I have (what I consider) a nice trick Slant 6 exhaust manifold. It's a NOS manifold with the O2 sensor provision. I had the outlet gasket matched to about 2 1/4 ". I'm thinking about Ceramic coating it. Would this make it more prone to cracking? or do you think that won't be an issue. Any thoughts....

I doubt it. The later ones with the O2 holes are highly ribbed so they don't crack as easily anyway.

Lou

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Home of Slant6-powered fun machines since 1988

So, my manifold cracked although it doesn't appear to have been leaking from the crack. The (metal) gasket was missing a big chunk by the front. I purchased a Dorman replacement manifold which took 4 months to come in. So, my question is am I better off using the Dorman manifold or having mine welded? The Dorman manifold has the provision for the oxygen sensor. It was mentioned the manifold with the "bung" is reinforced compared to the original. My car is a 1971 Plymouth Fury. I notice the studs for the engine pipe are smaller than the original manifold. I DID snap the center bolt when I separated the manifolds, and a piece broke off the heat riser spring. In the past I had a few welded with sucess and I have used the Dorman manifold as well. What is anyone's thoughts?

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"Just think of all those Ford owners who will someday want an automobile."
John Francis Dodge

Use the new Dorman manifold. It is very much worth your while to get the good gaskets for the manifolds-to-head and intake-to-exhaust junctions. And you'll need a new choke; the '70-'72 exhaust manifolds have their own (leak-prone) choke stove setup—the new manifold has the '73-up type stove. Your best bet is a № 1231 electric choke kit, assuming you are running a more-or-less factory-type Carter BBS or Holley 1920 carburetor. If you are running a '74-up Holley 1945, use a № 1234 kit.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Just curious what's a ball park price for a ceramic coated exhaust manifold these days?

74

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Where ever you go there you are!

I dunno that you can buy one already done. Have to probably buy a manifold then take it somewhere and have it done.
I will say this..... On my most recent motor buildup, I had lotsa time into it and made lots of shavings both opening the outlet to match a new outlet gasket's size plus "center" the outlet as it was way off center as compared to the gasket as lined up with both its mounting bolts. and deburring everything so I didn't rip my hands open on the casting flash.... It had busted bolts in all 3 that join the manifolds together plus both that hold the head pipe to the flange. I took it to a diesel shop near me, that is known for having a laser setup for cutting out broken bolts. Burns em out like they were never there..... blind holes stay that way.
I was quite surprised (not happily) when I picked up my /6 exhaust manifold and the bill was $150.00. I'd have just gotten another, if I hadnt already had so much time in that one....

Possible unexpected "extra" expense in building an engine......

as far as coatings I tried something different on this one, it remains to be seen how well it will hold up. I coated this manifold with "KBS Coatings" (brand name) high heat manifold paint, this company is a direct competitor to POR 15 Claims to be good to (I forget which) either 1000*F or 1200*F. Definitely cheaper than having it coated. and you can redo it or touch it up easy enough.... this stuff is supposedly "made just for" what you are wanting.

Dad Truck recently told (I think it was on FABO) of having had one coated, at a powdercoating place near him. It didn't hold up, and the company wouldn't back their job. ("no warranty") Then he did something else with it, less $$$ but also didn't hold up. Most recently, he sprayed it with a hi heat paint from Rustoleum, so far he was happy with it.
Might want to ask him.....
but just because you spend "big money" on having your manifold coated don't be surprised if it burns off, or peels.

I heard that a lot too, before when I was looking around on the web for info.

I had a pair of Chevy 283 exhaust manifolds once that I spayed back in the 80's with some not so high heat paint in a can (maybe 800 deg.), in a can was new back then if I remember right. And I didn't do the prep right and it came off pretty quick. Paints a lot better now. Prep's super important though.

I heard VHT is good too!

I was thinking of the KBS Coatings because I need to do the engine as well and you can brush it on. so I wouldn't have to pull the engine out. I haven't really thought it out fully yet. Still getting ideas.

And if I was going to pull the engine I wouldn't hesitate to do all the porting and polishing that's for sure.

74

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Where ever you go there you are!

I should have said ceramic coating an exhaust manifold these days? Old brain I guess!

74

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Where ever you go there you are!

A little over a year ago (May 2021) I asked for and received a quote from Jet Hot High Performance Coatings.
Their quote was $232.50 plus shipping. I went with cast iron manifold paint instead.

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1975 Dodge D100 225 c.i., HEI, Parallel Offenhauser, Motorcraft 2150, 904 auto, 9.25" 3.55:1

The other difference I found with the Dorman manifold is the center bolt that connects the manifolds is 3/8" compared to the original 5/16". A 3/8" bolt does not fit through the intake manifold. I have heard mention of a "nut and stud" on the center. Did the later manifold use a stud with a nut? and is it smaller at the top?

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"Just think of all those Ford owners who will someday want an automobile."
John Francis Dodge

The '73-up manifolds (including the Dorman item) do have a larger central stud. Drill out the intake manifold hole to accept it.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I thought of that but wasn't sure if there was enough to sustain that.

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"Just think of all those Ford owners who will someday want an automobile."
John Francis Dodge

in that post 27/64 for oem replacement drill intake that size

Any info on the dimensions of that stud?

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"Just think of all those Ford owners who will someday want an automobile."
John Francis Dodge