View Full Version : M20 rocker arms and valve adjustment

04-16-2004, 11:51 PM
I've been racing E30 325is cars for 4 seasons, and just recently broke a rocker arm for the first time. Nice clean break, and no other damage to the new motor. In fact, I was able to change it with out pulling the head. The rocker shaft slides right thru the cam gear. I have two questions. Is this common on the M20? The rocker certainly appears to be the weak spot. Does anyone have and tips or trick to advusting the valves?

04-19-2004, 12:43 PM
Be very careful where you buy the rockers. I had a very similar problem on my 320i using cheaper aftermarket parts. Unfortunately, it took me a couple of times to figure out that the rocker would break first, then fall under the cam and snap it also. Never had the problem again when I switched back to OE BMW parts.


04-20-2004, 01:44 PM
I'm not too familiar with racing cars with pushrods... http://Forum.ImprovedTouring.com/it/wink.gif but can you just use the old Chebbie trick of tighten till they stop making noise, then another 1/4 turn?

Of course, just 'cause it works for the old Suburban doesn't mean it'd be good enough for a real racecar...

Vaughan Scott
Detroit Region #280052
'79 924 #77 ITA/GTS1

04-20-2004, 06:34 PM
Originally posted by 924Guy:
I'm not too familiar with racing cars with pushrods...

No pushrods here, just rockers.

Adjust to the factory specs w/ a feeler guage and a small allen wrench, unless you want to buy the fancy cust BMW tool...

Bruce Shafer
04-21-2004, 10:46 AM
What GKR_17 said. Always use OE BMW rockers bought at the dealer. I used these and never had a problem with my M20. I know others that had problems using aftermarket rockers.

Good luck.

[This message has been edited by Bruce Shafer (edited April 22, 2004).]

04-21-2004, 01:47 PM
joelg has had numerous issues with broken rockers. it is a relatively common m20 issue. my e30 m20 race car has run 4+ seasons with no problems though.


04-23-2004, 10:47 AM
I think it comes down to luck. There were 4 broken rockers (that I know of) at the bmw club race at vir last weekend, one in a an m20 and 3 in m10s.

none of them were mine for a change http://Forum.ImprovedTouring.com/it/smile.gif

Dave Ebersole
04-23-2004, 11:47 AM
There is usually a relationship between broken rockers and and a tach telltale needle, especially with aftermarket rockers. Get the rockers with the roundel on them.
Dave Ebersole