Sandblasting exhaust

[dbrody]

I'm working on removing the surface rust on the exhaust system ('69 vintage). I was going to sandblast the whole thing (out of the car) and paint it with a high temp paint. I also have all the sheetmetal from inside the engine and heat exchangers that I was going to do as well. Any problems with doing this?

Dave

[Rot 911]

Should work ok. Only thing I would do is make sure you cover the openings to the heat exchangers or you might find the inside of your car filled with dust the first time you turn the heat on!

[pwd72s]

The heat exchanger outer metal is not all that thick. I had the same idea back in the late '70's...before anybody heard of SSI's...I got to buy a new set of factory heat exchangers after the sandblasting filled my originals full of holes ranging in size from pinholes to pencil eraser. Just my experience, may not happen to you.

[GIBSON]

I've had the same experience sandblasting old heat exchangers, except in my case the holes were already there, the sandblasting just uncovered them. It is thin metal, just try to weld it sometime.
I have a local machine shop that hot-tanks mine, then I finish them with a careful sandblasting. Once they have been hot-tanked, not much blasting is necessary. It's amazing how much oil those things can hold.
I've been spraying them with high-temp spray paint, I think the number is SP 104 or a flat gray. Anybody come up with a closer paint match?

Bruce Herrmann

[911pcars]

I had my original heat exchangers sandblasted, then powder coated during my decade-long rebuild. I've had them on for about 4 years. So far, no lifting, no flaking. Paint is still sound @ a measured 400ºF at idle. If I were to do it again, I'd ceramic coat them (e.g. Jet Hot or equivalent). These coatings protect both outside and inside metal surfaces from corrosion; reduces radiated temp. of exhaust system too.

Sherwood Lee
http://members.rennlist.org/911pcars

[tbitz]

I recently did this. I could not afford new SSI's so I found some used pre-1975 exchangers in good condition on ebay. I build a sand blasting box from 2x4 lumber and plastic sheets used for for vapor barrier. I bought a sandblasting gun and away I went. I first removed all the grease and oil using some de-greasing agent. Once they were clean and dry I started the sandblasting. It took a few hours to do each exchanger. I could only blast for about 45seconds and then wait a couple of minutes for my compressor to build up pressure again. I then painted them with high temp exhaust manifold paint (1200F). I put them on my car just a few months ago, and they seem to hold up to the heat well. Here is a before and after shot.

[T Bird]

Dave
I've done this a few times now (2 mufflers and one set of heat exchangers). As long as it's just surface rust, you will be okay. As for paint, Stoddard sells a high temp flat grey paint that duplicates the OEM color. To do this job correctly, the paint from Stoddard needs to be cured at about 400 degrees. I take my sand blasted and painted parts to a local metal refinisher who bakes them in his oven at 400 degrees for 30 minutes. My current muffler looks perfect after 10 years of use.

Curing the paint by running the car until the part gets hot is not a good solution, since mufflers and heat exchangers tend to develop hot spots.

Good luck.
John

[Jim T]

I did the exact same thing as T-Bird, except I didn't have them baked. Had them, and the muffler, sandblasted, then I used the Stoddard factory grey paint, which I shot out of a gun.

Stoddard says to start the car, and when the parts start to smoke, shut it off. I agree, its not the best way to cure the parts, because they will heat unevenly. But I just did that a few times, letting it cool completely in between runs, increasing the amount of running time each time, until eventually the whole system was hot. It worked well, and after 5 years the parts still look amazingly great.

[tbitz]

After I painted mine I baked them in my barbeque. Probably not the best way, but better than nothing?