[FreedomFirst]

It is entirely possible to remove the seats, repair the crack, chase the plug hole and remill the pocket for the valve seat. IME they will crack again in time.

[pyrrhos]

My machine shop would NOT service any heads with these cracks. It took us quite a long time to find a set of EJ205 heads without these cracks. It is very common. However, once we finally found a set, they reinforced the areas where it's prone to crack so they would not crack in the future.

[jas143moe]

I spoke to the machine shop about it. They said they could last forever/or they could be fixed but we looked at the process together and it was time consuming.

[catherine99]

I'm having trouble trying to find a decent set of '99 wrx heads for my build. They seem OK until I have them chemically cleaned, then there are hairline cracks exposed between the spark plug entry and the valve seats.

[mshare1]

It is actually common in many air cooled motorcycle engines. Many shops don't even have an issue working on these, they will do a valve job , note it and give them back if you wish.

[Nefario]

My question is what issues have people found and at what sort of boost and hp levels?
Have people used heads like this on high hp builds without any issues?

[Iron47]

Someone had also dropped a screw/bolt into the engine at some previous time. Probably fell in through the spark plug hole. [links]

[jinnyh345]

This crack was enough for me to replace the head. Quite possibly the engine may have been running lean, overheated, burned the valve and cracked the exhaust port. I didn't ever get the head checked in any detail, but more than likely it may have also been warped. Either way, it went to the bin. [links]

[mycroftholmes]

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[Cab1945]

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[Ramapithecus]

[sunglasses]

The most common place for a crack is between the valve seat and cylinder. An old timer told me that you see more cracks on the intake side than the exhaust side because the metal is stressed by being alternately heated by combustion and cooled by the intake charge, but I don't know if it is true. Whether it is worth repairing these blocks depends on whether or not you can find both ends of the crack, how far it goes, and how many there are of them.

[Balcerek]

This is another view of the same cracks. more

[afed]

This is a bad repair job using plugs, I think. I don't see any threads where the block broke away as would be seen with a proper plug, and in real life, there is a bronzy cast to the repair making me wonder if brazing was used. I can't imagine that brazing wouldn't have melted away, but this engine had so many bad mechanic things in it, nothing would surprise me about it. I even found lead shot in the crank case.

[sizeddenim]

This is the most common crack point to afflict all models of MGB cylinder heads. Water leaking externally above the spark plug hole and water leaking into the rocker cover area are the problems most commonly associated with this one. We've never seen a repair in this area last, so heads like this are junk.

[michb]

The above image shows what not to do when trying to fix a cracked head. In this case the crack has extended down into the exhaust port below the new seat insert. This type of repair is a time bomb waiting to go off sometime in the future when this seat gets loose and falls out. more

[dingus]

Very rarely will we see a head with a crack between the inlet valves, but as the above photo shows, it can happen. When we see this, we consider the head junk, as attempts to fix these cracks have always brought nothing but failure and frustration.