I picked this car up a few weeks ago knowing that the floor had rust, didn't know how much until ripping up the carpet. My dumb question is this a prime example for pan replacement? The drivers side has no holes. I was hoping I wouldn't have to replace the floor, maybe just sand and patch the weak areas. This is going to be my "Driver", in good weather. I do need to track down the cause. Thanks.

 

yes you can sand the floor and use a rust encapsulater on it like por-15

the usual cause for bad floors is leaking windshield or rusted window channel

If you get a flashlight and look up under the dash you can see the bottom of the front window channel and might give you a better idea if it rusted or not

 

The 66-67 Cutlasses are famous for rusty windshield and rear window channel rust, pull the windshield to find and fix the holes. If your floor pans only have the holes shown, they can be patched by welding in new metal, but, if there are a bunch of pinholes, you will need to replace the panel to fix it right.

 

pinholes are easy!!! Its noting 300-400 tac welds won't fix

 

Looking at the pics you are going to need to replace about a 2x2 foot section of floor. You have to have clean solid metal to weld to or you will be pulling your hair out.

As others said the source is more than likely the bottom of the windshield.

 

Depends on how thin the rest is. As Richard said about the welding. You need clean SOLID material.
Something that small I would clean/treat the rust and use Rust Encapsulator or Por-15.
I would guess the trunk pans are similar.
Do you want a little work or A LOT?

 

Thanks for all the replies. The windshield and rear window are definitely leaking. The underside of the floor pan had been undercoated so it looked fine at first. Probably will replace the pan where needed. Thanks again for the input.

Dan