70 Under Body Finish

[Mike Farman]

Hello all:

First, I've searched all the archives for combinations of under body finish, and come up with nothing...

I have a '70 Convertible, and the entire underside had been thickly coated in aftermarket undercoating. I cleaned much of it away, then had the body media blasted to clean it. Now it's bare fiberglass. I understand that it shouldn't be painted, other than a bit of overspray maybe at the edges.

I have two questions. First, what should I do about all the underbody steel brackets, rocker areas, etc. I don't want them to rust, so they need some sort of coating - should they be blacked out, cleared, or something else? Secondly, I'm concerned about the fiberglass as although it looks new, the surface fibers are exposed, and would wick water while driving. Can I clear the underside, perhaps with flattener in the clear to seal it and replicate the appearance of resin?

[Wayne P.]

Re: 70 Under Body Finish

Most metal under body brackets should be black. A mat/satin finish clear would help protect the glass and maybe not hurt judging(hard to detect).

[Mike Farman]

Re: 70 Under Body Finish

Thanks, Wayne. Were the steel brackets (under the seats for example) painted before installation, which would indicate careful masking at this stage, or were they "blacked out" during assembly, in which case there would be overspray around them? How about the rivets that hold them on? Similarly, how about the steel in the underside of the sill areas? Rgds, Mike.

[Terry M.]

Re: 70 Under Body Finish

The painted steel underbody brackets (under the seats, for example) were coated before installation on the car. Thus the rivets will NOT have paint on them, nor will there be any overspray from the coating of this bracketry. Not all underbody bracketry was painted, and none was coated after installation on the car. I suggest you rely on the study of low mileage original cars for which were painted, which natural, and which might be otherwise coated. There are posters here with such cars who can help you on specific bracket by bracket questions. Shotgun questions will be harder to deal with, and likely will receive fewer responses. If your goal is factory original results, I suspect in the long haul you will come to regret the "torched earth" results of underbody abrasive blasting.

By the "steel in the underside of the sill area" I think you are referring to the birdcage material. If so, that was coated with zinc chromate, but I don't know if that remained the typical olive drab green on the underside of the car. Others will have to expound on that.

[Patrick H.]

Re: 70 Under Body Finish

Agree. I think that I would have recommended taping off all metal parts to protect the finish prior to media blasting. In addition, as he has noted, now the fiberglass is rough. I would suggest (too lately it appears) that there are other less destructive ways to remove undercoating.

It is possible to now restore each bracket to correct appearance, but it will take work. That will include examination of other untouched cars to take notes and see how it should appear. Some people also use a semi-flat clear to "paint" the bottom of the car and seal it at this point.

Patrick