Cylinder Head & Rocker QuestionJust discovered that my M20B25 has broke a rocker ..

[dynoo]

Just discovered that my M20B25 has broke a rocker ..

Do i need the head off to fix this ?

What other things should i replace when im in there , water pump etc ?

For anyone who seen my other thread, had the rocker cover off changing round the injectors and spotted the problem.

I reckon its was the chip i put that raised the limiter, wee rocker couldnt handle the extra revs

Has anyone heard of uprated rockers ?

Cheers folks for any advice ,,,,

[jlevie]

Whether the head has to come off is mostly a matter of which rocker broke. If on cylinder 5 or 6, and the rocker shafts will move you can change those rockers with the head on the engine. For any other rockers you just about have to remove the head.

I've seen enough broken rockers on M20's that seldom if ever see the high end of the rpm band to form a theory that lack of timely valve adjustments and/or worn valve guides have a lot to do with rocker failure. The repetitive impacts start stress cracks which eventually cause the rocker to fail.

My recommendation would be to pull the head and refresh it (valve grind, new guides & seals, new rockers). Billet rockers are available as an upgrade, but they are pricey.