frame building ?

i am planning on building a frame for my truck and i was talking to a couple guys today about it. do i have to have a frame jig or no? what i was wanting to do is weld some 1x1 to the bottom of the stock frame and lay the 2x4 on top of the 1x1 and inside a few inches of the stock frame. will this work? i want to go from the firewall back. they are telling me that it will not work because the 1x1 will tweak when i weld it, so bad that i won't be able to lay the 2x4 down evenly and the frame will be uneven. i have never done this before so as much help i can get will be much appreciated.

I think it would be better to build a frame jig so you could make that perfectly level and build the frame off that and be easier than trying to work with the old frame. I plan on building one like this when I start my frame build:

Also is there any reason your using 2x4 tubing instead of 2x3? 2x3 will get you 2 inches of drop and is plenty strong.

if im understanding this correctly then lay the 1x1 down and tack them outside and middle. descent tacks. and go back inbetween those and then on and on until you have it on pretty well. and then lay the 2x4 ontop and tack and tack like before and then weld all up in increments of like 2-3 inches, keeping the steel cooler and less warping.

It could work, but you would have to remove all the crossmembers to do it that way. And there would be an odd joint at the firewall, would probably have to use sheet to make fillers. I'm saying this because the new frame will be narrower than stock and won't line up with the front clip. Something to think about. Good luck!

thanks guys. i think i am just going to back half it. i got everything pulled off last night, so now i just need to go buy some 2x4 and get to it. now what i have to figure out is where to mount the rx7 rearend. i know how to get the wheel base right but i don't know how high to build the frame. going to be interesting.

well if cut and weld doesnt work....cut and weld again.

i belive there was 11 inches difference fron the subframe mounts to the diff mounts.. i wont be able to check for a few weeks im headdin out on vacation...find a stock rx7 at the scrapyard and measure

hahahahaha tuchae!!

i am mostly concerned with how high or low the rearend needs to be mounted. if the pinion angle is all out of wack i am going to have to redo everything. i guess i will just have to do a ton of measuring.

rule of welding:

measure twice, weld once