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Re: Head Gasket Impression in Head [Re: perfect.tommy] #759211 12/13/18 10:23 pm
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Perfect Tommy, go back and read post # #759161, the last sentence...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
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Re: Head Gasket Impression in Head [Re: perfect.tommy] #759224 12/14/18 12:14 am
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I always reckon that if your bike isn't leaving an oil stain on the concrete its one of two things:

1. Time to check your oil level, or

2. You have a damn good bike.

I strive for the latter, and just ride them. If I was doing something like speed trials or some such I guess I would question small imperfections or anomalies - in the pursuit of speed or a win - but mine are just road bikes so as long as its going, not dripping oil everywhere, and tuned right I'm happy.

Tommy one other thing that would be worth asking is was the gasket checked for uniformity [thickness] prior to installation? Something we all rarely do. And if the gasket was pre annealed - and you didn't anneal it yourself - is it possible that the centre hole was used to hang it and so wasn't annealed to the same consistency as the rest of the gasket [ie was harder] and this caused the issue? I realise that copper in any form is likely softer than alloy, but even so alloy would yield under a torque wrench, as the copper itself would have, but just not as much as the rest of the gasket. Long shots, but for strange outcomes.

Re: Head Gasket Impression in Head [Re: perfect.tommy] #759232 12/14/18 2:28 am
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Hi Tommy, Find your observations most interesting.

I just measured used '69 Bonnie head gasket. Known history, genuine Triumph copper gasket. The thickness varies between .0452 to .0463" The thinner is along outside edges. The center bolt area is quite even from front to back with no dips at all. I measured with a micrometer at several places. With a straight edge the gasket is on perfectly flat. It has a slight twist & bow. About .005". Of course this could skew micrometer reading slightly as well.

My straight edge is rated at .0002" per foot. On my lathe ways it rocks with a .0005 blade under it so it seems quite flat.

Block showed flat within .0005. Straight edge pinched .0005" feeler blade. Head .0005 blade was a snug slip fit. .001" blade was pinched full tight. I'll call the warp .0005" on head. It was low on the outer edges. I found no dips or humps. The .0005 was a slight bow.

Point is on this motor I see no dip or humps in old gasket. I used Mercedes sealant on head gasket during assembly of this motor. The gasket area has remained bone dry for about 3 k miles so far.


My TR7Rv head & block both tested within .0005". Pinching feeler tight. Also used Mercedes sealant. Has remained dry for 6k miles so far.

I have measured pinch or should I say how much gaskets squeeze down on a handful of copper gaskets now. Overall I find they squish by only about .0012". Some times thinner near edges.

I had a small stock pile of genuine copper head gaskets from 70s. I find they measure flat within about .0002", Measuring copper gaskets from Rabers they measure the same variation. So quite close to flat. I find the thickness overall has some variation from about .041" to .055". These are considered standard thickness. Oversize are available in .070 & .120" for 650. I've only seen .070" for 750 twin. I've used oversized to the exact same results as normal thickness. The compression of oversize seems very similar. Just over .001 so the extra thickness doesn't seem to change that. The oversize do not seem to migrate out or loose torque any different than normal.

My experience has been bow doesn't seem to make gasket leak, but dips between bolts has been at least prone to leaking what looks like oil from combustion area. There is no oil around the area so it has to be from combustion gasses. I find dips more than .0015 tended to result in actual blown gasket. This has been across cylinders, not to outside.

I have always skimmed heads I felt were not flat enough. I didn't know about straightening until 5 years ago. All the heads that I've worked on that blew gasket had low spot between cyl. I do not believe this could be straightened to flat enough tolerance.

Most of these heads had to have .007-.015" or so removed to get flat surface. Morgan Machine & Marine Walnut Creek, CA did work. Specifically Tim Morgan did it personally. The machine had a very large cutter head with multiple tool bits so entire gasket surface could be cut in one pass. Usually took 2-3 passes to clean up. Tim was most careful to mount head to keep from tilting rocker box surface & remove least metal as possible. All these had 100% success. Back in the 70s & 80s I used K&W copper coat on gasket. To be clear, every head that was marginal even with K&W seeped oil from head gasket. All the surfaced ones did not leak. The ones that needed surfacing, but didn't get it blew head gasket again within 3k miles or sooner.

I find in most interesting that many have good results with heads that measure much worse than mine.

Tommy, exactly how are you measuring thickness of head gasket?

Seems odd you gasket would measure this way with both sealing surfaces flat.

Don


1973 Tiger 750
Re: Head Gasket Impression in Head [Re: perfect.tommy] #759242 12/14/18 6:26 am
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Interesting diecussion, would also love to see a picture of the depression.


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Bikes: '69 T120 on average (1967 rolling frame and 1971 Bonnie engine) + '56 1/2 T110 on average (58 rolling frame - with 55 iron head engine)
Re: Head Gasket Impression in Head [Re: perfect.tommy] #759250 12/14/18 12:02 pm
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Without a photo this conversation is a bit useless.....Aftermarket manufacturers of copper gaskets for performance engines say copper gaskets will conform to small imperfections but will not compress...I have have the head off my Triumph 650 race bike about 5 times.The same gasket is used, annealed each time..The gasket still measure .041" like it did the first time...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Head Gasket Impression in Head [Re: perfect.tommy] #759254 12/14/18 12:40 pm
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A bit of silk soaked positioned around potential leak points near the depression would be a good fix. Works on Commando heads to protect the push rod tunnels.

[Linked Image]


Re: Head Gasket Impression in Head [Re: kommando] #759272 12/14/18 2:18 pm
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Is that just ordinary silk thread? Soaked in water?


If anything other than a blank space is visible here, something's wrong.
Re: Head Gasket Impression in Head [Re: perfect.tommy] #759287 12/14/18 4:31 pm
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Ordinary silk thread, you can put some coppercoat or some sealant on it. It goes on both sides of the gasket.

Re: Head Gasket Impression in Head [Re: perfect.tommy] #759290 12/14/18 4:50 pm
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I'm envious that Nortons have flat top pistons...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Head Gasket Impression in Head [Re: kommando] #759306 12/14/18 7:15 pm
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Great tip - I'm sure it will come in useful on non-Norton applications. I have pondered whether something like this might work but never known what material would be suitable. Long ago, boatbuilders would use single horse-tail hairs to seal between planks. Similar kind of principle.

Can I check about the "soaked" bit? Did you mean the silk thread should be soaked in something prior to this? or was that a typo? Thanks.


If anything other than a blank space is visible here, something's wrong.
Re: Head Gasket Impression in Head [Re: perfect.tommy] #759317 12/14/18 8:54 pm
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Kom - intriguing! What's the principle at play here? Is silk critical, or can cotton do? Is it still there when you next take the head off, or just charcoal? I wonder if fine wire may do it?

Re: Head Gasket Impression in Head [Re: HawaiianTiger] #759324 12/14/18 9:25 pm
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Bill, this information is great and I think this is getting to the heart of the issue.

If we go back a few years, I had real problems getting the head gasket to seal. There were a platitude of reasons for this at the time; pushrod tube crush height and non-anealed gaskets being some of them. The one that alluded me for some time dealt with torque settings. An early mentor of mine had ingrained in me that fasteners were never to be used without lubricant. The problem here is that torque values in the Triumph workshop manual are only given dry. So I was using a conversion factor to estimate the reduction in torque when using moly. What became clear, especially after I had a conversation with ARP about their fastener lubricant, is that my calculations were at best, a guess.

On those early assemblies with blown gaskets we saw impressions in the head and gasket material running the length between cylinders. It seems more clear now that my guesstimated torque values were far over, not under, and the fasteners were tightened beyond their ability to continue to stretch.

If we look at modern head bolts, they have a "waistline" to allow for this kind of stretch during thermal expansion. Keith and Harold at Johnson Cam's modify their stock head bolts by turning down the mid-section on a lathe. Jim Schmidt in the Norton world provides tapered head bolts as well. These bolts, when not overtightened, have some elasticity.

While the last few assemblies have stayed sealed (since assembling dry with stock recommended torque values) I think it may be worth installing a brand new centre head bolt. And even though my torque wrench is made by Snap-On and came with a certificate of calibration it might be worth while getting it tested for accuracy.

I think it is lack of bolt stretch in this very hot area of the motor. Bill, I really appreciate you sharing this.



1970 Triumph Tiger
Re: Head Gasket Impression in Head [Re: koan58] #759327 12/14/18 9:27 pm
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I think thin copper wire .005" thick is more common in the Norton world. Check Jim Schmidt's website for details.


1970 Triumph Tiger
Re: Head Gasket Impression in Head [Re: NickL] #759328 12/14/18 9:29 pm
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[quote=NickL]The easiest way is to change your name to 'imperfect Tommy' /quote]


I like it.


1970 Triumph Tiger
Re: Head Gasket Impression in Head [Re: perfect.tommy] #759331 12/14/18 10:25 pm
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With regard to the silk thread method, it is routinely specified by aircraft engine manufacturers as an aid in sealing surfaces without gaskets. A thin film of sealant and the correct material thread is specified.

I would think that it would be something problematic that might drive you to try this technique. After all we have anaerobic sealants, Covseal gaskets and a few other proven techniques for our old bikes.

The weeping push rod tunnels on Commandos just might quality. I rode mine around for years with a weeping head gasket and just washed my bike weekly. Eventually I found and bought another head that solved my problem.

Cheers,
Bill



Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Black Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
Re: Head Gasket Impression in Head [Re: TR7RVMan] #759332 12/14/18 10:31 pm
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Don, great post. And finally, someone who measures in tenths!

Believe it or not, I have never measured my head gaskets for uniformity, though I seem to measure everything else. MAP's gaskets have definitely been the softest I have used, and anyone who has purchased parts from Marino can attest to their level of quality and precision. Tim Joyce's (5 year?) run as champion on an Triumph built with MAP components is certainly a testament to that as well. But now you have me curious...

Yes, my blown head gaskets have always been between cylinders too.

I think Bill from Hawaii is on to my issue. Wrong torque or unyielding bolt in an area that sees a lot of thermal expansion. While my last assemblies have stayed air tight, it would be nice to see an un-uindented gasket surface after disassembly. I think we are close now.


1970 Triumph Tiger
Re: Head Gasket Impression in Head [Re: TR7RVMan] #759354 12/15/18 1:02 am
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Originally Posted by TR7RVMan
Hi Tommy, Find your observations most interesting.

I just measured used '69 Bonnie head gasket. Known history, genuine Triumph copper gasket. The thickness varies between .0452 to .0463" The thinner is along outside edges. The center bolt area is quite even from front to back with no dips at all. I measured with a micrometer at several places. With a straight edge the gasket is on perfectly flat. It has a slight twist & bow. About .005". Of course this could skew micrometer reading slightly as well.

My straight edge is rated at .0002" per foot. On my lathe ways it rocks with a .0005 blade under it so it seems quite flat.

Block showed flat within .0005. Straight edge pinched .0005" feeler blade. Head .0005 blade was a snug slip fit. .001" blade was pinched full tight. I'll call the warp .0005" on head. It was low on the outer edges. I found no dips or humps. The .0005 was a slight bow.

Point is on this motor I see no dip or humps in old gasket. I used Mercedes sealant on head gasket during assembly of this motor. The gasket area has remained bone dry for about 3 k miles so far.


My TR7Rv head & block both tested within .0005". Pinching feeler tight. Also used Mercedes sealant. Has remained dry for 6k miles so far.

I have measured pinch or should I say how much gaskets squeeze down on a handful of copper gaskets now. Overall I find they squish by only about .0012". Some times thinner near edges.

I had a small stock pile of genuine copper head gaskets from 70s. I find they measure flat within about .0002", Measuring copper gaskets from Rabers they measure the same variation. So quite close to flat. I find the thickness overall has some variation from about .041" to .055". These are considered standard thickness. Oversize are available in .070 & .120" for 650. I've only seen .070" for 750 twin. I've used oversized to the exact same results as normal thickness. The compression of oversize seems very similar. Just over .001 so the extra thickness doesn't seem to change that. The oversize do not seem to migrate out or loose torque any different than normal.

My experience has been bow doesn't seem to make gasket leak, but dips between bolts has been at least prone to leaking what looks like oil from combustion area. There is no oil around the area so it has to be from combustion gasses. I find dips more than .0015 tended to result in actual blown gasket. This has been across cylinders, not to outside.




I have always skimmed heads I felt were not flat enough. I didn't know about straightening until 5 years ago. All the heads that I've worked on that blew gasket had low spot between cyl. I do not believe this could be straightened to flat enough tolerance.

Most of these heads had to have .007-.015" or so removed to get flat surface. Morgan Machine & Marine Walnut Creek, CA did work. Specifically Tim Morgan did it personally. The machine had a very large cutter head with multiple tool bits so entire gasket surface could be cut in one pass. Usually took 2-3 passes to clean up. Tim was most careful to mount head to keep from tilting rocker box surface & remove least metal as possible. All these had 100% success. Back in the 70s & 80s I used K&W copper coat on gasket. To be clear, every head that was marginal even with K&W seeped oil from head gasket. All the surfaced ones did not leak. The ones that needed surfacing, but didn't get it blew head gasket again within 3k miles or sooner.

I find in most interesting that many have good results with heads that measure much worse than mine.

Tommy, exactly how are you measuring thickness of head gasket?

Seems odd you gasket would measure this way with both sealing surfaces flat.

Don


Top work, well measured and written.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: Head Gasket Impression in Head [Re: Hillbilly bike] #759393 12/15/18 12:53 pm
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Originally Posted by Hillbilly bike
I'm envious that Nortons have flat top pistons...


+1


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
Re: Head Gasket Impression in Head [Re: perfect.tommy] #759399 12/15/18 2:34 pm
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Lots of talk of precision measuring on engines that when running under heavy load are anything but true and straight grin In my opinion, many problems on Triumphs including funny head gasket business is caused by detonation. Many of you think if you hear the slightest ping the pistons will seize or fall into the sump..While that can happen if the rider just keeps it up...., what also can happen is the piston doesn't always fail and repeated mild detonation at high power levels can beat up on engine parts.It can cause barrels and heads to fret on the joints causing oil leaks . Like what Bill Hawaiian Tiger said. Detonation can crack cranks and ruin bearings..It's not easy to hear detonation at higher speeds , the rider may or may not feel it...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Head Gasket Impression in Head [Re: Hillbilly bike] #759412 12/15/18 7:36 pm
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I think you are confused about what is going on here. There has been no evidence provided to support a case, or cause, for detonation in this thread.

And if you are suggestion that precision measuring when building engines is a waste of time... you might want to think again.


1970 Triumph Tiger
Re: Head Gasket Impression in Head [Re: perfect.tommy] #759415 12/15/18 8:11 pm
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Originally Posted by perfect.tommy
I think you are confused about what is going on here. There has been no evidence provided to support a case, or cause, for detonation in this thread.

And if you are suggestion that precision measuring when building engines is a waste of time... you might want to think again.


I'm just talking in general, not necessarily about your engine, ....... Do you use a torque plate when boring/honing the cylinders? Do you make sure the cylinders are bored at 90 degrees to the crankshaft? Do you make sure the crank main bearing bores are exactly the same? Do you check the cam timing with a degree wheel? Do you have valve jobs done on a single axis machine? What valve/guide clearances do you use? Do you assembly the rods with bearings and have a crank turned to the actual measurement rather than what's printed in the manual? Are the crank throws checked for clocking?.. Does your bike have an oil pressure gauge or you trust a precision engine to a indicator light?
A head can be checked with a straight edge or it can be placed rocker side down on ground flat table and checked with a dial indicators so you'll know if both surfaces are parallel...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Head Gasket Impression in Head [Re: perfect.tommy] #759417 12/15/18 8:30 pm
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Detonation.... In California, holed & destroyed pistons are extremely common. A very serious issue. I don't know all the related damage done to motors, but I've seen several heads where it looks like an object bounced around in combustion chamber leaving pock marks on head & piston.


However no know objects got into motor. The motor appears to have been working fine all along. Ping could be heard during heavy loading in each case. Remember ping is happening before you can hear it. I really can't tell difference between detonation & ping when I hear it.

I've ridden several machines where owners say they never hear any ping. I hear ping when I road test under load. 2 of these owners have holed pistons. One more than once. This is a serious matter that results in very costly repairs.

I've been building motors for over 40 years. Precision machining & build quality are everything. Poor tolerances & assembly assure a short motor life. See this all the time on the club rides. The well assembled motors do fine. The poor assembly often ends up in chase truck. Just the laws of physics. Sadly the factory tended to error on the side of just ok was good enough.

Interesting subject.
Don


1973 Tiger 750
Re: Head Gasket Impression in Head [Re: perfect.tommy] #759418 12/15/18 8:31 pm
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Hi Tommy, So what is your gasket measuring with the micrometer? You didn't answer that.
Don


1973 Tiger 750
Re: Head Gasket Impression in Head [Re: TR7RVMan] #759452 12/16/18 12:13 pm
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Originally Posted by TR7RVMan
Detonation.... In California, holed & destroyed pistons are extremely common. A very serious issue. I don't know all the related damage done to motors, but I've seen several heads where it looks like an object bounced around in combustion chamber leaving pock marks on head & piston.


However no know objects got into motor. The motor appears to have been working fine all along. Ping could be heard during heavy loading in each case. Remember ping is happening before you can hear it. I really can't tell difference between detonation & ping when I hear it.

I've ridden several machines where owners say they never hear any ping. I hear ping when I road test under load. 2 of these owners have holed pistons. One more than once. This is a serious matter that results in very costly repairs.

Interesting subject.
Don



79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Head Gasket Impression in Head [Re: TR7RVMan] #759455 12/16/18 12:36 pm
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Originally Posted by TR7RVMan
Detonation.... In California, holed & destroyed pistons are extremely common. A very serious issue. I don't know all the related damage done to motors, but I've seen several heads where it looks like an object bounced around in combustion chamber leaving pock marks on head & piston.


However no know objects got into motor. The motor appears to have been working fine all along. Ping could be heard during heavy loading in each case. Remember ping is happening before you can hear it. I really can't tell difference between detonation & ping when I hear it.

I've ridden several machines where owners say they never hear any ping. I hear ping when I road test under load. 2 of these owners have holed pistons. One more than once. This is a serious matter that results in very costly repairs.

I've been building motors for over 40 years. Precision machining & build quality are everything. Poor tolerances & assembly assure a short motor life. See this all the time on the club rides. The well assembled motors do fine. The poor assembly often ends up in chase truck. Just the laws of physics. Sadly the factory tended to error on the side of just ok was good enough.

Interesting subject.
Don



By holed pistons if you mean a hole in the piston crown, that's pre ignition not detonation.To distinct events with different causes....Detonation beats up on the circumference of the piston, can errode the piston crown, cracks rings and can heat the piston to seizure..
I was a construction electrician not a trained engine mechanic..I learned to work on vehicles because I always drove junk that needed repairing at times..I built a few bike and truck engines and they ran nice and didn't blow up so I figured I did it ok..Then I built the race bike and did some things that some here may consider, well, hillbilly .But it keep going faster and setting new speed records..Might not be stuff you want to do on a street engine but it can be surprising how long an engine built from a pile of parts on the floor can last if you keep it clean and use common sense..and if rebuilding an engine you took apart then the various pieces will have wear marks that can be clues to potential issues.
The OP on this tread has an engine that appears to have been checked over very carefully but it leaves a odd mark on the head ...I have to ask again, is it causing a problem and why has the OP pulled off the head more than once?



79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
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