framerails/subframeconnectors tell me what you think

[jonnymrp]

I am working on restoring my 76 280 in to a racecar probably to be used in solo events and other track events. I’m just finishing the tare down process Last weekend I finished building my rotisserie and got the car up with the help of my dad. now that I am able to get at the bottom of the easy taking off the sub frames was easy about 20 min with rattle guns and two people ripping and tarring. Next step is to attack the rust the frame rails on the car are not grate and I’m replacing them.

 

 

My design so far is to keep the bottom of the rocker panels the lowest point of the body. The stock floor and frame rail/sub frame connector hang down quite a bit I want to put a 1X2 square tube inside the rocker (reasons for that are 1 quick jacking and hoist points and 2 strength) I want the frame rail connectors (made of 2 ¼ X 2 ¼ 3/16 wall square tubing) to share the low point of the rocker panels (reasons for this is 1 can put the car down lower 2 maybe a smother bottom of the car would encourage air to escape with less resistance) now my question is if I mount my floor on top of my new relocated frame rail should there be any real problems other than modifying the pedals. I also need to replace the frame rails in the engine bay with 2-¼ X 2-¼ 3/16 wall square tubing. this would involve removing and reinstalling the bracket for the thrust arm. is there any tips on how to do this other than measuring from every direction.

 

 

Sorry no pics. But if you were able to follow all that I would much appreciate hints tips criticism. if any one has pic. of home build frame connectors I would much appreciate seeing them. pretty much I am confident I’m my self and my buddy Dave (who I am building this car with) to proceed with the design proposed and get all measurements correct. I just don’t want to hear when its all said and done “you should have done it this way†“ you could have done it more like this†pretty much before I go and cut my car to bits I would like some input. for beater ideas.

 

 

jon…

[JMortensen]

Your tubing is WAY thicker than it needs to be. 1/8" wall tube is thicker than necessary. Also 2 1/4" tall frame rails with the rail inside on top of the floor sounds like they'd be in the way of your feet.

 

You might want to start by searching for subframe connectors. Lots of people have done them with 1x3 tube, and lots have used 2x3 tube. The ones that use the 2x3 usually cut through the floor and have some of the tube inside the car so that it doesn't hang so low. Search for pparaska, then click on his link to his website. That has a LOT of good info about subframe connectors.

 

The "thrust arm" is a TC rod (tension/compression). I have a thread from maybe 2 weeks ago outlining my plan to modify the TC rod box. You might do the same for a full on racecar, or if you're not going that crazy you could just cut the box off then weld it back on when you're done with the frame rails, or make a new box as some in that thread have done (74_5.0_Z has some pics of his setup that might help).

 

Good luck with your project. Use the search function. Lots of good info on subframes and suspension stuff here.

[260DET]

Square tube can be handy stuff but the problem in using it as you propose is to attach it effectively to the existing body. It should be ok to run along the bottom of the sills/rockers if its sits along the pinch weld there, so it can be welded in both sides.

 

But flanged open channel is better stuff to use against a flat surface such as a floor, because it can be stitch welded along both edges and plug welded through the flanges as well.

 

But as Jon said, there has been lots of discussion on this subject already.

[Jeff]

This has been discussed quite a bit here but you can see what I did here. Warning that link is not dial up friendly.

[Mikelly]

I suggest you go to http://alteredz.com/structuralmods.htm and download his blueprints. From there, I'd go back and re-do your plan based on those blueprints and instructions. You can see pics of his frame rail design on my car at

 

http://photos.yahoo.com/dat74z

 

Dig through the various folder. But I'm with the others. You're using way to thick a material and you do NOT want the rail full inside the pan. It will get in the way of your feet.

 

And after looking at Jeff's link, He pretty much did what Pete designed in his AlteredZ blueprints! Jeff!

 

Mike

[turbo_fb]

The main reason for people chanign their front framerails is cause it makes the front stiffer right?

 

 

My Z has no rust on it, but since I am fitting an RB25 engine, would it be nesecarry for me to change the framerails ?

 

[Ed260Z]

The main reason for people chanign their front framerails is cause it makes the front stiffer right?

 

 

My Z has no rust on it' date=' but since I am fitting an RB25 engine, would it be nesecarry for me to change the framerails ?

 

[b'][/b]

 

Most people change their framerails because they're rusty. If your rails are good, just put in some subframe connecters.

[BWRex]

Nice link Jeff.I'm at the roundabout same stage,and it's cool to see someone at the basics,dirtywork part.(check out my member gallery,and you'll see what I mean)Keep the photos coming!