Rocker arm shaft plugs
I was reading the Bentley manual and it says to remove the threaded end caps on the four rocker arm shafts. The machine shop said that there were none what they serviced the head. If there are none ,then are the cylinder head bolts the only thing to stop the shafts from working their way out of the holes?
Major Contributor
I got a '90 535 and there are tapped end plugs...
which I did not need to remove. They are about 1/4" deep in the shaft so they are not readily visible. Yes the head bolts and the end covers hold the shafts in place.
Grand Master
a good question. Does make one wonder why they exist. Hector is quite right, the head bolts and end plates do capture the rocker shafts and keep them from working out axially front and back. So why do the plugs exist?...since the internal thread for a slide hammer that can be used to extract the shafts is hidden and therefore not suseptible to harm...perhaps the plugs keep the internal end threads from buggering due to sludge, varnish etc. Function maybe is something as benign as mitigating valve train noise/quieting vibration. Or maybe the little plugs physically seal the rocker shafts for internal porting of oil pumped up to the top end to aid in lubrication of rocker arms if you see local oil holes drilled perpendicular/through each shaft adjacent to rocker arm positions. If anybody knows for certain, please post. Mine were intact in my head when I had it rebuilt. Loctite was used to secure the plastic plugs into their threaded bores when reassembled.
George
If the plugs aren't there I don't think you'll build up any oil pressure to lube the rockers because all the oil would drain back to the sump via the timing chain cavity. You'll also pressurize the cover on the rear of the head making leaks more likely. Earlier M30 engines, like my '83 533i had non-removeable covers. They weren't tapped either so you had to use a long drift to remove them.
Paul Shovestul
Originally Posted by George M
Grand Master
good stuff. Love your handle...Bellicose Right Winger...lol...hillarious. Sounds correct..the rocker shafts are hollow and have oil holes for lubrication to the rocker shafts. Obvious question then F1 FAN...is how do your rocker shafts and rocker arm bores look if you believe your head rebuilder and the plugs were nowhere to be found to begin with? In any event you do want to replace them for the good reason stated by our bellicose messenger. I would carefully have both shafts and rockers mic'ed for size. Some change rocker arms and shafts when rebuilding an M-30 head as a general rule.
George
Big, Big Time Poster
Glad to hear you like it George M. You too can get one if you want.....all you have to do is suggest that an OT post, taken way out of context is mere Liberal Whining and you'll be tatooed like I was. I'll wear this like a Badge of Honor.
Paul Shovestul
Major Contributor
...and as George alluded to, that is what I'm currently doing with my M30 head. I'm changing rocker arms and shafts as I found too much play between the shaft and rocker arm--more than what is speced in the Bently manual. Now I'm checking for valve play and hope that the tolerances are within spec. Forking out the "cake" to buy new ones is something I'm not contemplating.
Grand Master
I think some of the political threads that I have responded to in the past has already branded me as a right winger, which couldn't be farther from the truth. I am neither a card carrying Republican or Democrat. So yeah I can understand how one can be stereotyped into a particular category which makes it convenient for simple minded people who feel most comfortable with lableling people. I hope Paul you make a point to participate on this board to help elevate the knowledge base. Based upon your response, you seem to know a lot about these cars.
George
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