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I am trying to make my intake manifold look shiny. The old porcelain is in excellent shape except that it is slightly dull and a bit flat looking. I heard that glass can be etched using hydrofloric acid as prep for top coating it with a high temp clear or gloss black (Eastwood's 900 degree caliper paint). I tried 320ing the intake and cleared it, and it looked beautiful but paint flaked off. Can I sandblast the porcelain with a mild media or acid etch such that the paint sticks? The manifold looks incredible with a clear coat, it just does not stick. With the high temp paints available I think I can make it look beautiful if I can figure out how to properly prep for paint. I could use a coarser sandpaper but am afraid it will show through the topcoat. I do not want to re porcelain as it is very costly and less durable. I do plan to drive the car daily. Does anyone have any experience with renewing the finish on an intake manifold made of glass?

Yes, glass is commercially etched using solutions of hydroflouric acid (HF); if you use it be very careful! In contact with skin, in addition to the chemical burn it has a propensity to be absorbed thru flesh by bone marrow - if you must use it, read the label warnings carefully, wear impervious gloves, safety glasses, etc. and be VERY careful.

But the porcelain is essentially glass and I doubt you'll find a satisfactory coating to improve the cosmetics that will adhere for very long. Reporcelainizing is the universally accepted method for the intake manifold and should retain it's new appearance for decades, though there are some alternatives for the exhaust if you're willing for accept a non-OEM appearance. I had my exhaust reporcelainized the first time around (about 40 years back) and the car is a driver; it held up satisfactorily for about 5 years and then began to chip and crack. They say the original factory porcelain lasted so long and held up so well because it was of a composition no longer allowed due to EPA regulations - can't verify that but surely the original porcelain was very long-lasting compared to today's materials. Second go-round on my 34 I used "Jet Coat" (I think that's the name) on the exhaust, it's a very much less expensive method that is used by the motorcycle and hot rod crowd and comes in a semi-gloss black (no gloss available, at least at the time I did it). It's held up well, though certainly not an OEM appearance. Another alternative for the exhaust manifold (for both for that matter) is "black chrome".

If you continue on the course of finding a cosmetic overcoat and you find something that will work, the world waits with anxious anticipation.

The other benefit of Jet Coat is that it reduces exhaust manifold temps. That is why it is popular with the Motorcycle folks to keep them from cooking their legs.

I had mine done three years ago by Prairie Auto Porcelain.

7208 Lakeview Cir., Minneapolis, Minnesota 55438, USA
Phone: +1-(507)-645-5325

It was $900 plus shipping, and they did the inside of the exhaust manifold with ceramic coating to reduce the heat. Still looks new.
Shipping will be costly as you need to build a big crate to protect it when you ship it. If you were close I'll would let you use my crate which I spent a weekend building.

I was advised that if the inside gets "Jet Hot" 1st then the glaze or porcelain after it should last for 12-15yrs before anything starts to show. I kind of agree since "Jet Hot" was the originator of high heat ceramic metalics from aviation and aerospace apps. FWIW $900 seems like a lot to re-glaze a manifold, but perhaps that's the going rate these days? Also was it the set or just the exhaust? It wouldn't hurt to make a support plate from some heavy angle as well to keep warpage in check. That was an issue I got sick of dealing with and that worked for me. I think it was 1/4" X 4" angle iron we used. It's been a while so...

$900 was for the Intake and Exhuast. Prairie mounts the manifold on a jig while firing to prevent warpage.

Prarie Auto Porcelain has a fine reputation and is perhaps among the best of sources for this work. Yet even with something like Jet Coat on the interior of an exhaust manifold, I can only see the job retaining pristine appearance for 12-15 years on a trailer queen. On a car that's driven even just a few hundred miles a year, I think 5 - 10 years would be about the absolute outer limit, this from lots of personal observation.

So mine has two driving seasons and about 2000 miles on the car and it still looks brand new. That's a pretty good testament.

Yes it is, and it's a tough path to take to have a stunning show car and at same time put that kind of mileage on it. Congratulations to you on that effort, I know how difficult it is.

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I think the correct term is crazy