Author Topic: Well, that didnt last long!  (Read 6437 times)

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Offline KiwiJohn

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Well, that didnt last long!
« on: 10 Dec 2005 at 07:46 »
I finally got my 80 Plus to run reasonably well, even got it legal for the road but after less than 50 miles a head gasket has blown. :cry:

Fortunately I have a used gasket that might be good enough to use again but is there anything I can do to it before putting it in?  It looks like a steel sandwich type.

Also, how the heck is one supposed to get the head nuts tight when no spanner known to man can be put on the nuts?

Offline Daren W Australia

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Re: Well, that didnt last long!
« Reply #1 on: 10 Dec 2005 at 07:52 »
Hi John had the same trouble last weekend assembling a T35 engine some of my heads have BSF threads and some have Admiralty Fine. What torque did you use the wrist clicking or your elbow click ?????? Daren PS your gearbox has been sent
too many dougli not enough time!

Offline KiwiJohn

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Re: Well, that didnt last long!
« Reply #2 on: 10 Dec 2005 at 08:07 »
Daren, I wasnt the one who assembled it and I note the nuts are not round shouldered at all but no spanner in my tool box will fit on the nut and not foul the fins so I am wondering what the trick is?  I suppose I could measure the nut and buy a spanner or two that I can offer up to the god of the angle grinder, it just doesnt seem right to grind bits off a spanner that has been in the family for a couple of generations,  OK to do it to a new one I suppose.

What would the recommend torque be? The only torque wrench I have is for a socket drive and I cant really see that getting in!  An estimate for the elbow could be useful.

Re gbox,  so I can expect to see a postie puffing up the hill later in the week!  thanks.

Offline Doug

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Re: Well, that didnt last long!
« Reply #3 on: 11 Dec 2005 at 00:27 »
I had to grind an open end spanner to do the ones up on my Mark 3.  I also blew out a head gasket, a replacement pasteboard affair (no metal) being sold at the time by LDMCC Spares, the sizable chunk of which struck me in the shin and surprised me no end.  Another with more torque lasted a bit longer (and they tend to settle with thermal cycling, which was my oversight on the first gasket) but it too blew.  Then I just sawed out some solid aluminum sheet stock and they have been in there ever since.  As for torque, well you are not going to get a proper torque wrench applied to such a restricted location.  Seems to me I used the highly scientific calibration of as much as I could pull without inflicting serious discomfort on a six inch long spanner.  Of course very uniformly applied to all the nuts!  That was ten seasons ago or so. 

-Doug
« Last Edit: 13 Dec 2005 at 03:45 by Doug »

Offline KiwiJohn

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Re: Well, that didnt last long!
« Reply #4 on: 11 Dec 2005 at 03:25 »
Thanks Doug, yes this was a LDMCC club spare too but it had only been through about two 'thermal cycles'!  I have heard that the spigot on the barrel may stop the head fully torqueing down on a too thin gasket.  I will be checking that.

Taking another look at the one that came out I see it is actually solid aluminium,  is that better, worse or the same as copper?

Offline Doug

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Re: Well, that didnt last long!
« Reply #5 on: 12 Dec 2005 at 01:57 »
John,

I think there is not much difference 'performance-wise' between solid copper or solid aluminum.  Both have near enough the same thermal properties and hardness that I do not think it much matters.  Obviously copper does have some advantage, else commercial head gaskets would not have used copper for years, but then they use steel now, so there is nothing sacred about copper.  Making them from sheet aluminum has the advantage that the material is more readily available and cheaper than copper.  In a wet environment, the aluminum might promote corrosion via a galvanitic reaction with the cast iron, but you do not leave your bike out in the rain, do you?  I lightly greased the surfaces of the heads and barrels on mine, just in case it had a mind to 'stick.' 

-Doug

Offline alwyn

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Re: Well, that didnt last long!
« Reply #6 on: 12 Dec 2005 at 09:19 »
Hi John, Doug and all,
Very early in the post-restoration life of my T35 a head gasket ruptured. On stripping the head I found the gasket was a composite copper sandwich, two faces of light gauge copper with a non-combustible fibrous (asbestos?) filler between - not questioning whether that type of gasket was OEM or not, I had a pair of similar gaskets made, one for each head. I must have done something right in cutting the template as they fitted perfectly and have given A1 service over about 6000 kilometres of travel. I check the head bolt tension when I think of it, tensioning only with elbow click and agree they a cussed thing to access. Now that the subject has been raised I have resolved to give the bolts a bit of a tweak, just in case!
Alwyn
« Last Edit: 12 Dec 2005 at 09:23 by alwyn »
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