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Porcelain exhaust manifold suggestions

Started by LaSalle5019, July 14, 2020, 11:46:26 AM

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LaSalle5019

I rebuilt the engine in my 1939 LaSalle and, since the car is close to show quality, I figured I would make the engine compartment correct so had my exhaust manifolds porcelain coated by one of the reputable companies that gets mentioned in this forum.  After initial engine break-in and tweaks in the garage the porcelain looked great but after the first drive, where I was actually making power, much of the porcelain popped off. And only in certain sections. What a mess â€" small pieces of porcelain all over the engine.  The company asked about being too lean â€" I’m definitely not as I’m planning to play with my WDO carb to lean it out as my exhaust is sooty and I’m only getting around 9 mpg.  They offered to redo the coating which now brings me to my dilemma. It is a real pain to pull off the exhaust manifolds, package and ship them out and then reinstall them. My concern is will this just happen again? Are they just going to run them through their same process and hope for better results?  I don’t want to have to do this again so I’m thinking about just taking my losses and doing ceramic coating.  I understand you can get a decent semi-gloss finish (not quite correct) but the coating is very durable.

Have others had issues with porcelain failing or success with ceramic?

My before video -  https://www.youtube.com/watch?v=POdl9US1NpA
and you can see my after photo here.

Thank you for any advice.
Scott

fishnjim

AKA; spalling.   
I'm not a pre-waree, so not familiar with this manifold.   Some of these were factory coated.   
I'd use a more "advanced" formula for the coating than what's "stock".   They have to prep the metal correctly or gas gets under the coating during baking.   I used a local company(NC) and they did great work.   Even had leaks drip on it, sizzle, and looks like new, but it's a grey cast iron look alike, not shiny black.   I bought a spare set and had them coated, just in case.   So maybe an idea to ponder.
I have tons of experience with glass lined equipment, so spalling is not a given, but does occur often enough, but can be made to last.   A splash when hot with cold water(thermal shock) would be disastrous.

jackworstell


   Fishnjim

..........the name /type of coating you used ?   I take it than it was not  porcelain  of some type ?

Jack Worstell

harry s

I've had the same experience with porcelain coating. I have used several different vendors and had the best luck with Prairie (maybe that is who you used). They also do an inside coating which is supposed to help with keeping the temp down. Timing along with too lean a mixture can do it too. The manifold temp on my car at operating temp is around 400 and the coating has held up so far. I'm not sure at what temp porcelain fails  but it happens like a rock through glass.      Harry
Harry Scott 4195
1941 6733
1948 6267X
2011 DTS Platinum

Tom Beaver

The porcelain used on the original manifolds contained lead, to make it slightly softer and more malleable so that it could withstand the thermal expansion without it spalling off.  A few years back the EPA told the vendors that they couldn't use lead anymore so the "new" porcelain is not as good and many times has issues.  When I had the manifolds for my 38 redone I took them to a place that sprays a ceramic coating on the inside and outside of exhaust headers and other car parts for race cars and hot rods.   The material acts as an insulation to cut down on heat transfer as well as inhibiting rust.  It comes in several colors and the black, which they put on my manifolds, is a mat color with a slight sheen but certainly not shiny like the originals.  It seems to work well and I have had no issues.

Tom Beaver

39LaSalleDriver

Not that I have much to add, but in investigating porcelain for mine I was not excited by the prospects. Most reviews I read indicated disappointing results overall for re-porcelainizing headers. I have taken to just using BBQ paint and touching it up every so often. No, it doesn't look right, but it's a heck of a lot cheaper for the disappointing results it yields. Maybe some day I'll find some which fit my car that has most of the porcelain intact.
Jon Isaacson

1939 LaSalle 5019