47-55.1 Welding MII boxing plates

[whitedog76]

Ok, is there a particular welding method that works the best? I have the boxing plates tacked in, cleaned up. The transmission/bellhousing crossmember is still in place as is the front radiator support. I have also added a piece of angle iron across where the steering gear was, fastened with 1/2” bolts.

So, is it better to start in the middle and work outwards? Or end to end? Work top, bottom, top, bottom? How about side to side?

From a personal standpoint, I’m thinking of only doing one side at a time and letting it cool in between.

I’ve also seen where it is recommended to install the crossmember before final welding. Since I’ll be laying on my back and I’m not a small guy, that doesn’t seem feasible.

I know it’s hard to come back from a warped frame rail. Am I over-thinking it?

[dsraven]

first ensure the frame is straight, square and not sagged
fit up the boxing plates like you want them, keeping in mind that if you plan to smooth the welds out so the frame looks like it was made that way, then you will need to leave the boxing plates a bit shy to allow for the thickness of the weld.remember if the plates are fit inside the frame rails, so you get more of a corner weld, the actual distance between the frame rails will be less, so the new cross member may not fit without trimming
clean the frame and flap disc the area where the weld will be. this will make a nice clean weld possible and keep the chance of burning oil, grease etc behind the boxing plates down
tack weld the plates in how you want them
weld small areas to keep the heat down. allow to cool completely before welding again. it is best to do both sides at once because when one side is cooling you could weld on the other side while the first side is cooling.
grind the end of the weld before adding a new stretch of weld, if mig welding cut the wire so you get a nice clean start.if arc welding ensure to chip off any slag and, again, quickly grind the leading edge where your weld will continue

[mr48chev]

Runnig short beads and letting it cool off in that area is the important thing as he said above. Anytime you get carried away with running long continuous beads you stand a real good chance of warping or distorting the metal you are welding.

[whitedog76]

So what you’re saying, this is about a 6 beer job? Weld a little, drink a beer, weld some more.

I’m planning on starting in the front and working to the rear in about 6 inch increments. My way of thinking is the frame is thicker at the rear, so less likely to warp.

I have a 3600 truck, so the frame is thicker (3/16 vs. 10 gauge) but I still don’t want to screw it up.

Anyhow, I thoroughly cleaned and degreased it. I used a whole can of engine degreaser and 2 cans of brakleen, trust me, it needed it.

The plates are tacked in right now. I test fit the crossmember and there was about a 1/2 gap, so I’m going to add some metal to both sides. I suppose there are variations between crossmembers and trucks. Anyhow, I have some 1/4” plate, so no big deal.

Thanks for the help.

[dsraven]

if you have a 1/2" gap on the cross member and you're using 1/4" plate for boxing, you could weld the plates in proud of the frame and be right on. bevel the edges of the frame and the boxing plate and that would give you a nice groove to weld into for good contact of the weld onto all surfaces, plus then you could grind the flat surfaces smooth with peace of mind knowing you aren't going to be "thin" anywhere in the weld area.when tacking (ya, I know, your'e done that already) if you leave a slight gap between the flat boxing plate and the edge of the c channel frame you can watch as you weld to ensure the weld is right to the bottom of the gap and know you have full thickness contact.
6" welds may be a lot of heat concentration in a single area. maybe 3" would be better. it takes more time to be complete but the time spent weighed against the time spent to straighten a frame rail and lost time doing that when you could be doing something else, would seem like a deal in hindsight. just my thoughts though.

[whitedog76]

Well, I got them welded in. A little clean up and grinding, then we’re ready for the crossmember. I did bolt a piece of tube steel across the front also. I had previously notched the factory crossmember where the 235 motor mount was. Anyhow, I trimmed and cleaned it up. Anyhow, everything stayed nice and square.

Speaking of crossmembers... during a cooling cycle, I cut some plate and welded it in to take up the gap. Basically, I just boxed the backside of the crossmember upright.

Moving forward.