m20 head questions

[noE30]

So i've got my engine all tore apart because im replacing some gaskets, timing belt, water pump etc. And I was wondering if you all think it would be a good idea to get the head rebuilt while I have it off the engine. Should I replace the rockers while its apart as well, we all now they can be a weak point. Is there anything I should definitely replace if I do this? like new springs, retainers, rockers, or any else??

Thanks a lot !!

edit: the engine is a m20b25 out of my 89 325i just so you know.

[SpecM]

It would be a good idea to have the head cleaned up and the valve stem seals replaced, but as for the hard parts... that depends on your intentions with the car

[noE30]

well as of now I just want to drive it and maybe do some simple mods to it like exhaust and a suspension rebuild. Down the road I really want to swap an s/m 50, so thats why I dont really want to put alot of money into this engine.

I think im just gonna get the seals replaced and then any other parts that need replaced, so if the stock rockers are good still then I will just leave them be.

[SpecM]

the stock rockers should be fine as long as you don't bounce the engine off the revlimiter... exp if you plan to swap it later

[nando]

I would do springs, rockers, and if the cam has any wear, replace it with a new stock one.

cast rockers fatigue as they age and it's much easier to do them now. the springs also gets soft which leads to broken rockers through valve float at high RPM.

[jlevie]

I've seen enough cases of broken rockers to formulate a theory as to why they break. Some cases are on track cars that see the high end of the rev band, but other cases are on street cars that never see high rpm. So high speed operation isn't necessarily the cause. My theory is that the prime cause of rocker failure is excessive valve lash from a like of timely valve adjustments (say every 10-15k). Excessive valve lash impact loads the rockers.

While the head is off, a valve job and new seals would be the minimum in my opinion.

[nando]

yeah, basically anything that makes the rockers smack onto the cam face/valve is going to break them - be it poor adjustment, worn springs, or over-reving them. Plus as they age it's more likely they will break from these causes.

I have about 60,000 miles on my head and it's survived a lot of 7200rpm with new stock springs.. but I do make sure everything is adjusted/tight.