BenUK

As part of my body-off resto I've cleaned the paint and underseal from the bottom of the floor on my '76 and revealed lots of rust holes.









The "right" solution to me seems to be a complete replacement of the floor, including the transmission tunnel, in one piece. The floor seems to be bonded and rivetted at the front and back, but what about at the sides? Is it bonded or spot-welded? What's involved in the replacement?

I don't think I could patch up all the holes with body filler but if replacing the floor pan is too difficult (or if I can't find a complete replacement here in the UK) then this might be my only option.

Would love to hear some wise words from those who know.

78Vette-SA

If the tunnel has no holes or damage DUE NOT replace the tunnel. You can buy pans (about $259 each) and install them with some effort. By looking at your pics, they need to be replaced, not patched. You can just do the bad section and not the whole pan if the seating area is fine. But it might be better to do the works.

If you have any questions just let me know.

Here's a link to some info and pics:

http://forums.corvetteforum.com/c3-t...placement.html

BenUK

Thank you Joe. I searched the forums earlier but didn't find that thread. Doh!

In this photo you can see terminal rust in the side panel of the floorpan:



In your photos it looks as though you didn't replace any parts of this panel - your floor pans fitted to that original piece. Is that true?

I was hoping to avoid having big obvious seams visible under the car from a partially-replaced floorpan. What's the reason why you say I shouldn't consider replacing the complete floor, including the transmission tunnel?

78Vette-SA

That is all part of the pan and was replaced also. IN the one picture you can see the seam from the seam sealer. Everything below that was replaced.

noonie

You can see here some of the original construction. This floor was in pretty good shape with no holes. Cleaned it with a wire cup wheel, etched with OSPHO, primed with zinc chromate and finished with Rustolem.
You can see the spot welds o the outer sides.






In your case, assuming you don't have some of the equipment, and being over there, I would just clean it top and bottom to bare metal, clean and etch it with phosphoric acid, glass it from the top with epoxy/and 3/4oz mat. The bottom can be completely done the same way, then sanded, painted and sprayed with rust proofing/sound deadener. It will out live you it prepped right and be unnoticable.

I've done it both by welding and glassing and the welding is much, much harder to do, and time consuming so it is not noticeable.

chris75stingray

it looks like there is only one bad spot with that big hole in it. i don't think it's worth replacing. clean it down good on both sides to bare steel. i'd glass it like noonie said but only on top. put some tape on the underside were the holes are so the resin doesn't drip everywhere. build up enough glass on top so it's strong enough. then underneath i'd use some rust preventing paint like por15 and then undercoating .

markdtn

You can buy a complete floor from a later C3 and replace the whole thing. There are a few differences in the '78 up pans but overall they work out. You could also go to a power '78 up seat.

BenUK

Thank you all for your input.

I'm encouraged that a couple of you think that a glassed-in repair would be OK. I think this has been done before because through the holes in the steel I don't see the carpet; I see a solid barrier that I assume is fibreglass.

I really didn't want to get sucked in to redoing the interior during this body-off project. I could stand a new carpet but that's about as far as I want to go.

Perhaps I'll patch the floor with fibreglass and hope it survives a couple more decades. I'll replace the steel next time.

glen242

Ben:

I purchased a small, cheap Harbor Freight sheet metal bender, some 16? gauge sheet metal. Foot wells in my '76 had some small to medium size holes, tunnel and sides were ok.

Bent the metal to cover the foot wells and up both sides and overlaped into the seat mounting area. Preped the bottom side of the patches with rustoleum. Spot welded the patches and and then 'glassed in the interior side with cloth and resin.

Lacking a spot welder, I believe aluminum pop rivits could be used to hold the patch in place.

It has been 6-7 years since the repair, and no problems.

dariopop

Ben, I also have a 1976 and my floor pans were like yours. I ground out the rust and got it down to bare metal and I fiberglassed the whole inside of the floor pans on both sides. I did this more than 15 years ago and have not had any problems. Good luck!

BenUK

Thanks again for the extra info. My Dad has experience of patching bodywork with fibreglass and he thinks it can be repaired that way, although the worst area of rust on the side of the footwell may need a metal patch. I need to clean it up properly and take a closer look.