Rubber Noise Silencing Pads At The Cylinder
Head Fins
quietingpads.htm-57
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****See the valves.htm
article for more information about 'noisy valves'. ****
Background:
In 1985 BMW boxers came with a new type of rocker arm assembly with adjustable end play, by shims. The purpose was to quiet the valve noises. IMHO this modification did quiet the valves compared to a properly set-up earlier type. Many find setting up the earlier style a bit of a PIA, especially in the /5 era, when the rocker mounting was not machined to keep the side movement to a minimum. In any event, it costs $$$ to convert to the 1985 style. I've never liked, too much, the plastic parts in the 1985+, but they DO work OK.
For those of you that feel that cost is no object, ever, for your BMW, the entire kit for the rocker conversion for you older BMW is #11-33-9-057-699. You will also need new support bushings, part is #11-12-1-261-405. You might find a 1985 and later set of head parts in a wrecking yard though. Do not just try to add the shims to an earlier style, you need to modify their rocker arms.
In addition, at the same time, BMW decided that the addition of some relatively hard silicon rubber pads/inserts into strategic places on the fins, at top and bottom of the heads, would also quiet things, by stopping 'metal ringing' of the fins...sort of like hitting a bell,type of ringing. These DO help a small amount, and have no effect on cooling, maybe even help due to turbulence added.
These pads ('pucks' or rubber pads), are 11-12-1-337-818, no glue
needed. You need 24 of them to do both cylinder heads. They
are included in the kit mentioned above.
They are fairly easy
to install...one uses fingers and then a very blunt tool of some sort and taps them into position, trying to keep them round shaped. I
put a wee dab of adhesive on them...see below.
There are 6 of these pads used on top, 6 on bottom, of each cylinder
head. They begin, looking from the side, towards the
engine, that is, facing the end of the valve cover, between the 2nd and 3rd fins from outer.
Official spacing is measured from the center line of the spark plug (or valve cover center stud), both horizontally and vertically. The
horizontal spacing is 37 mm center of rubber pad to center of spark plug/stud. The vertical spacing is 65 mm down, and up
from that same stud.
NOTE: Contrary to the above BMW supplied information, the BEST position for these pucks is actually SLIGHTLY different than what
BMW states. The best position is such that the pad is at the CORNERmost of the fin, but fully touching
metal all around.
The BMW bulletin on this is May 1986 11-032-86 (2208).
This bulletin also covers the 1985 R80 rocker arm assembly changes (same as other models
actually). I suggest this conversion NOT be done, due to the cost, unless you can get
rocker gear from a late model wreck, cheap. BUT...this later rocker gear, while it
has some plastic parts, is definitely quieter.
The photo below is a scanned copy of BMW's bulletin, edited, of the reverse side. NOTE that MY recommendation for the pads is more towards the corner of each fin, where ringing is more pronounced; and, I have put lines on BMW's sketch to indicate moving the pads from BMW recommendation to closer to the spark plug. The pads are still fully on the fin, that is, no part of the pad is not touching the fin. There are differences in the head castings over the years, and you might not be able to place the pads exactly as shown in MY idea, nor BMW's. Close enough is good enough.
***There have been some reported instances of pads loosening and disappearing. Because of that, the last batches of pads I have installed I put in with a wee droplet of 3M Super Weatherstrip Adhesive onto the pad as I slide it into position.
Revisions:
05/15/2003: completely updated
05/04/2007: Add scanned copy of pad placement side of the SI, and some
notes, and clarified some details