just bought new 2017 red corvette red 7 speed love it. but i noticed when i opened the hood the exhaust manifolds are all rusty. is that because the car sat out side at the dealership a long time or what. they should put some kind of coated exhaust manifolds for what you pay for the car. is that because they hold heat better stonger dont know.

 

Hmm...good question. When I put in my Headers, they were nice and shiny still look pretty good today!


Congrats on your new Vette!! Nice to see the 7 speed....

 

Exhaust manifold, other than Z06, is cast iron. Cast iron rusts like every other car! If you haven't looked, the stainless steel mufflers where the exhaust pipes are welded on the end is also rusted.

It is 409 Stainless many use for pipes and mufflers but it has the minimum chrome to make it stainless and no nickel like 304. However it has a very thin layer of aluminum that keeps it shinny (called aluminized, you can google if you wish.) But where there is a weld bead and the weld Heat Affected Zone (HAZ) as well as the weld spatter, no aluminum coating, hence rust. The HAZ gets hot enough when welding to burn off the aluminum.

I used a product called Rust Reformer (<$10 at Walmart) that turns rust blue black. Easy to use but tried it on the exhaust manifolds and did not work as well.

Now you will have you bend down and look there and being even more concerned!

You could buy 304 stainless headers ( and void warranty as that requires a tune!) You could also buy 304 Stainless Steel mufflers and pipes from folks like Borla, like I have on my Street Rod, but costly!

Try rust reformer, goes on easy, only has an effect on rust, it's not a paint. It looks like milk and can just be brushed on everything around the muffler end. Where there is no rust it does nothing. I taped a small parts brush on a long stick. 15 minutes effort. Lasted 3 1/2 years on my 2014 C7 Z51. Used on my Grand Sport as well.




Bottom Pic before, Top Pic After Application of Rust Reformer. It's Not a Paint.

 

Any car with a cast iron exhaust manifold is going to have some surface rust, it's just in the nature of the beast and doesn't affect function.

It's possible to clean off the rust and paint with high temp coatings of one sort or another, but I don't think this is worth it unless you're making some sort of show car.

 

There are dressings for cast-iron manifolds that wipe on and off that work pretty well. I've some around, somewhere, I used to use on a show truck (now long gone), but I don't recall the name. It was about the consistency of cake icing. Maybe someone else will come up with the name of it or similar. If I can still find it, I'll add.

Aha... "Calyx" was the name. I've not googled to see if it still exists.