911 Media blasting? Wire harness?

[tcsracing1]

First time stripping a 911.

What is the recommended media blasting material and practice?
remove Undercoat from under fenders, floors and engine bay?
Remove all cables?

What is the deal with the wire harness? Keep it in the car and wrap it secure or try to remove it for blasting the body?

Trying not to remove too much or too little... Suggestions appreicated

[John912]

You’ll get a variety of answers here. I guess it all depends on condition of existing undercoating and level of finish you’re attempting to achieve. I’m on my third full resto of an early 911 (bare metal, suspension out) and have been fortunate to start with original floor, very minimal rust cars where original undercoating was pretty much in tact. I plastic bag and tape harness ends, and use a liquid degreaser and pressure washer to thoroughly clean all previously undercoated areas, let dry and feather-in any areas that need patching. I restore these cars as a “hobby,” taking about three years per car working at a leisurely pace. The idea of scraping undercoating from a shell would take the fun out of it for me. Even “labor of love” has its limits! Solid media blasting (sand, glass, walnut shells, etc.) also is not appealing. I read/see advertised liquid blasting methods that look too good to be true – I would consider that route if it really worked that effortlessly. From what I see, your undercoating doesn't look that bad.

[76911S]

I would remove everything. It is the best time to do a complete inspection, repair, clean & replace of all of the hard to deal with later items. Having a bare tub is the best time to remove / install a complete harness. Chances are you will find some brittle wires that need replaced, or a whole harness that has been hacked. Cables and hard lines are fairly easy to replace, again now is the time.

I have used soda, but not super happy with that, leaves a residue that MUST be cleaned (not just hosed off) properly. Sand can be to harsh and damage panels if not done properly and leaves residue in all the nooks. I might try aqua blasting on a upcoming project, or just strip by hand.

Yes, I would remove undercoat, sound deadening, everything. You would be amazed at what hides under that stuff,,,, rust.

Yes, it seems overwhelming, but if your going to do it, do it correct and do it once, or it will need redone later.

Mark..

[smedley]

Looks like you're working on a '69...which means you're dealing with the first year of the "plastic" undercoating. This stuff does NOT respond very well to media blasting. Attempts to blast it off will result in over heated metal and warping. Softening it with a butane or MAPP torch and scraping has been the tried and true method...admittedly tedious, but works. The thin residual stuff left after scraping will blast off.

Pulling a harness is a bad enough job, and with old brittle wires can be more traumatic to the harness than bagging it in place. If it looks decent, bag. Only 100% peace of mind thing is to remove and replace...tedious and expensive.

Some may recommend chemical dip......if done correctly, OK, but I've heard too many horror stories of residual chemical that was not neutralized and captured in the pinch welds. This stuff can finally decide to seep out and ruin a finished paint job! $$$$$$ Any media will leave dry residual, but it's more of a nuisance than a potential disaster from residual chemical. I'm still vacuuming media out of the front storage area of my '67 S months later. Good luck and patience!

[mshaver51]

I've undertaken two restoration projects, and my experience overlaps with the other suggestions (above). You have two separate questions: first regarding the steel, and second regarding the harness. As far as the harness, I have chosen to bag/wrap it and leave it in place. In a restoration, the idea of "new" is hard to resist, but dragging a harness out of a carcass is no picnic, and to me, getting the new one in the right places is a pain unto itself. Of course, there will be brittle wires and bad connections in a 50-year old harness. There might also be weak connections in a new harness, or you might drag a wire against a sharp edge and create a short. It's a tough call that is mostly validated by hindsight. Good luck.

Regarding the steel, you have a genuinely complicated decision to make. As John Schiavonne suggested, if you are happy with the condition of the steel, the idea of a detergent power wash will allow the grease/grime to be removed. If the steel is solid and rust is absent, I would be happy with that. This alternative is certainly the least work. The problem for me is that (being in the midwest) I can't imagine a rust-free tub. The power wash might blow the undercoating off of areas of rust ... or not. The worst situation would be having rust ruin a new paint job.

I have always assumed that rust was in there somewhere (again, the midwest). As others suggested, when I used media blasting, honestly, 20 years later, I am still finding residue. I also have a friend who had a carcass dipped and the stuff was oozing out of weird places for several years. For my most recent project, I mechanically removed the undercoating to expose bare steel. In some cases, I used power wire brushes. I looked like a coal miner and my garage was covered in a layer of soot. In other areas, I used a propane torch and scraper, which was actually much cleaner. Neither alternative was pretty. Outdoors is the best venue, if possible. So, if you choose this alternative, make sure you urinate before you go into the garage (because your wife will kill you for tracking that crap inside) and get used to getting naked in the garage and possibly being forced to burn the clothing you just removed.

But when the steel was all exposed, I knew exactly what was needed for everything, and knew which repairs I could make and which ones required professional help.

A side issue which you did not mention seems also worth mentioning. Stripping an old car is hard, filthy work and it takes a long time. During that time your frustration (as I was) might tempt you to think it is simpler and cheaper to bundle it up and take it to a shop. If you take it to a shop before you have it completely stripped, be prepared to receive a phone call every two weeks and hear, "we found more rust," which roughly translates to "add another 10% to the estimate." Having to clean the carcass to bare steel means that you have the most intimate knowledge of your car, and it provides solid protection against getting overcharged. However, some guys don't want to get that intimate. (It's like meeting a really cool lady and finding out that she has irritable bowel disease ... you want to know everything about her, except that.)

Regardless, good luck, friend. You will find that the Early S Registry has lots of advice as you go along. Some of the advice will be like mine. Some of it will actually be useful.

[76911S]

Interesting comments above on leaving the wiring harness in place. For some of the stated reasons alone I would remove it . Almost 50 year old wires still in place, old brittle, think shorts and fires. It really is not that hard to remove and reinstall, a pain yes, but not hard. A new harness would be pretty easy.

I have to say, if the undercoating, wiring etc is not removed and replaced / refurbished it is not a restored car, just a cleaned up and repainted car, but that is a whole other topic on it's own that I am sure has been discussed to death.

Mark..

[tcsracing1]

what kind of media are folks using nowaday?

[mshaver51]

i am interested in the media question, too. i was leaning toward soda for my next project, but '76911S' has educated me on the potential pitfalls there. sand or coal fines are too aggressive for my taste, and i am not terribly interested in the large volume of plastic debris from plastic media. it seems like the process of education/elimination is leading back to some form of mechanical removal to expose weak metal. mechanical tools don't tend to get into the tight places too well, so maybe it will be necessary to blast those small areas.

on the other hand, we might have unwittingly hijacked this thread a bit, even though we are still discussing the original topic. if so, my apologies.

[tcsracing1]

We typically use black beauty on rusty american muscle cars. But i think it is too course for the 911.

Dustless water produces too much mud for my taste. It can get trapped in tight corners etc. Dirty.

I am consulting with a company that offers walnut, glass, plastic etc.... to see what is best. No warping etc.

We want an almost "white" finish as the end result before we take the wire wheel to it.

I am doing two 1969 tubs.

[mshaver51]

69s have a bad reputation for rust, especially here in the Midwest. good luck, but i agree with your conclusion on the black beauty. it can really rip holes in weak steel, and the rough surface it leaves behind almost seems to absorb water from the air. also, it doesn't work very well on either the undercoating, or any bondo, so if you used black beauty, you still have to deal with those obstacles. for undercoating, i tried several methods of removal and a propane torch with a scraper was the best, except for the mess left behind. the best method i found for removing bondo was pure mechanical grinding or power wire brushing.

i never considered water/mud. it seems too much like the cause of the problem to be a trusted solution.

to the extent that it matters, i have historic preservation clients (buildings, statutes, etc.) who demand using walnut shells because it is so non-aggressive (again, the key is PRESERVATION with them). it will knock the oxidation off of bronze and copper, but you might be there a long time on rust.

i've used glass beads on parts, but never on anything as large as a carcass/tub. there seem to be several plastic media types, depending upon desired aggression. neither of these seemed to cause much heat.

please share what you decide, and what you find from the experience. it will be good knowledge for the community.