Removing a refractory gasket; gasket removal solvent?


#1

The gasket on the carburetor seat is as good as bonded. (The air horn gasket came off whole, looks good enough to re-use, which I didn’t). I’ve scraped for an hour, dissolved what I could with carburetor cleaner, tried every other nasty solvent I have on hand. All the fiber is gone; I’m down to a shiny brown layer - it looks like varnish.

A few places on-line mention ‘gasket removal solvent’; one mentions Loctite brand, of which I can find no mention on loctite.com. I can’t find any at the auto stores.

Any advice?


#2

https://www.permatex.com/products/gasketing/gasket-removers/permatex-gasket-remover-low-voc-formula/

Tester


#3

Hmmm… neither AutoZone nor the Pep Pill Boys carries it; Advanced Auto Parts has it; all 5 reviews are 1 star Reviews of Permatex Gasket Remover @ Advanced Auto Parts


#4

Single edged razor blade scraper. Used carefully, should get the job done.


#5

I found this instructional video from Permatex about how to use their
gasket remover. You have to remove the fiber first - it’s for the
shellac that some gaskets have. Perhaps the plaintiffs tried to use
it to remove the fiber.
https://www.youtube.com/watch?v=iF2my-oganM

Unfortunately it does me no good: it does nothing to the shellac on my engine.

I had no problem scraping fiber gasket off my carburetor with a razor
blade, but the engine is alumin(i)um - vulnerable to scraping by a
steel blade. And I’ve already scraped off the fiber layer; I’m down
to shellac, invulnerable to scraping. I can catch an edge and cause
chip to break off, but it won’t scrape.

A clerk at Advance Auto recommended brake cleaner - we all know how knowledgeable auto-store clerks are.

One of those gasket grinders? Some think they’ll damage alumin(i)um.

Can I leave the shellac on? Will the fiber gasket compensate for its
(minor) unevenness?


#6

I had that problem last time I rebuilt my truck’s carb. I used a combination of an old credit card, & razor blade scraper per @Mustangman 's suggestion, and I tried various things to dissolve it, but I think I ended up using plain old gasoline as the solvent. It was a fairly time consuming and awkward job as I recall. One good thing about doing this tho, while working in the area and everything in the way removed, I was able to see the part number info stamped onto the intake manifold, which is useful thing to know when verifying parts compatibility issues for Ford engines. They even have the spark plug firing order stamped on the intake manifold. I expect if you can find the commercial gasket solvent , that is the best and safest solution.


#7

I’m confused. You say the gasket for the carburetor seat is bonded on and you’ve gotten rid of all the fiber, but as I recall the seat gasket is nothing but a small crush washer. Once you unscrew the seat the sealing washer should come right off with it. Whatever residue is left on the underside of the air horn should be easily removed with a pocket screwdriver.

Do not use any kind of mechanical grinder on any carburetor piece.


#8

Small? It’s about 5x3. The fiber crush washer scraped off with simple scraping and a few rounds of carburetor cleaner to dissolve difficult parts. Underneath the fiber washer is a layer of shellac I’ve found impossible to remove with scraping and solvents. It won’t scrape off at all.

I found it at Advance. I used it. It was useless, as all the other reviews reported. Permatex’s video shows it removing shellac easily.

Could I leave it? It’s sturdy; the carb was put together with it there; if it’s lasted 30 years, it’ll last another 30. What is the risk? How poor could the seal be? Why was shellac used in the first place?


#9

If it’s smooth, leave it there. As long as the gasket seals, why not?


#10

That’s my question. I’m a non-expert. This is my first carburetor re-build. I’ve seen only fiber gaskets before, didn’t know about shellac gaskets. Permatex sells a shellac to be used for gaskets, so it’s a thing. What purpose does it serve? Was it meant to bond the fiber gasket to the engine (it’s only on the engine, not the carburetor)? Would the best, professional, repair be to remove the shellac completely, apply a new layer, stick on the new fiber gasket? If it’s a separate layer instead, the one already there seems to do the job; if it’s meant to stick to the fiber gasket, it’s not. Where can the fiber gasket go with a carburetor bolted onto it?


#11

I’d be surprised if Berryman’s carb cleaner wouldn’t remove it. I wouldn’t do a rebuild without soaking in that stuff anyway and I’ve yet to have anything other than metal stand up to it (even that can be damaged if left soaking too long).

A backwards drag of the razor blade will remove even a small amount of the metal so it’s often effective at scraping off residual gasket material. But you need to be careful doing it.

I’ve also used scotchbrite pads, they come in various abrasive levels just like sandpaper but are far less destructive.

In the end, anything stuck to the surface that stubbornly only needs to be flat enough to seal the new gasket. It’s a carb base, not a rocket o-ring…


#12

The seat is the small, approx. 1/2" diameter, part that the needle fits into to stop the flow of gas into the carb bowl. It sounds like you’re not talking about the seat but rather the carb base gasket, where the carb mounts onto the intake manifold.

It doesn’t need to be shiny clean, just smooth enough that it feels flat to your bare finger.


#13

Hadn’t heard of this brand. I’m talking about the gasket that was on the engine, where the carburetor attaches to the engine. I assume you don’t soak your engine in carb cleaner.

Yes. I thought I described that clearly.


#14

One more vote to leave it alone, and go ahead with the new gasket and installation.


#15

I understood it was the carb base gasket. I have removed and replaced many of them without a problem. I have never heard of a refractory gasket. What is it?


#16

You have a one sided view of the world? Of course you can soak the surface of the manifold, you simply brush the cleaner onto it and maybe repeat a few times to keep it wet while it does its thing…


#17

Maybe try fine sandpaper on a flat surface and gently gyrate the carb base against it.


#18

Not sure what that means exactly. But on my truck there’s two gaskets in that area. One is between a 1/2 inch metal spacer and the intake manifold, and the other is between the spacer and the carb. That spacer hold the egr valve, and hot exhaust gasses go through that spacer and the gasket under the spacer is involved with all that. So that under-spacer gasket really takes a beating, and seems to be made of a different type of material than the one under the carb. In fact the under-spacer gasket didn’t come with the carb rebuild kit, I had to order it separately. That under-spacer gasket was what was causing most of the poor engine performance & idling issues w/my truck; once exposed I discovered it had a big hole in it where the EGR gasses had burned right through the gasket material, creating a huge vacuum leak directly into the intake manifold. So calling that type of gasket a refractory gasket sort of makes sense.


#19

‘Refractory’ means ‘hard to break’. It’s used technically for hard-to-break materials (such as boron nitride analogues of diamond, nearly as strong, much cheaper); in chem lab there’s a ‘refractory thermometer’ to measure temperatures higher than mercury thermometers can take; it’s used for difficult people, particularly children; and many other uses. It isn’t a technical word specific to gaskets.

I wrote that I did that, many times, without success.

I’m talking about the gasket on which the carb rests. I hadn’t notice that it’s sitting on a metal plate. I hope the gasket underneath that plate is okay.

I didn’t bother further. In the light of day I could see that the shellac is a very thin layer and smooth. I wasn’t confident before I asked that I could get away with leaving it. Thanks all.


#20

Not all carb’s use that spacer plate. On Fords it serves two purposes, first, a place to bolt the egr valve, and second, it reduces the amount of heat transferred from the engine to the carb. That’s helpful in preventing hard to starts when the engine is hot. I think it probably has another a minor benefit too, allows a little more time for the gas and air to mix better before entering the cylinder.