325I BMW – 1988
This is the step by step process for a complete tear down and rebuild of an 1988 E30 325i cylinder head.I’ll try to point out all the tips and tricks throughout the process to save time and unneeded wrenching.
A little history on the car: I bought it from a friend of mine for $1,000. He had neglected his timing belt change so it eventually snapped and bent about 6 valves. The car shop quoted him $3,000 for a new motor. I gladly offered 1/3 of that thinking that I could buy a new cylinder head and be done with it. Things don’t always go as planned.
(Descriptions are below the images)

Before the tear down.

Valve cover, exhaust manifold and intake manifolds removed.

Cylinder head removed. Used head gasket still on the block.

The cylinder head is placed on its side on a workbench. Be careful not to place the head on the oil line or upside down on the table.

When the timing belt broke it caused interference between the piston and the bottom of the valve. The valve stem is slammed upward into the compressed valve and rocker arm. On the right you can see the broken rocker arm.

This is the oil line I mentioned a few pictures ago.

Loosen the valve tension by loosening the 10mm nut shown here.

When you’re ready to drive the rocker arms out of the cylinder head make sure you remove the retaining clip from the end of the head (cam gear side).

The head is cast aluminum and will break VERY easily.
(KEEP EVERYTHING ORGANIZED)
At this point you need to rotate the camshaft until exhaust rocker number 6 is under full load. Now you need to remove the rocker arm clips from the top of each rocker. Now drive the rod out of the head towards the back of the head. Once the first rocker has been taken out, rotate the camshaft so that the number one lobe (exhaust) is at it’s peak. Now drive the rocker shaft all the way out.

Use a suitable dowel rod to drive the rocker arm shafts out of the head.

Repeat the steps from above to remove the intake side.

With both rocker shafts and rocker arms removed you can now remove the camshaft. Just go slow.

Stripped down cylinder head.

Now you need a valve spring compressor to remove all the valve springs and retaining collets from the top of the valve stem.

Now with everything removed you can focus on cleaning the head or if it’s cracked you can start working on your cylinder head coffee table.

Clean the inside and outside thoroughly so that you can inspect it for any cracks or gunk.

Use a sharpening stone to clean the bottom side of the cylinder head.

Next go get yourself some lapping compound and a valve lapping stick. Be careful to only use a tiny bit of lapping compound and make sure you clean out all the compound once the valve seat has been reground.

This is my workspace in the basement. Notice the clean spot on the inside left of the closest cylinder head.

























Great writing, thank you.
I have a BMW 1988 325I. I just moved from Arizona to Montana, where it is frezing (0 to 30 degrees F). The engine failed to warm up at all or properly, and therefore there is no heat for the heater core. I have replaced it with new water pump, thermostat, fan clutch, cleaned radiator, cleaned heater core, verified heating valve at heating core opens and close properly (water circulates ok), but since the engine does not warm up, there is very litle to no heat to blow from the heater core. The two flaps for fresh air are shot closed with tape. Aparently all the air from inside the engine is blead out through the bleeder screw at the thermostat housing and at the coolant temperature probe. The engine temprature never got higher than the top of the blue mark on the temperature gage. The hoses on the engine barely are warmed. What can I do to correct this problem? Thank you for your input.
besides the broken stuff what would you typically replace when rebuilding a head and what do you use to clean everything?
The only thing that you really need to replace are the valve guide seals and the black end pieces for the rocker arm shafts. I generally spray everything down with some type of degreaser and then use an old tooth brush to get into all the nooks and crannies.
HEY BOOMER,
Thanks again for this awesome writeup. got my head off and it was damaged beyond repair due to a BROKEN valve, got a used good head off ebay and got it on my table at the shop got the cam sprocket off today and had to come back for a refresher course. I did have another question. as far as the sharpening stone can you be more specific like where did you get one, how big, all the details so that i get the right one. Thanks again!!!!!!!!!