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would this make a rusty pair of exhaust manifolds look new or just all scratched up?
 

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it would turn them a kind of a shiny silver gray... not like new cast iron.. but very clean.. It will look better than the rust!....
 

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Hi Evans71,

I think the resulting finish depends on the type of sand/media used. I've used regular silica sand on several manifolds and ended up with a dull gray finish. Something a bit smoother (like bead blasting) would probably give a somewhat shiny silver gray finish like veno described.

In any case, freshly blasted cast iron won't stay clean and new looking for long. You'll need to apply some high temp paint or other protective coating so they don't get all rusty again.
 

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I have glass bead blasted intakes before and clear coated them, came out nice, a grey color, not like raw aluminum.

For an exhaust (steel or cast iron??) if you blast it its gonna rust quicker than yesterday. The high temp BBQ flat black paint may hold up to the high heat for awhile. JR
 

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You can blast them and then powder coat them in HIGH temp gray. I have done a few for some customers and they hold up very well. The powder temp I think is 1400 deg..
 

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exhaust blast...

I have had the best luck doing the following: media blast with medium abrasive...clean with solvent and blow dry . Then shot peen them at a machine shop....this is small metal shot that is used on engine blocks and heads. It smooths out the finish and removes the rougness from the sand blast and cast iron. Clean again....prime with high temp 1200* grey primer....finish with POR 15 gray high heat manifold paint. It is also a good idea to check the stud holes and run a tap thru them to clean up the threads....then install some new exhaust manifold studs and you are ready to go. You can also re-finish the heat riser the same way unless you are installing a new one.

wilma
 
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