Combustion area - hairline crack

[campbellju]

Just visited the engine builder.

The head I got has pressure tested okay and the cams rotate cleanly. He sorted out an issue with the head studs and when cleaning in the port area found this small hairline crack in the combustion area on 2 cylinders. Both are small and no signs of det so the rest of the combustion chambers looks clean. He said most of the engines he repairs probably have this but you can't see the crack for the coke deposits on top. However, he suggested it's better to check with people more familiar with the head in case this is an early sign of failure rather than a small stress relief crack.

 

[STU666V]

I have a head in the garage with a crack in the same place. Not sure if its ok or not?
Might be a big paper weight?

 

[PobodY]

Is it repairable; weld over the top and grind back?

I don't know, but I suspect the builder is right and it's one of those things you only see if you look for it. :shock:

 

[campbellju]

It is repairable but another second hand head would be significantly less. You would need to clean the head to find out if it's got the same issue or not. He said it's probably more common than people think but on a 40hp per cylinder engine it might be less of a big deal than a 100hp per cylinder.

I'm sure my last head had the same problem but this nearly 10 years ago so I struggle to recall and it wasn't the cause of engine failure anyway.

 

[PobodY]

...and now that you know it's there, it's going to niggle at you if you use it. :lol:

 

[red reading]

It's not good practice to use a head like that as there is a minute chance the seat could move, I have actually taken a die grinder to one before to see and there is a huge amount of metal there before it would reach any water way.

i have also seen these sr20 with numerous cracks in the heads make silly power and last......

 

[campbellju]

Thanks Danny

I went into Nissan to pick up the gasket set. I know them well there and showed them the head as it was in the boot. They were cautious to say the least about re-using the head. Reading around the interweb these sort of cracks are common on heads but failures of the valve seat less so.

Given my luck recently I'm going to take this slowly

 

[Thor]

Hi James!

one crack is nothing! I had few years ago as we mapped mine car 8 cracks and the dyno result was 515 PS ;-)

That is the answer why i could run so much boost i think.

It is repairable but i had heard that it is not so good! Most people had problems after welding because it cracks adjacent to the weld position!

Regards
Sascha

 

[vpulsar]

Just get another head then you don't have to worry about it, Can you still buy new heads ?.



Rob

 

[campbellju]

Thanks Sascha and Rob for your advice. I'm not rushing this issue as my bottom end is still needing to be built. A new head from Nissan will be too expensive so I'll see what comes up 2nd hand. I'm not going to get this head ported as I might be throwing good money after bad. At worst I might fit it and it'll probably be fine but as George says I'll always wonder if the valve seat is going to drop. More likely to become another garage paperweight.

P.S. Sascha, its been a long time! I hope you and the family are well.