Frame repair on a '49

This is a typical problem for this support on stepdown - you'll notice even in your pictures the section has tons of crud in it.

LOL - it's one of the only areas on my 49 that didn't need a rust repair!

Your's cracked at the weld because the weld orignally thinned the area on the edge by microns - but the rust out from the inside caused it to weaken and crack.

I'd take that gusset - widen it so it drops down to the flange where its pinch welded.

Then not only weld completely around the perimeter of the new piece - I'd drill some holes in the gusset and the plug weld those to the original pieces remaining.

Here's a sample from the center section mods I did on my 49 - I used 3x4" thick box tubing, cut in on edge and slipped it down over the cut-out section - then welded around and to the flange as discussed above.

lsfirth wrote:

Great input! I thought about a larger piece to fit down over the beam section, but never thought about plug welding it.....that would certainly help! Dan it looks like you really chopped down your height under the tranny/bellhousing. I imagine this was to gain more clearance....I'm wondering if I'll need to do the same modification or if I could just have my engine/tranny sit up a little. Did you really use 3/4" material?? Wow...I guess you did reduce the height a bit though too. I was planning on cutting the gusset out of 1/4" box tubing....maybe I'll go a little thicker.

Yes, whatever I do on the passenger side I was going to repeat on the driver's side to keep it looking original and balance the stiffness of the subframe attachment from side to side.

Much thanks for the input......I appreciate the help!!!
Lee

Hi Lee,

The 49 is setup for a 454 and TH400. the additional clearance gained is for the transmission and exhaust routing.

I used 3" x 4" square box tubing and the cut it lengthwise to get the "cap" section I welded in over the area I cut out.

Under the "Restoration->Chassis" links on my website theres tons of pics that show it in more detail.

Yes, everywhere I look the frame has crud in it as you noticed. Luckily it came from a very dry area and thus, eventhough the frames are full, the dirt is dry and there's very little frame rust. Any advice in getting the crud out of there? I was envisioning stuffing the pressure washer nozzle into every opening and blasting it until no more crud comes out. Then once it dries trying to get some sort of rust inhibitor inside the frames.....but that might be impossible????

Yep, air. high pressure water - then repeat until your're happy!

There are rust inhibitors and applicators you can use later on - Go to Eastwood Tools and browse around for undercoating.

The big thing to remember is - fix what you can structurally and such.

Even dipping and/or sandblasting will not get everything and once rust starts in the pinchwelds you can't get at it with any method.

Basically do the best you can as the problem with these old cars - and unibody construction in general - is that once the rust starts all you can do is try to stay on top of it over the years.

Dan