How am I Polishing Wrong?

So I'm trying to polish my nasty old SLP LM1 catback. It is spec'd as being made from stainless steel 304.

So far I have practiced on one piece. I wetsanded with 600, 800, 1000, 2000 and 3000 grit sand papers. There are spots that look polished but the majority of it are cloudy. The cloudiness doesn't wipe clean. I tried starting over with 600-3000 grit sandpapers and it just isn't getting any shinier.

What am I doing wrong? Do I need to start with a lower grit? Harder? Longer? Or will this stainless steel not get much better?

Man, looks like aluminum on my phone. I started with 40 on the bends, then worked up. 600 isn’t enough IMO to start with.

Start with 220 minimum. Unless they were already in good shape.

Ahhh, you need to start with a lower grit to get it smooth. Even try with a DA first. Then go up in grits. After 2000 or 2500, you need a metal polish compound, not just sand paper. Key is to sand with the grain of the metal.

I use a bench top polishing wheel and mothers metal polish for a mirror finish on mine.

You're starting with a used catback so it's going to be quite a bit more work than a brand new system. I'd start with 120-150 grit and see how that does. You need the entire surface of the pipe to have a smooth consistent appearance(no scratches, cloudy areas, rust, etc) before moving up to the next grit.

I'd also recommend using a power sander like a 5" random orbital or even a palm sander. I put about 12 hours into polishing my new catback using power tools. A used system polished by hand would probably be 20+ hours!

you polishing guys are nuts, dont they make chrome header paint even?

In my experience, you should be able to get a shiny polished appearance out of it once you actually polish it, even if you still have scratches from your sanding. Sanding will just give you a good base for the polishing process.

Take it to a metal shop. Save yourself 20 hours. I think mine was $150 and it’s like a mirror

Start with a much lower grit paper. Then sand until all the scratches are gone from the previous grit.
Work your way up through the grits.
Any imperfections in the pipe will be seen, so don't go to the next grit until the pipe is smooth and free of imperfections.

Here ya go! I think this video will help you a lot. He started with 400 grit (with good results), but you can start with 180-220 grit, as others recommended. He does occasionally sand against the grain, but again, the result he got was great. You can choose to stay with the grain 90-100% of the time. Overall, the video gives you clear instructions on polishing your catback.

My current exhaust wasnt in as good of shape as my first cobra. I had to start with an 80 grit sand paper flap wheel and went up from there. You cannot just jump right into the wet sanding. You need to get under all the old crap first. Also if you want it perfect take your time. I got 10-15 hours in mine and they could have used a lot more time.

DSG2003Mach1 said:

you polishing guys are nuts, dont they make chrome header paint even?

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I rather drop it off and get it chromed or even ceramic coated black over spending the time to polish it.


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Here's a great thread that @04sleeper started back in 2009. It's old, but well worth reviewing how he did his. Lots of instructions and photos. Great thread!
https://www.svtperformance.com/threads/how-to-polish-your-exhaust.568983/

Once it's polished, they are easy to maintain (unless someone's DD'n one of these cars).

What's deteriorated on mine over time is not the polished pipes....they look great! It's actually the borla chromed tips that look like crap. I've actually thought about pulling the back section off, strip the chrome and try to polish it out mirror. I'd rather deal with that than look at this crappy chrome

c6zhombre said:

It's actually the borla chromed tips that look like crap

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my MRT chrome tips are getting rough but not bad enough to deal with yet

Best of luck to you sir. May your fingers stay sore for many weeks to come.

3" Bassani for reference

c6zhombre said:

Once it's polished, they are easy to maintain (unless someone's DD'n one of these cars).

What's deteriorated on mine over time is not the polished pipes....they look great! It's actually the borla chromed tips that look like crap. I've actually thought about pulling the back section off, strip the chrome and try to polish it out mirror. I'd rather deal with that than look at this crappy chrome

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You can do that. Mine were looking rough so a shop stripped them and we were both surprised to see the stainless under there. Now it's just a matter of keeping up on them like the rest.

1Kona_Venom said:

Best of luck to you sir. May your fingers stay sore for many weeks to come.

3" Bassani for reference

View attachment 1623501

View attachment 1623505

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Those are one the nicest polished pipes I've seen here. Nice work! Your got some really sore fingers in the end, but the result was worth it. Yes?

^ I started with an SLP Loud Mouth 1 and it wasn't good quality, like the OP is describing.
I ordered a new 3" Bassani catback and immediately took notice that the metal and composition was much easier to work with.

I also employed "machine techniques" throughout, which saved my fingers

@NateDogg purchased that catback from me years later and it was virtually maintenance free.

1Kona_Venom said:

^ I started with an SLP Loud Mouth 1 and it wasn't good quality, like the OP is describing.
I ordered a new 3" Bassani catback and immediately took notice that the metal and composition was much easier to work with.

I also employed "machine techniques" throughout, which saved my fingers

@NateDogg purchased that catback from me years later and it was virtually maintenance free.

Click to expand...

A polished 3" Bassani is the only catback I'll run now because of the one you did!

I have a brand new one waiting to be polished for the new car!

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