> If anyone is considering the ghastly job of stripping the underside of there
> Pantera back to bare metal and repainting it. I would be happy to start a new
> thread and tell you best methods, and the correct paints to use.
Too late for me to do anything about it now but I'm interested in hearing your
thoughts. I just went through the nasty task of stripping the undercoating
off my Pantera. Some pictures of the work-in-progress are at:
http://www.bacomatic.org/gallery/album03
The pictures aren't best but I was in hurry. I'll try to take some better
pictures of the results at a later date. I wasn't really planning on
stripping the original undercoating off but I had recently welded-in a set
of dropped floor pans to gain some much needed headroom and my buddy at
the body shop suggested I paint and undercoat the new pans after stripping
off the old undercoating. Easier said than done! He said the old
undercoating was a tar-like substance that dried out over time and might be
concealing hidden rust. We debated putting on new undercoating for a bit
before deciding to do it. According to my friend, the new 3M undercoating
doesn't dry out and does a better job of protecting against rust.
As it turns out the old undercoating didn't want to come off. The only place
where it was easy to remove was near the mufflers. Everyplace else it was
holding tight. I used several different die grinders (Dotco, ARO, and
Ingersol Rand) that spin in the 20K to 30K RPM range, fitted with industrial
quality twisted wire brush wheels. I tried a few cheaper wire brushes from
hardware and auto body supply stores but the industrial die grinders (supplied
with 160 PSI air) just spun them apart. Slower die grinders wouldn't remove
the stuff. I also used an air chisel (along with a hammer and chisel). The
air chisel fitted with a blunt tip really stripped the heavy stuff off but
it can nick the metal so don't use it on panels where the other side shows
(like the rear inner fenders).
I spent a couple of days on the bottom of the car and a couple of days on the
fender wells. After each session I'd come out looking like a coal miner with
the stuff stuck to my face and in my hair. Probably would have been smart to
where a mask but... Anyway, I was really happy to see my car had virtually
no rust. There were only a few places that had any rust: the places that had
not been painted or undercoated from the factory (underside of an upper frame
rail), underneath one of the rubber pads the gas tank sat on, and around the
rear fender lip. The fender lip rust was hidden under a light layer of
undercoating and had gotten a little grainy. The other places were superficial
surface rust that scubbed off using a 3M Scotchbrite pad soaked in phoshporic
acid but I took a 90 degree die griner with a 3M Scocthbrite disc to the
perimeter of the fender lips. Turn the speed down on the disc as it will
eat metal if you're not careful. I left the factory undercoating on the inside
upper surface of the fenders since it would protect better from stone chips.
After all the undercoating was off, I wiped the car down with 3M pads soaked
in phoshporic acid (in the form of PPG DX-533 aluminum cleaner). The phosporic
acid will eat the rust out of pores that sanding and wire brushing may miss.
I had planned on using POR-15 to paint the bottom of the car. I'd recently
been given a 10' by 3' steel work table. It's a really nice two level piece
with twin drain basins but had been sitting outside for a few months and
was showing some surface rust. Anyway, I stripped it to bare metal and shot
it with silver POR-15 and it turned out great so I thought I'd give it a shot
on the Pantera. However, a friend who works at a body shop suggested SEM
Sheild. He'd tried POR-15 with mixed results and liked the SEM Shield better.
SEM Shield is a rust inhibitor paint available from auto body supply stores
and comes in a wide variety of colors. We sprayed it from a paint gun but
also used aerosol cans and a brush in areas where we couldn't get the HVLP
gun into. Once the paint was sufficiently dry, we topped it off with a
layer of 3M undercoating.
We also repaired a dent on the door (I tripped and dropped a cast iron
cylinder head into the door, Doh!) and repainted all the black parts of the
car. In prepping the rocker panels, we noticed a few little bumps starting
and decided to cut a spot out to see if it was rust. It was. The rest of
the rockers were solid but right at the spot below the forward edge of the
door, there was a piece of seam sealer inside the rocker panel that formed
a dam that kept water from draining out, causing the rust to start. We did
both sides with small patch panels after giving the interior of the rockers
the wire brush and DX-533 treatment. After the panels was repaired, we were
able to blow in some SEM Shield and rubber undercoating. One downside to
the new undercoating is that stays wet and will rub off easily. Luckily,
it's available in aerosol cans and easily touched up.
The gas tank was rust-free inside and out except at the very top of the
tank where fuel rarely is. What's there is very light surface rust but
I still need to get in there and remove it before I re-install the tank.
While we were at it, we welded in pick-up points for the 4 piece chassis
reinforcement kit and relocated the pressure tank. It seems like anything
that would come off the car was stripped to bare metal, primed, sprayed
with 2 color coats and a third coat of clear. I've got an entire room
covered with freshly painted parts (pulleys, coolant tubes, radiator bits,
brackets, pressure and overflow tanks, etc.) off the Pantera. The coolant
tubes and radiator tanks turned out to be in great shape. I was planning
on replacing them with stainless parts but I may reconsider.
Inside the frame rails I can see some surface rust. I was planning on
trying to flush it with a rust converter (like SEM's Rust Mort). I'm also
going to look into the cavity wax that Johnny Woods mentioned (very timely
post for me, thanks!). Still need to polish the aluminum gas tank cover
but I've started stripping the front trunk, after welding in a flush mount
stainless steel battery box. Also need to paint the interior floor pans
after all the welding and I've purchased a bunch of B-Quiet acoustic materal
(like Dynamat but less expensive) that I need to install before putting the
interior back in.
Anyway, enough rambling.
Dan Jones
St. Louis, Missouri
1974 Pantera L
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