Reusing Solid Head Gaskets

[LJ.]

Richard... Yes I remember now the disapointments you had with the head being skimmed that left a poor surface and the need now for the imperfections to be filled by a well annealed gasket. I've had a brain wave!...

With us reading about the use of 'two' gaskets recently I wonder if you could use one thicker copper gasket...? Instead of the normal 2mm size gasket, maybe a 3 or 4mm, the thought I had here is that a greater thickness of annealed copper might result in a softer gasket that would fill the imperfections better than a thinner one would. (I'm having a job in putting this across in a written format) Hope you see what I mean.

[Beezageezauk]

A10Boy,

Yes, I did the write up especially for the BSAOC Mag but I,ve posted it in the "Stories & Chat" section of this forum for all to read.  For the benefit of this forum I think I've entitled it "Why 2 Head Gaskets?" but originally it was called Challenges of the Isle of Mud Rally.  Unfortunately I couldn't add the photographs here for some reason.

Again yes, the engine is running with a 7.25 and a 6.75:1 compression piston fitted but that alone shouldn't give me this particular problem.  Obviously it must be a variation of the gudgeon pin (wrist pin) to  piston crown heights that is causing it.  Anyway the engine will be pulled down over the winter to have replacement pistons, cam followers and camshaft fitted.  Then hopefully only one gasket will be required and the annealing process will be repeated.

How's that for getting back onto the thread??

Beezageezauk.

 

 

   

[A10Boy]

The best Ive ever seen LOL

[RichardL]

A10BOY, There seems to be a general opinion that new gaskets are not soft enough to deform to the imperfections of heads and barrels. I know everyone else's bikes have no such imperfectuions, but mine does. Of course, the gasket won't take to every scratch and knick, as you won't get that kind of force without driving the bolts through the head or twisting them off. I'm just looking for a mild flow due to broadly applied force. The question of new or used has, I think, become irrelavent in the annealing issue. I have, indeed, ordered a new gasket and intend to compare it with one I've annealed.

Following up on the experiment I showed on 9 Dec '08, and as noted in the above qoute from 11 Dec, I have tested a new SRM head gasket without my own annealing versus two others after various annealing methods and states of use. The one thing I changed in the experiment was the amount of observed deflection (from 1" to 1/2") to avoid work-hardening my new gasket.

1) Once-used, fireplace annealed gasket as shown on 9 Dec (not reused after annealing): Avg. for 1/2" deflection = 432 gm.

2) Spotty, propane-torch annealing job after removal from from engine due to leakage and no further annealing: Avg. for 1/2" deflection = 626 gm. I think this is, clearly, work hardened.

3) Brand-new gasket from SRM with no further annealing: Avg. for 1/2" deflection = 418 gm.

So, the good news is that the stock head gasket, at least this one, does not need any further annealing.

Attached below is a photo of #2 (referring to the above item, but the colloquil definition applies, as well). It is rather obvious by the venting tracks why I was leaking oil at the barrel/head joint and experiencing hard starting and questionable performance. A caliper on the gasket showed the venting tracks to be 0.002"-0.004" thinner than the areas that obviously sealed. I assume the difference in thickness was due to the erratic annealing method.

I hope this is interesting.

Richard L.

[unclemeat]

Just to add to this discussion...I'v also had many heads in the past with a certain amount of imperfections, so... after annealing the copper gasket, i put a really small amount of GREEN HERMETITE (this stuff is not to be confused with the other types of gasket sealant as it sets rock hard) on both sides of the gasket. It fills those little irregularities and seems to do the job with no leaking head joints.

[BSA_54A10]

Well I will add my 2ps worth here.
Copper will absorb carbon at elevated ( red) heats.
The hotter the copper the more carbon that gets absorbed.
If you manage to get enough carbon in there you will end up with a copper-carbon alloy referred to a "tough pitch" copper.
This alloy will have high carbon hard spots and as such is not particularly suitable for use as a gasket where uniformity is essential.
Heating the gasket in coal file will definately cause carbon to be absorbed.
If you have to use such a heating device then it is best to use coke rather than coal as the former releases far less free carbon during the burning process.
Commercially foundries pouring pure copper and high copper alloys ( without zinc) use charcol as a flux to prevent the formation of tough pitch copper.

If heating with an oxy torch then you should set it to be a little on the lean side ( excess oxygen).
If you are using an air/propane torch then you should do it in a small furnace and use reflected radiant heat ( heat the bricks red hot). A simple furnace can be made from a couple of fire bricks top & bottom with some 1/2 bricks to make the walls. I use old broken bricks from the lining of my wood stove, which are readily available & quite cheap.
Such a simple enclosure will easily attain 800 deg C with nothing more potent than a disposable propane torch or even a gas ring running towns gas.

About quenching.
In theory it will make absolutely no difference how you cool the annealed gasket as the copper has a continious phase from red hot to room temperature so there is no phase change to surpress ( or induce)
In practice you have to be careful if you quench as you can set up thermal stresses if the quenching is not done properly.
Usually I pop another fire brick on top of the gasket after I have finished annealing to ensure a slow & even cooling.
A full soft gasket will be indented by your thumb nail and is what most copper mills use to quickly check sheet stock is full soft as doing a proper hardness test on thin copper sheet is a bit tricky.

About cleaning.

Copper should be cleaned in an reduceing acid such as Nitric acid or acetic acid ( vinegar  ) or even citric acid .
However the powers in charge have scheduled Nitric acid in most countries so we "terrorists" can not make nitro- glyserene but citric acid is available from most good cookery suppliers.
Mechanical cleaning with things like wire brushes should be avoided as it will induce work hardening.
Polished such as autosol will work quite well & not upset the apple cart as will things like chemical cleaners for Stainless steel pots.  Steel wool will also work quite well.

Hope this helps to clear things up
Bike Beesa
trevor

[bezabill]

that was a good and well spent peny,s worth,s LOL

[RichardL]

Trevor,

Thanks for the excellent technical advice. Do you think the ash wood used in my fireplace would supply carbon similar to coal. It doesn't really matter, because, if I try this again, it will be with your propane torch and firebrick method. I was not able to impress my thumbnail in the new SRM gasket, but I am convinced it is a tiny bit softer than the fireplace-annealed version.

Regards,

Richard L.

[A10Boy]

Thanks for you excellent post Mr BSA_54A10.

A caliper on the gasket showed the venting tracks to be 0.002"-0.004" thinner than the areas that obviously sealed. I assume the difference in thickness was due to the erratic annealing method.

I dunno for sure but I would have thought that this was caused by scouring due the escaping gasses.

[BSA_54A10]

Ash by its very nature is carbon deficient so it will not lead to carbon pick up.
It is also highly alkaline so if left in the ash to cool down should come out relatively clean.
Gaskets as supplied are never full soft.
This is because they are pressed from semi hard ( cold finished ) plate.
Trying to blank full soft copper is very difficult as it tends to extrude rather than shear cleanly, jambs in the presses and is a regular PIA for the manufacturers .
Grain growth is not a problem for a gasket as it is in compression and being copper ( with FCC crystal structure) the actual grains are weaker than the grain boundary in the first place.
It dose become a problem if using extra thick gaskets ( or several) to lower compression or on really high compression engines ( particularly with blowers ).
Bike Beesa
trevor

[RichardL]

Maybe reaching the end of the story on annealing my head gasket. (I can hear our well experienced members, "much ado about nothing," or the like.)

Heeding Trevor's comments that a truly soft head gasket will deform with a thumbnail and, also, that new gaskets can't be maximally soft, else they can't be stamped, I set out for another bit of interesting information. Specifically, I called SRM and asked them if they further anneal their gaskets before installation, and the answer was "yes."

So, I annealed my brand new gasket with a MAPP gas/oxygen torch and was able to create a nice moving red glow. Referring back to my 8 February post, whereas the new gasket took an average of 418 gms for 1/2" deflection in my setup. After annealing, it only took around 225 gms. and could be dented with my thumbnail.  'nough said, it's already in the bike and waiting for rocker covers to go on next. One thing I forgot to do before yanking the bolts down to 40 ft. lb was to check my tming. Now I'm going to need to get creative with some kind of calibrated depth gauge, as has been discussed at length in the forum. I am up for working out the depth gauge, rather than doing any dismantling for using a degree wheel.

Richard L.

[groily]

This all amounts to great confirmation of the state of affairs, as well as being a wonderful pyrotechnic interlude.
I was fairly sure that new copper gaskets needed annealing to get them softer for all the reasons expressed - or anyway, I always have - and the deflection/thumbnail tests and word with SRM prove it.
I certainly annealed mine - from SRM - when it went on, and no problems at all, plus check-tightening proved to be unnecessary, although I did it anyway. I don't go as far as 40 ft lbs - and that with an iron head - as I reckon 34 ft lbs ought to be enough. BTW, the alloy heads of another marque in the shed are only meant to go down to 18 ft lbs - and the studs hold the cylinder barrels on too. But they're only 5/16th Cycle nuts on long studs (which rather encourages me to obey the book of words!). . .  Point is, cleanliness plus sensible design and careful assembly enable them to withstand pretty much the same fiery furnace as pertains in an A.

[RichardL]

Groily,

Having used 38 ft. lbs. in the previous assembly, and experiencing pressure and oil leaks, I opted for 40, as mentioned by David. However, the last gasket was not as soft. It makes me wonder if the head will warp between bolt holes as the gasket is compressed. Also, I suppose there might be some deformation of the alloy under the washers, but I've tried to hedge against this by doubling-up on hardened washers of the maximum possible diameter. I'll know more in the, hopefully, distant future when the head is next off. As for snapping the bolts, so far, so good.  In any case. it's not like I can now go back and loosen them to a lesser torque. All these fears aside, I'm hoping to have the same positive results that David (and others, I suppose) have had when using the 40 ft. lb. value. 

So, I ask myself, "why didn't I ask SRM what torque they use while I was at it?" Answer, "because I am a tunnel-visioned dolt."

Richard L.

[groily]

Absolutely NOT saying what torque should be applied Richard! Just that I tend to do 3/8th BSF fasteners to 34-35, perhaps out of fear of having more barrel threads strip on my particular A and perhaps because I spend a fair amount of time playing with more fragile things from earlier times. Happily it has worked perfectly for me since, during which time the machine has needed almost no attention despite a lot of use. Dare I say, it's as reliable as a modern? There are loads of people using 40 ft lbs I know, and it's obviously quite OK. I have a sort of suspicion that one reason for using the smaller heads on the bolts - apart from the physical space issue - was to discourage over-tightening, given the size of the wrench, pre-socket era, that could be applied. When I had my first A, I only had box spanners - the tubular things - and I challenge anyone to do anything up really well with them. But I really have no idea, I just follow instinct, likely wrong!, when it comes to not breaking things. Perhaps also comes from being a bit too large and having a tendency, painfully acquired, not to apply that final tweak which results in disaster!

[RichardL]

Oh, we're so far astray from the orginal topic no one will ever find us.

I just went and looked at some standard torque charts and found that 3/8" SAE Grade 8 steel bolts (leaving out some details like TPI) cound be torqued up to around 45 ft. lb. dry and 35 lubricated. This makes me glad I thought about this before hand and cleaned the oil off the bolts with some white spirits then dried them. Nevertheless, I'd bet there was some residual oil in the holes, meaning I am probabaly torqued-up too tight on some. The object is riding, right?

Richard L