I need to do some some repairs/patch's on my frame rail around the K member...What gauge/thickness metal is correct? In researching this I have come across suggestions of 11 and 14ga steels. I have used 14ga steel studs on many construction projects and although quite strong. I'm not sure if that is the case here.

Cut a piece out and measure it

I can do that but I was interested in what the peanut gallery thought.

There's the problem right there, you're confusing thought with knowledge! Generally you'll get ten responses of the former to every one of the latter.

You can go thicker. Put the "fat" side in and weld and grind and no one will know its stronger than it should be. Good luck.

12ga, 11ga, and 1/8" are commonly used for frame repairs. any of those that are easy for you to obtain will work for what you need to do.

I find it easiest to find a section of rail and cut out what you need... then you can go to the factory spot welds and so on. Plan on replacing further than what you may think. Also not an area you want to leave weak by not replacing enough.

That is what I'm talking about Stanton. Silver 70...hard to find a piece of that rail so I'm going to use some 11ga metal which is actually 1/8". I can pick it up at the new Tractor Supply that just opened nearby...I love that place. Thanks guys

Well stock frames are nowhere near 1/8 thick. If you need to match a stock bend - good luck doing it with 1/8. Personally, I'd match the gauge, cut out whatever needs to go, flange those edges to accept the new piece and weld it in. The flanges will give backing to ease the welding process. If you don't have a flanging tool, screw or tack a backer strip in behind each joint to yield the same result. The nice thing about the stock gauge its its easily formed with some really basic tools, scraps or blocks of wood.

You will find most Mopar frame rails are stamped from 18 gauge metal. In locations where extra reinforcing is required, most of the time a 6" long additional 18 gauge piece is spot welded inside the 1st piece. In areas of extreme stress, a 3rd layer of 18 gauge may be spot welded to the outside. The only place I've seen 14 gauge is places like seat belt reinforcing or areas where adding a 3rd layer of 18 gauge is not feasible. Some of the "newer" cars use 14 gauge reinforcement instead of tripling up the 18 gauge.

Things like K members started life out as 11 gauge before the parts were stamped out. Most of the "real" frame, or subframe boxes are 11 gauge.

When you come to my welding shop for a frame repair, you will get an 11 gauge patch. Gene

This is not a concourse or numbers matching car so "form follows function" as they say but I do want it to blend in. As I said I have used structural studs for years and they are good alternative to frame repair as they are already bent. I could probably use them in a case like this but the area that is being repaired is from the from the middle of the K member, including one mounting point and fades forward into the front bumper mount, the extra won't hurt so I'm going to follow Genes advice and stick with the 11ga metal.

I bought a repair cap from Auto Rust Technicians.

Auto Rust Tech has good parts, I've installed many, could be excellent solution for you too.

I thought body panels were 18 and frame rails were 16? If you use 16 gauge for your repairs, you will meet or exceed OEM thickness. 1/8 would be way overkill. Only time I ever use 1/8 would be patching truck frames.

I have measured various body panels when making patches. Frames seem to be in the 18 gauge range. Body panels seem to be closer to 20 gauge. The problem getting good thickness measurements is that as the panels or members are formed, the metal will stretch and shrink into various areas. So there will be some variations. But this is what I get when measuring with my micrometers.

You can use 16 gauge if you wish, but what are you going to do when you reach a point where there was a reinforcing piece inside? The 16 gauge isn't as strong as 2 layers of 18 gauge. Also, the original factory frame relied on the frame flanges and a good floor pan to reach its strength level, how is your 50+ year old floor pan doing, is it just a little weak? 16 gauge is pretty tough to work with (14 gauge is worse), its too thick to cut with hand held tin snips, and its pretty difficult to hand form. You have to buy 16 gauge in sheets, so everything has to be cut to size. 11 gauge can be bought in specific widths, as well as in box and round forms. 11 gauge is actually easier to work with. Often 2" x 3" 11 gauge tube slips inside the original frame rails. Its a lot easier to get a good weld on 11 gauge then it is to get a good weld on 16 gauge for most non-pro welders.

I can drill a hole in the bottom, and cut an access hole in the side of a 2" x 3" 11 gauge tube to install a nut to bolt up a K member and not be concerned about causing a weak point. You can't do that with 18 gauge, or 16 gauge, or even with 14 gauge. Build your frame repair pieces with whatever you choose, I'll do the ones I do with 11 gauge. Gene

What model car is it?

Its a 69 Satellite, I'm taking out a 318 and putting in a 383. I looked at the caps...they seem pricey. I just need the end out to the bumper which is all straight. I will have to weld in a the K member nut which could be a "pita" with lite gauge metal. I like the tube idea...cut the bad end off, weld the k-member nut on tube, drill some holes for spot welds in the existing frame, slip the tube in, put a few spot welds on all sides to hold it in place. I could finish the bumper end by fabbing some lite gauge metal like OE to cap the tube, weld the connection and finish it off the same way with some spot welds to the tube. I think that will work...

Looking at 71Charger's post it looks like I may need to weld in a couple more nuts for the bumper brackets, but that should be a problem...measure 20 times and weld once. I find making a little template always helps too

Save yourself a bunch of trouble and just buy a good used frame rail. Cut off what you need and weld it in. Too much dicking around welding nuts in etc.

I've used both, Auto Rust frame caps and used frt rails. If not overly concerned with appearance, caps work great.

Further investigation reveals that someone has attempted to make some half assed repairs on the inside of the frame rail. The inner fender as I guess it is called and the top of the frame under the battery tray is pretty rusted as well and will need some work. From the looks of it a cap or a new piece of repop frame rail will probably be the best course of action. It's a bit of a mess but I'm looking forward to the challenge

If the inner fender is rotten as well - common around the battery tray - why not consider replacing that whole frame rail and inner fender with a good used one.

Cut the spot welds out down the rad support
Cut the spot welds out at the firewall bracket
Cut the spot weld out on the cowl bracket
Cut the spot welds out along the floor
Cut the spot welds out at the crossmember
Using all those holes, align and weld the new section in

That is what I'm thinking. I see a couple of Moparts members are offering the frame sections, I'm still looking for the inner fender. That really seems like the way to go, but I'm pretty stubborn. The asking price for the material; used is about $400...not including shipping. The re-pop stuff is $500/600 depending on the quality and supplier. The frame cap is around $300 with the shipping and the patch section is fairly flat, although it has an indentation in the battery tray area, to make some extra room for the battery...which may or may not even be necessary. I'm thinking I may be a able fab something up for that. Once I get the steering column, motor and suspension out of the way I can get a better look at and then decide.

Post a "want" ad - I'll bet someone steps up with what you need. In the ad say where you are and would like to find one close enough to pick up. Ya never know !!

That is what I've done. I've picked up quite a few parts for my project thru Moparts. I would rather support our friends in the "community" whose knowledge and support are indispensable.
Thanks Moparts