Macneish Exhaust manifold re-skin

[Ian S.]

Hi,

Has anybody had this done to their exhaust manifolds recently? How close to raw cast iron do they look when done? Are there any problems that can result from it either to the manifolds themselves or when trying to reinstall?

Thanks,

Ian

[Joe L.]

Re: Macneish Exhaust manifold re-skin

Ian-----

Yes, I have. The process for the exhaust manifolds involves jet-coating of the manifolds (brilliant white). Several cans of high temperature cast blast paint are supplied with the instructions that you apply a full can to each manifold OVER the previously jet-coated cast iron.

The finished manifolds look VERY close to natural cast iron. Of course, the cast blast does look very much like cast iron but the issue is will it hold up? I haven't gotten to that stage yet, but I know of quite a few folks that have and they report excellent results and durability. So, I'm looking forward to the same. Personally, I don't think that there's anything BETTER that you can do to maintain original-looking, rust-free manifolds. So, while this process might not be perfect, it's about as close to perfect as you're going to get.

The only problem that I have heard of is that the manifolds often have a bit of "over spary" jet coating on the flange surfaces. This is true; mine do have this. However, I don't think that it will represent any real problem and I plan to remove it with a 3M abrasive wheel on a drill before I install the manifolds, anyway. I don't think it will be difficult, at all.

[Ian S.]

Re: Macneish Exhaust manifold re-skin

Joe,

Is this like a Jet Hot coating? I don't quite understand how it protects better than just using the high temp cast blast. Wouldn't the paint wear the same or do you think the coating actually makes the manifolds cooler and thus the paint lasts longer?

I asked someone at Macneish about it and he would only tell me that they use a "secret" process. I thought the manifolds came back with a finished look, I didn't realize you had to paint them. Does the coating make the paint look different than if you were to use the same paint on raw cast iron?

[Joe L.]

Re: Macneish Exhaust manifold re-skin

Ian-----

Without the "jet coating" underneath, I don't think that the high temperature cast blast will hold up on the manifolds for very long. I've never found any paint, including the supposed "very high temperature" type, that would. However, I'm told by those that have had this process done that it does hold up when used in conjunction with the "jet coating".

The paint does not look any different, to me, when it is applied over the "jet coating" than it would if it was applied to the plain cast iron.

Frankly, I was a bit surprised that the manifolds were sent back to me with just the "jet coating" and the instructions to apply the VHT cast blast paint supplied. I figured that they would have applied it before sending the manifolds back. But, at least in my case, that's not how it happened. No big deal, though. I like to paint, anyway.

In fact, I e-mailed Jerry and asked him if it was best to apply the paint just before I installed the manifolds on the car (since it was going to be quite some time before I was actually going to use them and I figured maybe that was why they didn't apply the paint). He told me that it was fine to apply it right away, even if I wasn't going to install the manifolds for quite some time.

[Paul Reynolds]

Re: Macneish Exhaust manifold re-skin

I got mine back from Jerry a couple of weeks ago. I believe the process he uses was called "flame spray" back in the old days. I had several sets of headers done this way around 30 years ago. I believe it is molten aluminum sprayed onto the manifolds. It seals the cast iron against the elements preventing rust.

I too had some overspray on the flanges which had to be knocked off. After painting, they do look new.

[Clare Carpenter]

Re: Macneish Exhaust manifold re-skin

Jerry did a repair and reskin on my aluminum manifold. The repair was a redo of a previous poor looking but functional repair, done elsewhere. Jerry's work is top notch. The manifold looks new and the repair work is close to invisable.

I talked to him about doing my manifolds. I believe he said the process used is a spray weld technique using aluminum to coat the cast iron. It is applied very thin so it does not alter the cast iron texture like Jet Hot, which is a ceramic based coating. I haven't made up my mind whether I'm going to do it. It's not cheap but it is apparently long lasting. According to Jerry, the key to the VHT paint is baking it on and of course the aluminum base coat, which won't rust.

Paragon has a new coating, "self applied" that they claim will last years.

[John H.]

Re: Macneish Exhaust manifold re-skin

Here's what iron manifolds with Jerry's process look like after three years and several thousand miles; no rust, no flaking, no problems ('69 Z/28).

[Justin N.]

Dry Exhaust manifolds

I had my curret production GM 2 1/2" manifolds ceramic coated to aid in original-looking finish. I later put them back in the original boxes, which got wet from extreme rain storms this last winter, the shed flooded! I have little rust pits showing through the ceramic coating, I think the raw cast is VERY porous. I would make sure Jerry's products don't get wet in any way. It seems rust always has the upper hand, maybe it's just the salt air, I can't say for sure.
Justin #41362

[Mark #28455]

Things that make you wonder

Isn't it odd that the NCRS deducts points for all sorts of non-original stuff like paint too shiny, cast blast on differential, etc. but we're trying to paint the exhaust manifolds? I know the originals are rusty and ugly but ANY manifold that isn't MUST have some kind of non-original coating applied.

Mark

[Clem Z.]

he is most likely using a "METCO" gun.

it is a device that uses ox/acy to supply the heat and you feed different types of wire as the base metal you want to coat with and it sprays the molten metal on the substraight. neat piece of equiptment that shoots fire and make noise. i worked with one years ago at a small shop a relative owned where he took worn parts,built them up using the METCO gun and then we machined them back to the correct size.

[Tracy C.]

Re: Things that make you wonder

Mark,

I'm sure coated /painted manifolds will also get hit with a deduction, but for some, the added protection to the part is worth a point or two. Others may have the car judged "in the raw" and then opt for some protection from the elements after they get the ribbon.

I'm just going to remove and replace my "ginnies" with some jethot/castblast ones after the big event.....someday, if I ever get there....I promise...

tc

[Mark #28455]

nobody ever accused me of NCRS correctness

Don't worry, I won't tell on you!

Actually, I've been rebuilding my big blocks as 489's (4.25 stroke) to make up for the power lost by dropping the compression to 9.5-10:1. That way they still pull hard to 6500 RPM and run great on 93 octane gas.

HAVE FUN, that's what it's all about!
Mark