Hi All,
I am in the process of buying a 320 with an m20b25 swap although one of the rocker arms have broken. I have read up and it doesn't seem that difficult to replace but I have a spare m20b25 engine lying at my parents house, so would I be able to take the head of the spare engine and replace it with the one thats got the broken rocker arm? If so would that be much easier and straight forward as I can then have the head off the other one and do a full rebuild of it?
Thanks
Corrie
Broken Rockaer, can i just swap the head?
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jimmyspeed
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from the wiki page - Rocker Arms
The valves are opened and closed by rocker arms, which are pressed on by the cam. These rocker arms perform a dual function of cam follower valve adjuster, as one end contains the eccentric and the adjustment nut. The rocker arms pivot around rocker arm shafts.
If you have broken a rocker arm, they can be easily replaced by removing the rocker cover. If, however, you are suffering from repeated broken rocker arms, it is more likely that you have bent a valve and will need to remove the head.
To remove a rocker arm, you must remove the rocker arm shaft. This is possible with the head still in place, but may require lifting of the engine to allow the shaft to exit the engine through the front.
To remove the rocker arm shaft, remove all the adjuster eccentric discs and all the clips locating the rockers. Push any rockers that are loose sideways to clear the valves, turn the engine until the remaining rockers come loose (i.e. on the heel of the cam lobe) and push them sideways as well. Rocker shaft should now slide out easily, as long as you've removed the bar that locks both shafts in place at the front of the engine. If you have already removed the timing belt, then ensure that no pistons are at TDC (put crank at 60 degrees past TDC mark) and turn the camshaft. When you put things back together, set the cam mark at 30 degrees past the mark, put the belt on, turn the engine carefully back to TDC, and check the belt isn't a tooth out.
The valves are opened and closed by rocker arms, which are pressed on by the cam. These rocker arms perform a dual function of cam follower valve adjuster, as one end contains the eccentric and the adjustment nut. The rocker arms pivot around rocker arm shafts.
If you have broken a rocker arm, they can be easily replaced by removing the rocker cover. If, however, you are suffering from repeated broken rocker arms, it is more likely that you have bent a valve and will need to remove the head.
To remove a rocker arm, you must remove the rocker arm shaft. This is possible with the head still in place, but may require lifting of the engine to allow the shaft to exit the engine through the front.
To remove the rocker arm shaft, remove all the adjuster eccentric discs and all the clips locating the rockers. Push any rockers that are loose sideways to clear the valves, turn the engine until the remaining rockers come loose (i.e. on the heel of the cam lobe) and push them sideways as well. Rocker shaft should now slide out easily, as long as you've removed the bar that locks both shafts in place at the front of the engine. If you have already removed the timing belt, then ensure that no pistons are at TDC (put crank at 60 degrees past TDC mark) and turn the camshaft. When you put things back together, set the cam mark at 30 degrees past the mark, put the belt on, turn the engine carefully back to TDC, and check the belt isn't a tooth out.