After removing the interior of my 914 I noticed that the floor of the car was painted the original metalic gold. The floor under the seats was not painted but were still black. The floor in front of the seats looks great with no rust anywhere, not even around the edges where it meets the frame sections. It is all sound and solid even from underneath. (under the car still has the original gold paint as well)
Under the seat was different. There is rust around the seat mounts and around most of the edges I was able to pry away enough black tar like stuff to see some surface rust. There was also some rust, not much at all, in the long depressions in the floor boards. It took me about two hours to totally remove the "black stuff" from under the seat because about 90%+ had a great bond to the original steel. (no rust at all except at the edges) After sandblasting the rust that was there I found it was all surface rust and all I have to do is prime and repaint.
2 Questions for the experienced -
1- Given what I have found, would it be worth tearing out the rest of the "black stuff" in the front 2/3 of the car floor?
2 - What is that "stuff" and can I replace it with something as good or better?
In the picture below, only the dark brown colour was rust, the light brown was the bonding left from the "black stuff"
Tx
Doug

I recently removed the tar from the floorboards on my 914 and found some rust, even though it seems to be well sealed the water can still get in. I stripped everything to bare metal and used POR-15 everywhere inside. i am planning on use ing some dynamat type sound deadening before installing new carpet.
Brian

Lucky you. Look at mine, er...... well whats left of it

Tear all that shit out, clean, POR 15, then jute (carpet padding). If you ever get wet, easier to fix. Dynamats good, but sticky.

Just to expand on bhfast's answer a bit. It's pretty common (around here at least) to remove the black tar paper because of the rust you're seeing. I have to wonder if there was a cost savings to painting the car after this stuff was installed or if this was an acceptable practice before cars were galvanized.

Anyway, it's a good idea to do what he did and remove it all. Put down a good layer of rust protection and then put something back on top of that if you want.

I've also considered drilling drain holes in the floor and trunks since almost all 914s leak water somewhere.

To remove the tar paper I've used a strong putty knife and either a propane torch or a heat gun. Both work equally well but propane is better at stinking up the garage.

Good luck.

Jon

Dude I swear our cars were separated at birth but went on to lead similar lives. I cut the exact same panel out of my Olympic Blue 914 over a year ago.

Jon

the black "tar" stuff is sound-dampening ...
it's usually rusted underneath after 25+ years. so
removing it is a good idea! use a heat-gun to warm it up, it'll
peel of in big chunks, much easier to remove :-)

get rid of all the tar mats, clean the metal, put on
"metal ready" than spray or brush over with por15.
this will seal it off against future moisture (which you will get for sure).

you can put in new tar mats on top of the por15.
without the tar, the car will be noticeabley louder, especially
at higher speeds.

later,
Andy

forgot the "mandatory" pictures

before:


after:


later,
Andy

jonwatts
Its like Deja Vu Whats your chasis number?

Sir andy DAMN Thats a thing of beauty!!

yeah, and it gives me head-aches too

j/k, i love my car!!!!!!!!!!!

Andy forgot to mention the added benefit of covering up interior paint that isn't the same color as the exterior

Korijo, my chassis number is 1077. If you're into numerology that means..... nothing.

Jon

Thought this might help.

I just went through the process of stripping my interior.

Two tools that made it easier.

1. blaster tool made by Wurth - has rotating metal prongs
that work much like a sand blaster without the mess.

2. an air powered chisel for removing black tar and seam sealer.

Bill

Havent tried it but it was suggested to use dry ice on the sound deadening material it supposedly hardened and cracks making easier to remove.
This was for 356's and I assume the material isnt much different (it doesnt look and different)
On my 356 I used a putty knife and a paint/rust grinding bit worked well but sure was time consuming
BTW my 57 356A was painted before the deadening material was installed.

-Kelly

Has anyone needed sound deadening on the firewall? Does undercoating or anything like that on the inside of the firewall help or is it even needed? I noticed one picture above "SirAndy"sprayed the firewall along with the floor. Was this just por15 or was there more?

There's a very heavy rubber piece that goes on the backside of the firewall to deaden the sound. That sucker weighs a LOT. Not sure how much louder it is without it, but I know a lot of people take it out.

yeah, the black stuff you see in the picture is por15. that's just to keep the moisture out. (AND cover the orange paint ) ...
i never had the rubber piece that goes into the engine compartment, but i've been in cars that do and i can say that it makes a big difference!
i won't be able to have the back-padding on the inside firewall anymore because of the roll-cage, so i've been thinking about getting a rubber mat for the engine-compartment.

as to the tar-mats, heating them up with a heat-gun works very well, you can then scrape it off in BIG chunks plus it doesn't leave much leftovers on the metal. once i had the tar mats out, i simply cleaned the metal with brake-cleaner. (gives you a buzz too )

later,
Andy

and if you don't have a heat gun, just use a plumbers torch. don't heat it too much, just enough to scrape it off with a putty knife in large hunks.

I haven't really looked yet but can you buy precut tar mats? When installing them, do you heat them up to bond and form to the parent metal?
I've never really seen them like this before so this is new to me.

Tweeks has tar mats now, though I don't plan to get any. I just tore out glued on, fiber sound-deadening material underneath the carpetting. It was like a sponge. This was a CA car until last spring. Any suggestions on the best chemicals or other techniques to get the remnants of the glue off of the floor?

try brake cleaner.

Hey Sir Andy, how'd you get 2 pictures in the same post?

Oh, wait. I see. They're on another server somewhere.

Nevermind...

Mike T

I had the fortune of pulling tar off without heat gun. . .. ~10 hours . . . and with heat gun at Brad's shop ~2 hours . . .

I like the heat gun version better.

-'Chung

Don't work smarter, work harder. . .