Frame rail rust

[az240z]

I had this car painted about 5 years ago and it has sat outside, covered, since then. I have a 4" rust hole on the back of the drivers side frame rail. My question is should I replace the whole rail or just have it cut out and have some channel welded in. The rest of the frame rail is in good condition. The passenger side frame rail has no rust but looks as if it was used for jacking the car up. Here is a picture of the rust hole.

 

 

Any suggestions??

[pparaska]

If it looks like that there, it's probably almost rusted through most everywhere else.

 

I'd either do the BadDog rails, or if you really want to get into a project, see my solution (about halfway down the page) This is a bunch more work than the BadDog part, but if your floors, firewall, engine compartment frame rails are shot, well, why not?

[Marine1342]

Now my question on this pparaska, (we had emailed each other a while back, considering on doing the same thing) is the safety in this.

The engine frame rails, from the information I've gathered is 3 sided box with the 4th side that completes is consisting of the wheel well area.

 

I ] ----- [ I

 

Pardon my crude drawings.

 

You replaced it entirely with square tubing, measuring everywhere to keep alignment as close to original as possible.

Now my safety question is this:

 

What size thickness did you use on the square tubing, because the nice thing I can see about sticking with BadDog rails or even the front frame rails from Charlie Osborne of Zedd Findings is that in the event of an accident in the front, the thin metal will give way, whereas putting square tubing might just end up ramming the tube through the firewall and into your leg.

 

Am I wrong on the structural set up on the Z, maybe not planning on adding enough re-enforcement, or that's just the way things are?

[norstar]

Thats rust? grind it, treat it, cap it and move on. You west coast guys have no idea!

[pparaska]

Marine - good thinking there.

I used 0.093" wall tubing for the engine frame rails. Take a look at the photos on that page - I tied them to the subframe connectors in the floor very well, and I added a piece of 1/16" steel plate to the firewall where they attach, lowering the possibility of the engine rails "punching through the firewall. So if I hit something, it's going to bend at the firewall or at the T/C bracket, not come loose and into the passenger compartment.

 

But that's just my guess. I'm a mechanical engineer, but this is a gut feeling. No calculations were made on the stuff I did. ktm or someone other "real" structural engineer or chassis builder types can give their assessment - I'd like to hear it.

 

You have a good point there though. We need to be careful of making parts stronger than they were stock, the crush design changes. But I'm doubting that the 240Z designers put a bunch of thought into that way back when.

[ModernS30]

Thats rust? grind it, treat it, cap it and move on. You west coast guys have no idea!

 

Was thinking the same thing. thats a very small hole compared to what I had on my first z. I didn't even have the rails there.

[Marine1342]

az240z, if you're planning on keeping it stock then yeah just grind it treat it cap it. If you're doing and engine swap or even maybe increasing the engine power you might want to consider either re-enforcing the rails or extending them to the back frame.

Or if you're going to push for a v-8 swap then do as pparaska did and tie in all the sub-frames together.

Hopefully I'll start the front rail swap soon

[gnosez]

Pete's rail set-up is in my opinion the optimal set-up if you're plans for the Z include very high HP/torque and high stress inputs.

 

The Zeddfindings rails are a great example of an OEM replacement part and we recommend it to folks who plan on keeping their cars stock or don't beat on them even when they're not.

 

We designed the Bad Dog Parts rails as a third option and while they will not make your Z as rigid as Pete's design they are thicker than stock and also tie in the rail to the rear wheel well.

[Marine1342]

I know that BadDog's rails are meant to fit over the existing rails underneath the seat and ZeddFinding's rails are original replacement. So ideal set up would be Zedd Findings to replace and then re-enforce them with BadDogRails and sub frame connectors/extendors.

Now where would one go and get the front frame rails? I know you can do Pete's method of cutting out and replacing it completely, ZeddFindings has front frame rails as well. Are these the only two places? Does BadDog have any?

[az240z]

Thanks for all the reply's and I am planning to keep it stock. I realize that it isn't much rust but wanted to get some ideas. I like the idea of putting something over the existing rails and will look into that.

[mr jdm]

why dont you just cut out that bottom part of the rail and weld in a flat peice of metal and replace the rusted/cracked section?

[gnosez]

Bad Dog does not sell the front rails (only Zeddfindings does).

 

We try not to compete with Charlie ( a real nice guy who also happens to love Zs) so we saw no reason to expand into an area he had already covered.

 

You can order the floors from Charlie (240 or 280) and the rails from us as ours are made to fit over existing OEM rails or to act an a complete replacement.

 

For a stock Z, get Charlie's rails.

[cd1105]

I have the same frame rail rust spot but on the passenger side. I planned on just cutting it out and welding in another piece of metal, since it was only a small section.

[galloguy05]

So just today I found nearly the same hole in my frame on the drivers side. Can anyone chime in here as to how well just cutting out the bad part of the frame and adding in new metal and then treating it for rust prevention? Maybe just for a couple years even? Would this be a viable solution or is an entire frame rail replacement the only solution?

 

I plan on keeping the car under 300 hp at MOST with future plans realistically being around 220 hp or so and the car is currently stock (75 280z) besides shocks and springs and 5 speed. My floors and the rest of the frame are nice and not rusted, so I do not want (at this time) to replace the entire frame rails.

 

Thanks,

Matt