I have a 59 Impala that I'm going to install reproduction floor pans in this winter. Back in 1988 or so, we cut out the rusted area in the rear floor pans and front passenger area and just used sheet metal and fiberglass to patch it up - reproduction pans weren't available.

I've purchased pans from a classic car supplier in Arkansas and they'll be here next week. They assure me that these are made in Michigan and high quality.

My next move is to find a competent local welder who can install them. I'll cut out the old stuff and leave as much of the good, original metal as possible, with the hope of minimizing the time the welder needs to prep and weld.

My question to the group is:

Is overlap welding OK? One welder I spoke to today said he'd use this method and then some high quality seam sealer to seal the overlap areas.

Is seam welding better, but requires more time and precision?

I'm accepting the fact that I'm going to have to pay for quality, "done right" welding vs. lowest cost.

Any tips or questions to ask the shops/welders that I talk to?

Thanks
Russ

Do you mean skip welding?


Regional weld slang varies, but in my circles an overlap weld is a lack of fusion weld defect usually caused by holding the electrode at the wrong angle or too large of a welding wire.

quote:

Originally posted by Russ59:
Any tips or questions to ask the shops/welders that I talk to?

Thanks
Russ

Ask welding process they're going to use. Tig would be a cooler welding process less likely to warp the thin sheet metal floor pan. A hotter process like mig or stick requires the skip welding to move to different regions or the thin gauge metal will warp. A skilled welder can successfully do the job with any of the three, but many would choose tig.

I grew up with a Dad in autobody, and have watched pros weld in floor pans and door skins in my personal car and Dad's personal car. I'm also an oil & gas engineer who likes to geek out with welding engineers.

Using a panel flanger for the overlap would be the strongest. But either method done correctly would work, the welder may be more comfortable with one over the other.

Tator, with overlap, I was referring to the two metals overlapping a bit and then spot welding, followed by seam sealer I believe.

Overland Restoration or Jerry's?

Lap joints vs butt joints.

Cutting it out so you don't have to overlap is going to take ages longer for sure. IIRC there's a tool to make a recessed lip for the new pieces to sit in, so at least from one side it doesn't look like a lap joint.

I know you’re having someone else weld this, but you can do a lot of this to prep it for the welder and keep the labor down.


Take a piece of chipboard (hard non corrugated cardboard) and lay it on a table. Flip pan onto chipboard. Trace pan shape with sharpie. Cut chipboard to match shape of pan. Test fit to pan and adjust/cut chipboard to make PERFECT match. Transfer chipboard to car and secure in place (I used sheet metal screws). Scribe your line onto the car floor. Take your time and precisely cut floor to scribe line.

Test fit pan, it should fit nicely. You may have to use a hammer to persuade the fitment it it’s not a perfect match. In this sense I mean shape of contours. It should fit cleanly in the hole. We are not trying to do square peg/round hole with the hammer.
Use a flappy disc to clean the floor metal very well.

If you have a TIG welder available, use that as it will be a much cleaner, and cooler weld.

On the underside of the car at the four corners of the pan, you can tack some rod across the corners to act as holders for the pan, as the pan should be tight, but able to fall through the floor and into the ground. This will hold it in place and the holders can be easily removed after the pans are in place.

Tack pan in place. Follow Todd’s example of skip welding. Take lots of time doing this. You’ll want to weld an inch and move to the opposite side alternating the heat in a pattern similar to tightening lugs on a wheel. Take lots of breaks to let the metal cool to prevent warpage, but you’re also using heat to control warpage, so after an inch on all four sides, give it a few and repeat process.

Thanks Bean for the advice. I do plan on prepping the surfaces as much as possible. Once I find a welder, I'll confer with them on how much to cut off and what other prep they want me to do.

I do like your suggestions for mocking up the old and new pans.

In other news, the pans arrive today - two days early via UPS.