Refurbishing stock exhaust

[DMC-81]

Hi there,

I have taken my stock exhaust off to address some leaking. Aside from installing a new gasket and stud kit and a new O2 sensor, I have some questions for you all on what else you have done...

1) I read here to have the manifolds planed. I'm familiar with this as I did the same on my V8 Fiero project long ago. Question: is there a maximum or minimum material to remove?

2) What media is best or have you used to blast the the manifolds, the crossover pipe and cat?

3) Is it advisable to powder coat or ceramic coat the cast iron manifolds, or does the coating burn off shortly afterward anyway?

Here are the parts as removed today..

image.jpg

I had 3 ports leaking (#4, 1, and 3) and #4 had a poor gasket match. I'm glad that I'm doing this job.

Thanks for your input.

[John U]

I am also interested in the answers as this is on my winter project list!

Is there a good tutorial somewhere for removing and replacing the exhaust bits and gaskets?

Thanks
John

[Morpheus]

1. It shouldn't take much, the goal is to make them flat. Our mutual friend Don @ Precision Cycle should be able to take care of this for you.

2. I'm not sure what media was used on mine, I had a powder coating shop blast all my components for me.

3. I used POR-15 Factory Manifold Grey manifold paint on the headers, crossover pipe and cat. The finish has flaked off a little, but overall still looks good. I have an unopened can of this leftover from my project if you want it.

I highly recommend the one-piece gaskets for this job, as the general consensus is that they last longer. Here are some pics from my exhaust refurbishment from 2015:
DSC_2168.jpgDSC_2294.jpgImageUploadedByTapatalk1441582702.194575.jpgImageUploadedByTapatalk1441583093.203293.jpgIMG_2916.jpgIMG_2915.jpgIMG_2921.jpgIMG_2925.jpg

In that pic you posted, it looks like the left manifold is cracked. Is it that or just a shadow?

[DMCVegas]

I used POR-15 Factory Manifold Grey manifold paint on the headers, crossover pipe and cat. The finish has flaked off a little, but overall still looks good.

That looks gorgeous! I myself plan on going with an aftermarket exhaust, but I would much rather it have the color of yours. Great contrast against the aluminum engine!

[David T]

Eastwood (eastwood.com) sells the right coating for the exhaust manifold. It is made to take heat, POR 15 isn't. You don't have to have them blasted but it will look better if you do. Any good machine shop will only remove just enough to get them flat. Use Never Seize on the hardware when you reassemble. Powder won't last and ceramic is overkill and expensive and very fragile (it's glass).

[Nicholas R]

Eastwood (eastwood.com) sells the right coating for the exhaust manifold. It is made to take heat, POR 15 isn't. You don't have to have them blasted but it will look better if you do. Any good machine shop will only remove just enough to get them flat. Use Never Seize on the hardware when you reassemble. Powder won't last and ceramic is overkill and expensive and very fragile (it's glass).

You're saying that POR-15 Factory Manifold Gray (the product that Morpheus listed above) is not designed to take the heat? You should probably contact POR-15 to let them know because their website must be wrong :

FACTORY MANIFOLD GRAY is a high temp gray paint capable of withstanding extreme temperatures up to 1400F. This high temp paint will maintain a durable iron gray color and won't burn off. Can be used on all cars, domestic or foreign, and it meets or exceeds properties and requirements of MIL-C-13370.

http://www.por15.com/FACTORY-MANIFOLD-GRAY_p_51.html

[David T]

You're saying that POR-15 Factory Manifold Gray (the product that Morpheus listed above) is not designed to take the heat? You should probably contact POR-15 to let them know because their website must be wrong :


http://www.por15.com/FACTORY-MANIFOLD-GRAY_p_51.html

Unless they renamed it, the high temp product was POR 20. I have used it and the Eastwood stuff and I like the Eastwood stuff better.

[DMC-81]

In that pic you posted, it looks like the left manifold is cracked. Is it that or just a shadow?

Thanks Brandon for sharing your experience and results. Wow, that looks good. I called Don today and have been researching coatings. The left manifold has some soot in a casting imperfection in the surface. That was a port that was leaking. It doesn't look like a crack, but I'll know better when they are surface planed.

Unless they renamed it, the high temp product was POR 20. I have used it and the Eastwood stuff and I like the Eastwood stuff better.

Hi David. Yeah, in the link that Nick posted it looks they renamed it POR-15 High Temp Paint:

http://www.por15.com/POR-15-High-Temp_p_104.html

Here is the description:
"POR-15® High Temp Paint
Guaranteed to maintain rich, brilliant colors without burning off or discoloring.
POR-15® High Temp Paint is capable of withstanding extreme temperatures up to 1200°F and will resist cracking, chipping, and peeling. It is also extremely weather, salt and moisture resistant. We guarantee this to be the most uniform heat-resistant coating available anywhere. Sandblasting is the optimum surface preparation. Can be used on all cars, domestic or foreign. Meets or exceeds properties and requirements of MIL-C-13370.
Formerly POR-20, Black Velvet and Factory Manifold Gray"

This looks promising... What is the temperature that our exhaust manifolds can reach?

From my research so far, it looks like surface preparation is the key. Apparently there is a media blasting company practically right around the corner from me that does soda, glass bead, etc. and specializes in classic cars. I'll pay them a visit.

I have not had luck with even high-temp silicone-based powder coats on the manifolds; it will flake off after a short time. The crossover pipe is a different story.

As for media, I would recommend coal slag aka Black Beauty.

Thanks for the tip Matt!