annealing copper head gaskets

[T. Cotten]

Wow.

Does "heat flux" mean anything?

Nevermind.

....Cotten

[BoschZEV]

which oil is best In your old bike.

Well, since you brought up the subject...

By far the most important thing to remember is that any oil in your old bike is way better than no oil. If you forget that, it won't matter what brand is on the shelf in your garage.

[fillibuster]

Well, since you brought up the subject...

By far the most important thing to remember is that any oil in your old bike is way better than no oil. If you forget that, it won't matter what brand is on the shelf in your garage.

Thanks to all of you who commented, I appreciated every word of it. Sure, I got a few smiles out of it, but that was very much like the challenges offered by classmates to the teacher. That wasn't out of line then, and it isn't now, absent any malice, in or out of the chicken coop! ...... thanks for a civil exchange.

Now as to my convictions: I'm satisfied that both cylinder and head surfaces are flat, but not smooth. As I mentioned, they have scuff scratches, from the large belt sander used on many automotive heads. If a head gasket were made of a sheet of hard steel, these scuffs would leak air from the cylinder, I feel. So you have to understand my concern about which material would better fill in the minute voids apparent in the scuffs. I can't help believing that the composite would more likely accomplish this than the copper. I also believe that rattle-can copper-coat on the composites helps this even further.
If I had cast-iron heads and a guaranteed no-gaps fit to the cylinder I'd be a hands-down believer in the copper, and I have another reason for my preference of the copper: The cast-in-India rear cylinder's bolt-hole placement is poor enough that I had to hog out 7 of the 9 gasket holes. I might not get so lucky hogging out the composites.
So thanks again on the discussion. ................. I wasn't supposed to pick a winner, was I?

[gww]

evening, looks like the party is about over. not sure i could add any more other than what has worked for me so far. on the 30 chief i plate lapped the head and cyl. surfaces. started out on my lapping plate but after a half hour of figure eights and my arms not getting any larger i ran to town to do them on a automatic table. before i assembled the heads to cyl. l laid the gaskets on a 1/2" plate and put a torch to them just till they turned dark and let them air cool. i also own a 2002 chief w/ aluminum heads and have done this same process to it. the 02 has about 76k total miles on it and about 45k on the last time i was in it. back to the 30 chief. i did have the rear head off 3 times during the coast to coast ride do to valve and spring problems reusing the same gasket each time, being middle of night or morning while assembling in parking lots and one under a tarp in a pretty good rain all i had was a tube of high heat copper silicone, i applied a thin coat each time. dont know if this would help anyone, but it worked for me. copper good. fire bad.

[BoschZEV]

i did have the rear head off 3 times during the coast to coast ride ... reusing the same gasket each time, ... tube of high heat copper silicone, i applied a thin coat each time. ... it worked for me.

At the risk of getting too technical for most people's interest, I doubt if it is necessary to re-anneal a Cu gasket in most cases. It's just that it's so fast and easy to do that I've never not done it, as you were forced to not-do during your cross-country run. I also don't think the silicone did you any good, although clearly it didn't do enough harm to cause problems.

When any metal is subjected to a compressive or stretching stress (force) it strains, i.e. changes its dimension (strain is the change in dimension per unit length). Thinking about a material as atoms connected to each other with springs, the springs compress a little under a compressive stress. If the applied stress isn't too large none of the atoms are forced out of their relative positions and the springs fully recover their original lengths after the stress is removed.

A ductile material like annealed Cu strains a lot for relatively little stress and so it doesn't take much stress before atoms are "permanently" displaced from their original positions and the completely elastic behavior is lost. When this happens, the material does not return to its original length after the stress is removed. However, it's not all or nothing. Even if the applied stress is two or three times the elastic limit much, but not all, of the original dimension is recovered when the stress is removed.

OK, now to apply this to motorcycles. If the head gasket were pure Cu without any impurities or alloying elements the elastic limit would be ~1500 psi. For impure Cu or an alloy (which is likely the case for a head gasket) it would be higher. Completely coincidentally, peak combustion pressure in an internal combustion engine is ~1000-1500 psi. Since the heads don't pop off when our engines fire we know the clamping force supplied by the bolts is at least this amount. Knowing the number of bolts and torque settings it would be possible to calculate the actual clamping force for a given engine but for present purposes let's assume the heads are clamped down at twice the combustion pressure, ~3000 psi. This value is not all that much more than the elastic limit of pure, unalloyed Cu. What this means is very little "disruption" of the Cu crystallites will have taken place when the head was bolted down, so it will have retained nearly all of its ductility (softness). So, it should be reusable without having to re-anneal it.

As I said, even though the science says it's probably not necessary to re-anneal a gasket, it's so fast and easy to do I always do it. Five minutes with a torch and bucket of water vs. even the small chance of having to rebuild the top end if the gasket leaks makes re-annealing the only reasonable choice. Unless you're in a dark parking lot 1000 miles from home and without a torch, in which case the above science tells you it is a good bet you will be able to reuse the Cu head gasket without problem.

So, you didn't get lucky when you were able to re-use your solid Cu head gasket three times, you benefitted from the fact combustion pressures fall fairly low on the stress-strain curve of annealed copper. Still, I recommend re-annealing if rebuilding an engine anywhere but in a dark parking lot.

[Peter Cooke]

At the risk of getting too technical for most people's interest.....

Hell no, keep it coming. This is very interesting, and useful, information.

[fillibuster]

Okay, so, I did it. Annealed both gaskets, with oxy-acet, first gasket with the cutting head on a Smith 509 (the small one), second time with rosebud.
First gasket, spent 3x the time as 2nd, passed over the entire gasket, warming it with the torch head about 2" above the work. (The gasket was placed on a 1/2" steel plate). I didn't know how quickly things would heat up to dull red, so I slowed my motion until I could tell it was getting there. But I had to concentrate the heat more, dwelling on an area and moving very slowly, letting the copper warm up to dull red and moving forward and aft a little. The color of the copper makes it very difficult to catch the dull red, and I melted the outer edges in two places (had to file them down later). I caught myself getting the head too close a few times, about an inch, and things got orange to yellow, and I had to back off especially near the bolt holes. The bolt holes is where the heat can get dangerous. But I got through it, scrubbed it with scotch-brute, filed the bubbles down, then realized how soft and pliable the copper had become. I could bend it between thumb and index/middle finger.

I did NOT flip the gasket over and repeat, and must say that the underside had a different appearance, as if it had not been treated.

The second gasket I switched to the rosebud, which has less of an oxygen blast, and things went a lot quicker. I made about 6 circular passes, then put the heat to it, watching closely, but still got a bubble or two from too much heat. Saw orange more than once. But I'll call the second gasket a little more of a success than the first.

I must say that the cleanup and filing and sanding (yes, did a little sanding on a flat plate) made it a chore that I might choose to buy my way out of, except that:
When these gaskets were new they were nowhere near as soft and pliable as they are now. The difference is as between soft tube in a coil and hard copper that would kink if you tried to bend it. So, I'm tempted to suggest that NEW GASKETS should be annealed before installation.

For those of you who've tired of this thread, I apologize, but in the interest of what's practiced (while much is preached), I had to share, whether it proves my wisdom or my dumb luck. The results are hopeful educational.

Oh, btw, how about a show of hands: all who have annealed copper gaskets please acknowledge.

[NiteOwl]

Oh, btw, how about a show of hands: all who have annealed copper gaskets please acknowledge.

Yes, I do so in my job very often. I have really appreciated the explanation given here about copper and the process and the difference in hardening steel. Thanks!

Bob

[rousseau]

It was suggested to me at one time to anneal new copper gaskets. The reason given was, when they are "stamped out" this will work harden (temper) the edges and the bolt holes.

When you laid your gasket on the steel plate it acted as a heat sink. I simply hang them from a wire. I also do it in very low light. Makes it much easier to see the glow.

Jewelers use a solution of powdered boric acid and denatured alcohol to coat the precious metals when annealing. This helps to keep the oxidation to a minimum. Cleans off with hot soapy water.

I have enjoyed this thread.

[fillibuster]

I believe the heat diffused throughout the material sufficiently; the underside's appearance may have been a result of the minimal air exposure, or the carbon from the acetylene (I used a normal flame).
Odd, when I started out with a wire, the wire, a 1/8" welding rod, took on color too fast for me, and the flow from the torch just spun the gasket around. With the plate, everything stayed flat.
Dim light, I won't forget that. Many times, especially with new employees or those in a new experience, people tend to breeze past considerations that would ensure a better job in more ideal conditions. It takes a little effort and a mature man's patience to persevere without breaking a sweat, but I feel it's worth the effort. No, it doesn't take effort to turn down the lights, but I avoided changing to the rosebud for the first effort.
The boric acid/denatured alcohol: something the copper is dipped into? brushed on? wet? dries away under the torch? .. does it stink?

[fciron]

Filibuster, sounds like low light would help a lot and could have saved you some trouble. I work with sheet copper quite regularly (haven't had to anneal any gaskets yet) and I get good results with a propane torch, no melted edges, no sanding, not enough fire scale on the surface to worry about.

It seemed like there were a couple good explanations and I try not to be repetitive. However, since you melted bits of your gasket, I'm going to explain my process, since it seems quick, easy, and safe to me. I use a couple of old firebricks to support the part or I just hold it with pliers and do one half at a time. If I take the time to turn the lights down, I heat the copper to only the slightest hint of a red glow, but brighter light I will watch the oxidization colorsand the wash of the torch coming off the work, when it turns orange I can be fairly sure the piece has reached annealing temperature. (If I recall the explanation correctly, the orange is the CO2 in the torch flame incandescing which occurs at approximately the right temperature.) The torch wash will also turn orange if the firebrick supporting the work reaches that temperature, so some attention is needed.

I found this video on an jewelry/art metal site, if you jump to minute seven you can see her anneal some copper in bright light and her explanation of the color cues is pretty good. I think you'll see she doesn't get anywhere close to melting the edges. http://www.ganoksin.com/benchtube/vi...eal-Your-Metal

[pisten-bully]

Brand new I put them in the oven before installing. 2nd time around I used a mapp gas hand torch. Reading this all here I'm sure the oven method was purely for my own satisfaction and served only to anneal my cautious side! And they're on the bench again, and I still have gas in that mapp cylinder, so that's what I'll use again.

[fillibuster]

Brand new I put them in the oven before installing. 2nd time around I used a mapp gas hand torch. Reading this all here I'm sure the oven method was purely for my own satisfaction and served only to anneal my cautious side! And they're on the bench again, and I still have gas in that mapp cylinder, so that's what I'll use again.

I think I'll use the rosebud again, if I can find the smaller one. The cutting head took quite a while to heat it up, so by that experience I do believe it takes serious heat. Those gaskets are .060" thick, nearly 1/16". ..... but I'll find a dark corner.
I recall the "wash" effect, and working with that. The red came on with that, and the orange popped in several times too.
So the wash is all I need?

[fciron]

The wash turning orange is hot enough.

Ambient light has a huge effect on the apparent color of glowing metal, which makes it a poor way of communicating temperature. The dull red needed to anneal copper is nearly invisible in a decently lit shop, while the "cherry red" often cited for hardening steel is much closer to orange when standing at my forge.

[fillibuster]

The wash turning orange is hot enough.

Ambient light has a huge effect on the apparent color of glowing metal, which makes it a poor way of communicating temperature. The dull red needed to anneal copper is nearly invisible in a decently lit shop, while the "cherry red" often cited for hardening steel is much closer to orange when standing at my forge.

Forge, that has been on my mind too. I haven't lit mine in years, but I thought of it and how it would have been more of an even heat throughout the work. But it's also been said that coal is a dirty heat. Would that have been a bad idea for copper? Or not?
My old home-built forge has a rheostat-controlled fan, and it's heated some big irons. Shame to fire it up for a few silly gaskets, huh?
What about a gas-stove burner? The flame would be fairly well distributed. ........ We don't all have oxy-acet, so it's still legitimate to ask, right?