johnm
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Because the coefficient of static friction is greater than the coefficient of dynamic or kinetic friction.
Get out your high school physics book for a bit of revision. ;-)
Cylinder Head Still Leaking
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Get out your high school physics book for a bit of revision. ;-)
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Thanks I was wandering about that myself.
Fast Eddie
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Fasteners seize / bind. You’re not interested in the torque measurement of the seizure grip, you’re interested in measuring torque of the clamping forces at the gasket joint.
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cliffa
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Ahhh, gotcha thanks. Makes sense now. So how far do you back them off?
cliffa
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Just to clarify Jim, I'm only talking about a really thin smear, not a 1/4" bead.
Fast Eddie
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Just till they ‘crack’.
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I appreciate this will sound very low tech but to trace an elusive oil leak just liberally apply talcum powder everywhere in the vicinity .
I did have an oil leak /head gasket issue with my ES2 for years and years. I had always torqued the 4 long bolts down to 25ft lb which seems quite enough but was told in fact it should be 35ftlb.. Steel bolts into alloy cases? seemed like a sure fire route to a helicoil job. So i compromised on 30ft lbs and that did the trick.. the engine holds compression as well as its oil and goes like stink. 90mph +on an Es2 is going like stink
Astonishing difference that 5ftlb made, but I wonder how many of us have torque wrenchesthat are accurate to with in such a small margin
I did have an oil leak /head gasket issue with my ES2 for years and years. I had always torqued the 4 long bolts down to 25ft lb which seems quite enough but was told in fact it should be 35ftlb.. Steel bolts into alloy cases? seemed like a sure fire route to a helicoil job. So i compromised on 30ft lbs and that did the trick.. the engine holds compression as well as its oil and goes like stink. 90mph +on an Es2 is going like stink
Astonishing difference that 5ftlb made, but I wonder how many of us have torque wrenchesthat are accurate to with in such a small margin
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Fast Eddie
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One at a time, in the correct tightening sequence.
texasSlick
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When re-torquing, I always approach torque spec by first adding torque until I reach spec.
CASE 1)
The fastener does not move. I crack it and bring it up to spec. In this case, cracking assures me that the fastener was not "stuck", and thus failed to move.
CASE 2)
The fastener moves before I reach spec. In this case, I know it was loose. If I had cracked it first, I would not know it was loose first.
If the fastener moves before reaching torque spec, bring it up to spec, then if you are crack happy, crack it and torque again, but IMO, the end result clamp force is the same either way.
For the first torque down, I go thru the torque pattern bringing each fastener up to some torque value well below spec. Then torque the pattern again to some value midway to spec, and finally torque again to 100% spec. One can break this procedure down to as many interim steps as one feels necessary or beneficial.
Slick
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Thanks Eddie, that's what I thought.
My head gasket is leaking slightly as I can see small bubbles at the edge of the gasket when the engine is running.
Please no advice on other likely causes. It is very obvioulsy leaking at the head gasket. Thanks
IIRC I intalled a composite head gasket 20+ years ago
The head bolts were installed and re-torqued several times 20+ years and 1000s miles ago
It is likely I did not grease/lubricate the bolts and nuts at that time.
Having read Norman's bible, I am thinking to removing the 5 bolts into the barrels and lubricating them
one at a time and in the correct order.
My thinking is that the bolts into cast iron are likely to be more "seized" than the nuts on studs.
All were brand new 20 + years ago.
I prefer to try to try to "nip it up" rather than replace the head gasket as as we all know taking an old
head off will lead to ...new valves, guides, spring, exhaust thread..... and maybe need to take barrels off
to find more issues. I prefer to spend the time working on another Norton then do the Commando later.
Thanks for any opinions
My head gasket is leaking slightly as I can see small bubbles at the edge of the gasket when the engine is running.
Please no advice on other likely causes. It is very obvioulsy leaking at the head gasket. Thanks
IIRC I intalled a composite head gasket 20+ years ago
The head bolts were installed and re-torqued several times 20+ years and 1000s miles ago
It is likely I did not grease/lubricate the bolts and nuts at that time.
Having read Norman's bible, I am thinking to removing the 5 bolts into the barrels and lubricating them
one at a time and in the correct order.
My thinking is that the bolts into cast iron are likely to be more "seized" than the nuts on studs.
All were brand new 20 + years ago.
I prefer to try to try to "nip it up" rather than replace the head gasket as as we all know taking an old
head off will lead to ...new valves, guides, spring, exhaust thread..... and maybe need to take barrels off
to find more issues. I prefer to spend the time working on another Norton then do the Commando later.
Thanks for any opinions
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- 696
For what its worth:
equal torque of the bolts does not mean equal pressure on the head gasket.
Ideally, all bolts should have the same length, and the area on which the pressure is applied should be equal for each bolt.
If you look at an 850 gasket, this is not the case.
When torquing the bolts to specs, you are already warping the head.
You can ( IMO should..) remove the rear lobes of the gasket, so that it looks more like a 750 gasket.
Narrower surface = increased specific pressure and better cooling.
A modified 850 gasket over a (chalked) std .
Seals better, cools better:
You can use 5 same length top head bolts with an alu spacer for bolt 1
Use longer studs and helicoil the threads in the head, or use an insert.
Place spacers on top of the trough bolts.
If I where to make a cylinder barrel ( but I can't) like G81 , I would remove the marked area:
IMO, the gasket surface is too unequal and too wide.
equal torque of the bolts does not mean equal pressure on the head gasket.
Ideally, all bolts should have the same length, and the area on which the pressure is applied should be equal for each bolt.
If you look at an 850 gasket, this is not the case.
When torquing the bolts to specs, you are already warping the head.
You can ( IMO should..) remove the rear lobes of the gasket, so that it looks more like a 750 gasket.
Narrower surface = increased specific pressure and better cooling.
A modified 850 gasket over a (chalked) std .
Seals better, cools better:
You can use 5 same length top head bolts with an alu spacer for bolt 1
Use longer studs and helicoil the threads in the head, or use an insert.
Place spacers on top of the trough bolts.
If I where to make a cylinder barrel ( but I can't) like G81 , I would remove the marked area:
IMO, the gasket surface is too unequal and too wide.
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