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Cracked Blocks
#11
(14-10-2018, 02:33 PM)Zetomagneto Wrote:
(13-10-2018, 05:45 PM)Chris KC Wrote: Apologies if covered before, but many cylinder blocks now have small cracks radiating out from the centre head stud. The general consensus seems to be use another one if you have the choice.

I'm curious, has anyone actually suffered an engine failure as a result of these cracks?
And if yes, what happened? (Water in the bore? Stud pulled out? Or something more dramatic...?)

Anyone found a way to repair them?

Thanks
Chris

I believe these to be heat cracks.If the threads are in good condition just use as is, if the tread is iffy
go to 3/8 BSF and use a stepped stud which gives a much better result than helicoils, Attached are images of 2 blocks with this problem, it is not uncommon.If it was my block I would have the top face skimmed, drill out the water holes to clear them of crud/limescale,remove the coreplugs, and have ii
acid cleaned, or do it yourself with Bilthamber.I would not attempt to have this repaired, it will do more harm than good because there is so little material in the vicinity.
Someone mentioned oil coming up through through the studhole, strange as there is no oil there, the stud goes into the waterways.When refitting the studs I use loctite 242 to seal the threads.
I short Chris I wouldn’t worry about the crack.
Thank you Zete. I would have been interested to see your pics but I don't find them?
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#12
Do the cracks come with the relltively modern use of torsion wrenches and socket wrenches whereas in the distant past most owners just used standard length ring spanners?
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#13
Don’t think so Bob. I’ve got blocks that haven’t been used in donkeys years that still have the crack. Actually as long as it’s not running into a combustion chamber I don’t worry too much about them.
Alan Fairless
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#14
Torque wenches are more likely to prevent than create cracks, most damage done to sevens over the years seems to me to be the result of tools, and often the wrong one, in unskilled hands. At least a torque wrench removes the vagaries of strength and perceived tightness.
Black Art Enthusiast 
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#15
(14-10-2018, 04:57 PM)8Chris KC Wrote:
(14-10-2018, 02:33 PM)Zetomagneto Wrote:
(13-10-2018, 05:45 PM)Chris KC Wrote: Apologies if covered before, but many cylinder blocks now have small cracks radiating out from the centre head stud. The general consensus seems to be use another one if you have the choice.

I'm curious, has anyone actually suffered an engine failure as a result of these cracks?
And if yes, what happened? (Water in the bore? Stud pulled out? Or something more dramatic...?)

Anyone found a way to repair them?

Thanks
Chris

I believe these to be heat cracks.If the threads are in good condition just use as is, if the tread is iffy
go to 3/8 BSF and use a stepped stud which gives a much better result than helicoils, Attached are images of 2 blocks with this problem, it is not uncommon.If it was my block I would have the top face skimmed, drill out the water holes to clear them of crud/limescale,remove the coreplugs, and have ii
acid cleaned, or do it yourself with Bilthamber.I would not attempt to have this repaired, it will do more harm than good because there is so little material in the vicinity.
Someone mentioned oil coming up through through the studhole, strange as there is no oil there, the stud goes into the waterways.When refitting the studs I use loctite 242 to seal the threads.
I short Chris I wouldn’t worry about the crack.
Thank you Zete. I would have been interested to see your pics but I don't find them?
Have tried several times without success to upload them
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#16
(14-10-2018, 08:44 PM)Zetomagneto Wrote: Have tried several times without success to upload them

Based on Ruairidh's comment in another thread it sounds like there is a temporary system issue
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#17
I have used a block which has had the crack for 15 years.

This block was bored to 80 thou oversize in the 1980's , I only stopped using it when the cylinder walls got so worn I could stuff a 25 thou feeler past to piston.
This engine was thrashed up to 6000 RPM and did the 1997 JOGLE and did a few Hillclimbs
The block got changed two years ago for a better one.
I used to go through head gaskets a bit more frequently, I ended up using gasket goo to sort the problem the centre stud was also helicoiled and goo for good measure.
As long as the top of the block is flat just use some gasket goo and carry a spare head gasket and water.

When you find a better block get it bored new pistons, valve guides replace all the studs and you will be good to go for years.
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