Advice on replacing front Pan

Jim Smolka · 01-20-2002, 10:03 PM

Any advice or suggestions on replacing the front pan on a '74 911?

I have mig welder and a spot weld removal drilling bit

Thanks

bjola · 01-21-2002, 01:45 AM

Hi Jim,

I would say that this is normally beyond the scope of the home mechanic and would require some sort of rig to get everything lined up prior to welding.
If you get things out of line you end up with a car that is a bad driver.
You could probably talk to a repairshop and make a deal that you take the old pan out and they put the one new in?

Jim Smolka · 01-21-2002, 03:32 AM

I am just replacing part of the front pan, where the front part of the torsion bars connect to the car.

bjola · 01-21-2002, 05:17 AM

Hi again Jim,

Still.

When you cut out the foremost front suspension pick up points you have to very carefully line up the new pan before welding it in.
There are three areas you have to take great care with:

1, the distance between forward and rear pick up points for front suspention.
2, to level the forward pickup points vertically with rest of body (looking from the side of the body)
3, to level the two forward pickup points horizontally with rest of body (looking from the front of body)
4, to line up the pan so the pickup points are centered with the body centerline (looking from above).

If you have a set of workshop manuals you can get all the required dimensions from the body section (tolerances are tight!).

I do not know your previous experience with this sort of repair but I would say that it is a gamble without a fixture.

Brad_H · 01-21-2002, 05:53 AM

Jim,
There are several people on this board who have successfully done this at home. I'm in the middle of the job myself, if fact, I'm about to go out and weld right now. You should use the search button to read the old threads.
A good book for this job is the Haynes Porsche 911 Restoration Manual. It has some measurements listed. You install the new pan with the A-arms attached, so you can't really mess up the front-to-back position. I was told by one guy that he didn't take ANY measurements, because the new pan only fits in one way - exactly where the old one was. That's kind of true, but I found that you can fudge it up and down a few mm. I took all kinds of pre-cutting measurements, and found the up-down pre-measurement the most useful.
It's a big job, but I haven't read any do-it-yourselfer horror stories of ruined cars because of misaligned cars. Also, the shops I talked to didn't use a frame jig either.

john walker's workshop · 01-21-2002, 08:10 AM

i've done lots of them, and once the seam around the front and sides is split and smoothed, it pretty much self aligns. clamp it along the seam with visegrips and then make the cut on the sides of the gas tank hole. one caution though. some repair panels do not have decent welds on the suspension mounting area and they will seperate down the road. there's only 2 or 3 spot welds on some. total crap. so make sure yours is a good product before welding it in.

BK911 · BK911's Garage

Any advice on how to split the seam around the front and sides? Dremmel? Plasma cutter? Chisel?

Thanks!
BK

john walker's workshop · 01-21-2002, 08:52 AM

the spot weld cutter bit makes a large hole, so i don't use them much. i would cut along the inner edge of the seam to remove the majority of the pan, leaving the lip, and then do some grinding with a small makita disc grinder. the seam can then be seperated between the spot welds with a hammer and skinny chisel or screwdriver, causing some of the spotwelds to let go. some welds can be carefully chiseled open, some need to be ground down. the idea is to save the outer half of the spotwelded seam/lip. straighten it with a hammer and dolly, then fit the new panel.