M20b27 cylinder head rebuild

[Thunderzol]

Hi R3v,
I took my cyl head off and exhaust/intake manifolds. Do I have to remove anything else, like the camshaft? And what’s a reasonable ask for a machine shop to complete before putting the head back over my new head gasket.
thanks!

[jbontke]

Find a machine shop and they will tell you what they need removed (I had to pull the cam). I think I was going to spend $140 for: magnaflx for cracks, valve guides, valve job, skim head.

[digger]

Take it to a good shop, they will tell you what's wrong but basically ask for
- clean,
- pressure test
- check guides and valves
- valve seat job / valve grind and seal test
- check cam and rockers
- light resurface

for parts you'll probably want new valve stem seals, O-ring for the cam retainer /thrust plate, rocker shaft bungs and rocker cover gasket

[ForcedFirebird]

Take it to a good shop, they will tell you what's wrong but basically ask for
- clean,
- pressure test
- check guides and valves
- valve seat job / valve grind and seal test
- check cam and rockers
- light resurface

for parts you'll probably want new valve stem seals, O-ring for the cam retainer /thrust plate, rocker shaft bungs and rocker cover gasket

^^this

I do a ton of m20 heads, and since it's an eta, it will be far less worn than a b25 in most cases - based on experience.

Most cylinder head shops will take the head whole, and give it back that way, ready for installation, valves adjusted etc. Make sure you ask them if they have done BMW single cam OHC's before, many like to beat the rocker shafts out, which is unnecessary. Removing the rocker arm retainers, then rotating the cam as you slide the rockers around, they will be able to rest with none under spring tension. Then the rocker shafts will then slide out by hand.

About 60% of the heads that come through the shop have worn exhaust guides, the intakes tend to be within tolerance. Make sure they don't line the guides, these are bronze already and should be pushed out/in. The ID is 6.98mm, not 7mm, before we did heads in-house, the local shop was setting the worn guides to 7mm FTL. They are looser than old ones at that point.

The 200 castings crack far less than 885's (amusing yours is NOT an 88, which is a seta), but they do crack on the coolant passage to exhaust valve seat on occasion. The 885's crack under the cam, and often go through the #6 cam journal which isn't used in the 200 (200 castings have 4 cam bearing bosses, #1, 3, 5, 7 - 2,4,6 are not drilled for oil).

Most valve surfacing machines will also grind rocker pads. If your pads are pitted/worn, it's a quick process to refresh them - a must when using a new camshaft (or use new rockers).

[Thunderzol]

Thanks for all the great feedback. I’m glad I haven’t started taking the rockers and cam out. Anyone recommend a good machine shop in North California?

[McGyver]

Thanks for all the great feedback. I’m glad I haven’t started taking the rockers and cam out. Anyone recommend a good machine shop in North California?

Where in NorCal?

I have my stuff with Shawn at Star Machine Shop in Emeryville. There's probably a handful of other good BMW machinists in the area. You could also ship your head to BimmerHeads in LA.