUT and stuck in sub-frame connectors and floors all at once. I posted a thread detailing most of the work with some picutures etc...

 

When I did it, the interior and all mechanicals were OUT of the car, so it may be a bit different, but I didn't have any sagging issues using the points in the rear you are using, and the front point i mentioned.

 

Do a quick search on my user Id and go back about 3 years in this sub-forum, should see my posts. I used Pete Parasska's drawings from his site as inspiration.

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I'm not going to the same extent as you are, but I am looking at installing Bad Dog framerails (subframe connectors) and I want to be sure that their isn't any sag in the car when I do. I think that it's a fairly safe bet that 30 something year old unibody cars will have some sag, especially one's that need new floor pans and framerails. I did a simple test that I think indicates that there is some sag in my car (http://forums.hybridz.org/showthread.php?t=121536 toward the end of the thread). I think that moving the front jackstand position back allowing the weight of the engine to reverse sag before installing the frame rails is a good idea...of course that's just my opinion.

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Thanks Bill, I'll look up your thread momentairaly.

 

as mentioned, the car is just the frame, when I say frame, there isn't a bolt left to unscrew, or interior piece to take out. No gas tank,diff, engine,nadda. One big solid piece. (scroll to the bottomto see the rails/where I'm at now: http://forums.hybridz.org/showthread.php?t=119866)

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I don think you willhave any problems. Infact, if your rocker panels are whole, there is no reason for sag. the shell of one of these cars is amazingly light, so I dont think you will have a problem. although I could be wrong.

 

I would say to bolt the front crossmember back in and use that as a front jackstand point.

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Right now, I have my 240 apart just the shell, with the exception of the rear suspension. I have the rear tires sitting on plastic milk crates and the front is sitting on three stacked spare tires under the lower rad support. It is dead on level. I cut out one side at a time, as I progress with the frame rails and floors.

 

It's pretty cool to be able to lift the front of the car and move it around rolling on the rear tires!

 

The front crossmember has to be out to replace the front rails. I did reinstall the rear transmember to keep the tunnel in shape.

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I was just putting my shell+doors on my lift the other day.Its a 280z and without anything in the car whatsoever aside from the doors i noticed at least a good 1/8" change in the door gap upun lifting the car,i personally would be carefull,and this is why i am going to street cage it:)

 

Hrmm, you just made me think of something. I'm going to throw the doors back on when I do this. Might be an easy way to keep track of any changes, and adjust when needed,where needed. Good thought!

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I used jacks directly under the front of the rocker panels. the car is so light up front I can lift it with 1 hand so there is DEFINITLY not much weight to cause sag or anything of that sort. Plus the rockers are a much stronger point of the car then the original frame rails were!!

 

you can look on my site to see what i'm doing with my frame/framerails. Just click on my sig picture. (btw all my pictures can be clicked on... some odd reason not showing different mouse cursor)

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as mentioned, the car is just the framehttp://forums.hybridz.org/showthread.php?t=119866)

 

Sorry, guess I missed that!

 

I'm positive you won't have any issues then. My car sat w/ out floors for over a month, sitting on the front and rear x-members. My experience was that the Doors always stayed the same. I never measured the gaps but there was never had any change in the way they closed durring or after the procedure, and I checked them OFTEN!

 

Remember to check Pete's website for some really good detailed drawings.

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Thanks Bill! Next Friday I payday, gotta stock up on some more 16ga for the floors then these bad boys are on their way in :)

 

Hey Cable Srv, saw your website, got a couple q's on your frame rails.

 

I saw you used 2.5x.1.5. I'm not sure if it's different on the 240's ( I have a 280) but my front rails measured 2.5x2.5, then under the floors were 2.5 wide by 1.25 tall. Will having 1.5 tall front rails misalign anything?

 

Also, I saw you added some cross members along where the trans tunnel is Will that actually end up behind the transmission/under the drive shaft? I may actually copy that idea :) Just don't want to run in to any problems.

 

Any other tips appreciated!

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it will slightly on the floor. But if you look at pete's site his rails go above the floor itself. I plan to raise my floor by .25 inch due to this. I simply wanted stronger tie in's to the body and even after this is is put in place, I still have more to do. I plan to also weld 4 horizontal frames connecting the frame rails to the rockers. 2 on each side to connect the front and rear rocker to the frame. Then after I start my tube chassis, I plan to tie that and the front frame into the rockers.

 

If you do some search on this forum, alot of ppl have stated that the rockers are one of the strongest parts in the 240z unibody. Unlike the original frame rails which is sad... but hey doesn't bother me just means another area I need to tie my frame/tube chassis into.

 

as far as those cross members... in the trans tunnel those are only temporary atm. They were put in place to make sure once I welded the entire frame together as 1 peice that it kept the frame rails squared. Think of them as a jig for the frame. After the engine/trans gets put in the car I do plan to ad REAL braces to those areas tho. It's just I need to wait to see what clearances I have for that. And those 1x1 tubes currently your seeing... yea those WON'T hold much to stress!!

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