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I think I remember reading several posts in the past regarding drainage holes in the floor pans. Are some holes supposed to be there? If so, how do I know which are intended to be drainage holes and which do I need to close up? Also, do the drainage holes get rubber plugs installed or do they just remain open? (I have seen some plugs in the catalogs, and I am not certain where they go.)

Is there an easy reference to use, such as the shop manual or something?

I am getting ready to POR-15 the floor, and I don't want to plug up any holes that are supposed to remain open. Thanks.
 

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The drainage holes are oval holes about 3" X 1.5". They are sealed with an oval metal plug that is either screwed in or glued in using seam sealer. These plugs are available from any Mustang parts supplier. IIRC their original purpose was to drain the unit body after dipping.

You can just seal them up, as they serve no useful purpose on a leak free car.
 

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A completed floorpan should have no openings to the outside. The four holes under each seat are to access the seat bolts and should have rubber plugs in them. The factory drain holes should have the metal plugs sealed in place. Any other "drainage" hole will only allow water to enter the car, soak into the carpet and underlayment, and rust out the floor.
 

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IIRC their original purpose was to drain the unit body after dipping.
You know, I never considered the purpose for all those drain plugs until I read this month's MM when they toured the DAP. Now that I think about it, they make a lot of sense to drain out the chemicals from the pans, frame rails, quarter panels, etc. When you think about the unibodies traveling through the dip tank they would need some way to get rid of all the excess that would otherwise be trapped in there. I learned something today! Woo hoo!
 

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Did the acid etch leave any rust prohibitive properties to areas that weren't painted, such as inside the rockers or frame rails?
 

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Did the acid etch leave any rust prohibitive properties to areas that weren't painted, such as inside the rockers or frame rails?
I severely doubt it. Acid etch only removes rust and oil impurities to help prep the metal for paint.

BTW, this is the best explanation for why the drain holes are there (acid etching prior to painting), but I've not seen confirmation that Ford actually dipped the chassis prior to painting. I'm not saying that they didn't, but it would be nice to confirm that with someone who worked the assembly line at the time.
 
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