Cracks in the head!!

I don't think it's so much of a repair, more of a sealer to stop the oil leaks. Combustion chamber is a whole different kettle of fish!!

Thanks Keith, that's what I'll do then, cheers.
 
How would something like J-B Weld or loctite epoxy weld go? We used to use J-B Weld to repair domestic freezer cabinets that folk had punctured while "cleaning" with a knife. Used to withstand high gas pressures ussed for testing the unit and survived for years with the gas pressure and cold of the freezer. Frommemory was rated to around 500F and wa resistant to oil and petrol.
 
Andy Wagners catelogue which you have to buy,  i.e not just the on-line parts lists, has quite a bit in with pics about this issue, I recall.
So who is going to knock up some new heads,eh, there are forever problems with the bloody things....
Nick7
 
Maybe once Red has the Dyno under control and the 20 odd bikes restored he will get round to knocking up a few 4-valve heads in his spare time...  (goodjob)
 
Totally fuck up the brawny charm of a two valve engine putting a four valve head on it, would also be a rather fruitless exersize in terms of development costs verses actual improvement gained due to the small piston area to long stroke architecture you won't get the best advantage of the four valve layout, would have to dramatically increase the bore size and reduce the stroke to get it to match power expectations and that just won't fit with what we got regarding crankcases also likely to need water cooling to cope with the extra heat all that four valve power generates and a plain bearing crank to cope with the high rpm...you just made a modern Triumph, so if you want to see what it would be like save a shit load of money and go try a modern
Triumph. They are fast powerfull and smooth but a bit effete and whizzy whizzy dull...which is why we ride old bikes, 'cos they are not they are brawny and rock hard.
  Now, if someone could cast up a load of RGS heads...

    Keith.
 
Rob,

Repaired dozens of those, very common.  I have them laser-welded, loads cleaner and far safer than conventional welding.  No danger of warping, takes about 20 minutes with a file and emery to get the weld fillets smoothed out afterwards.  No need for total surface machining, which fucks up all manner of clearances in and around the head/cam assembly.

Gijs' theory is the bracing across the cam chain tunnel exerts pressure to the opposite walls and thus cracking them over time.  At least the heads I have modded have not shown any further tendency to crack.

piet
 
Laverdalothar said:
laverdakeith said:
Now, if someone could cast up a load of RGS heads...

    Keith.
Click to expand...

You mean Corsa heads, right?  ;)
Click to expand...

The scrapyards are full of 3cyl Corsa heads how many do you want? :D

                                                                                          Dave
 
I fixed a cracked alloy sump on an auto mini years ago multiple hairline cracks) - I used cellulose thinners to clean the cracks of oil (in that case chemical metal worked well to stop the leaking as it could easily be applied from he outside face and moulded around the casting ribs).
 
Piet, unforunetly I live in Oz, we are still in the dark ages with some technology as I've never heard of lazer welding available here. Only lazers we have are mounted on the car dash or held in the hand of the local filth or some idiots shinning those lazer pointers at planes as they land!!

So, with out access to a lazer welder I've decide to go with keith's option of Loctite. The head is torqued down on the block so will leave it on there, stuff rags in the chain tunnel and give it a damn good squirt with brake cleaner. Heat it up with a hot air gun or propane torch and apply the loctite. I like Davo's idea of JB weld, could push some into the corners, might help with sealing the oil leaks. There is a slight step across the crack that should'nt be a problem with the cover gasket.

I think I should start looking for a spare head, anyone??

A mate in Perth has got one of those multi axis mills so maybe for a few cartons of piss he might knock out a new head for me in billet. Must give him a call!!
 
Given heating up would widen the cracks, could heating up to open the cracks before applying loctite potentially increase the chances of the cracks widening? I'm wondering whether as the metal cools the crack will not be able to shrink back to normal with the loctite now in place - although the metal around the crack would still try to shrink back adding stress to the crack area?

Along the same lines the new state of the crack when the head becomes cold would be as open as it would have previously been when hot. This becomes the new starting point so when the engine gets warm it will tend to open further from this cold point.

I think it's time for a lie down..
 
I don't know what the chemical make-up of Loctite is, but I presume it's some kind of polymer. Polymers generally have a higher coefficient of thermal expansion than aluminium, so my guess that filling a crack in a warm head will minimise any risk wedging it open on cooling because the filler will contract more than the aluminium.

Cheers,
Cam
 
Rob,

Apparently the Dark Ages of Engineering are present in all corners of the planet, not only in the back o'Bourke.  Quite often get blank stares over here when I mention this or that... :o

Tried JB-Weld myself many moons ago, lasted for a season or 2 before it started leaking again, probably too many heat cycles for it to handle.  Easy to replace though, oil had usually penetrated far enough to be able to peel the lump off in order to apply a new coating!

If that Loctite stuff can handle the heat over time, It may well be a fine "repair".

piet
 
motoddrob said:
Piet, unforunetly I live in Oz, we are still in the dark ages with some technology as I've never heard of lazer welding available here. Only lazers we have are mounted on the car dash or held in the hand of the local filth or some idiots shinning those lazer pointers at planes as they land!!

So, with out access to a lazer welder I've decide to go with keith's option of Loctite. The head is torqued down on the block so will leave it on there, stuff rags in the chain tunnel and give it a damn good squirt with brake cleaner. Heat it up with a hot air gun or propane torch and apply the loctite. I like Davo's idea of JB weld, could push some into the corners, might help with sealing the oil leaks. There is a slight step across the crack that should'nt be a problem with the cover gasket.

I think I should start looking for a spare head, anyone??

A mate in Perth has got one of those multi axis mills so maybe for a few cartons of piss he might knock out a new head for me in billet. Must give him a call!!
Click to expand...

Hi Rob,
I can't believe that there is no laser welding in Oz. Have a look here:
http://www.hotfrog.com.au/Products/Laser-Welding
Ciao, Gert
 
well - what are your choices basically?

a) unmount the head and get it fixed
b) leave it as is
c) try loctide

You could start with b), as it did not leak for 50.000+ kilometers, so why should it now? If it does, you could try c) and if that does not fix it for long, you could try a) still. Don't see any issue here.

The only point is that you will be having a weird feeling every kilometer you run the bike and will inspect it very often for oil leaks. But as you have to run-in the engine anyway, I would simply leave it as it is or for your peace of mind would try the loctide method (while not seeing really who you could get the thing deep enough into the crack to make a difference, but that's a different story.

So -basically two choices: live with the potential risk or decide for peace of mind and get it fixed. Up to you.  ;)
 
I'm going with the loctite option and some JB weld in the corners. It has been leaking Lothar, always wondered why the centre plug and HT lead were always oily.
As for lazer welding, I found one in Sydney and that hotfrog link shows one in Qld. From where I live they may as well be in timbukto!!
 
Rob, be careful about Internet searches for laser welding. It's also used for sticking together bits of medical grade plastic in manufacturing various types of therapeutic devices. I was quite excited to discover how many companies did "laser welding" near me 'cos I need my top crankcase welded after a chain let go sometime in the previous life of the bike. But when I started calling them, they all turned out to be medical plastic production only.

Ken
 
Just refitting the head after having a go at fixing the cracks using Loctite 290 as Keith suggested. Also, using a small round burr I ground out the crack going down the cam chain tunnel, about 15mm. I then fillled it with JB Weld. Hopefully this will solve the oil leaking issue.
 

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