Cracked Blocks

[Chris KC]

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

[Peter Clayton]

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

Had this on my block several years ago. The problem is one of head gasket failure as the stud when the engine gets hot no longer retains its torque thus water enters the bores and gases get blown into the coolant. As far as I can tel there is no cure . any helicoil would come loose like the stud and any attempt at welding the block would ,I suspect, cause  irrepairable  block distortion. Not sure if drillingthe block deeperand using a longer stud with some "plastic metal" would effect a temporary repair but somehow doubt it. Easier to get a replacement block.

[Chris KC]

Thanks for your thoughts Peter.
Yes in an ideal world I guess I'd look for a better block, in this particular instance though it's more a question that I have a nice block with only this issue and whether the crack should put me off using it.

[David Witton]

Chris I had this problem with oil oozing through the centre stud being the usual symptom. Against the advice of many who warned me against wasting my money, I had it repaired by Surelock Castings (no connection or vested interest).

Nearly 8 years later the car, ( a 32 RN), still starts on the button regardless of the previous idle period and will easily do 55 on the flat so I wouldnt necessarily throw the block away.

[Peter Clayton]

Chris I had this problem with oil oozing through the centre stud being the usual symptom. Against the advice of many who warned me against wasting my money, I had it repaired by Surelock Castings (no connection or vested interest).

Nearly 8 years later the car, ( a 32 RN),  still starts on the button regardless of the previous idle period and will easily do 55 on the flat so I wouldnt necessarily throw the block away.

David,do you know how the repair was achieved,was it cold stitched,or perhaps a plug inserted and redrilled/tapped ?

[David Witton]

Peter, from memory it wss stitched.

[Robert Foreman]

Stitching works very well, if the crack is small you could always use wicking Loctite which is also used for porous castings.

[Chris KC]

Thanks guys, some interesting thoughts there.

I confess I'm struggling a bit to picture how it would be stitched when it's such a narrow area, also perhaps depends which direction the crack(s) is heading. I know this method works on larger castings though so could be worth a phone call.

Loctite 290 sounds interesting. I note the data sheet says :

For Porosity Sealing
1. Clean area and apply localized heat to the area to approximately 121°C.
2. Allow to cool to approximately 85°C and apply the product.

It also has some claimed tolerance for contamination (no way you're getting in there to clean the surfaces).

Encouraging though that no-one yet has reported a block splitting in half...

[AustinWood]

I suspect that the root cause of these cracks is over tightening the head. The gasket compresses around the stud causing excess force on the stud.

[Zetomagneto]

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.