So you’ve heard that you should change the timing belt on an M20 every 50k miles or 4 years (whichever comes first), because in case of failure the valves will hit the pistons, rocker arms will break, and you’ll be looking at a top end rebuild or a new engine.

But what many people, even seasoned miss is that there was a late revision to the intermediate shaft sprocket gear; from stamped metal to sintered.

Left old style (11311713351), right new style (11311717398). The new style calls for bolt 11311714798 (35 vs 28mm long M10), but either bolt can be used successfully.

**During install, on the new style, the casted in nub goes into a matching hole on the intermediate shaft.

What happens with the old style? Catastrophic failure from rust and fatigue leading to the same result as the timing belt breaking:

Although many 1988+ cars should have the new style, its possible to have the old style all the way up to 2/16/1989 (some MFG plants switched over before others):

Much less common is for there to also be a stamped gear on the camshaft; generally only on 1986 cars; if that is the case, also change to the newer style sintered gear (11311714988):

This entry was posted on March 8, 2023 at 11:56 am and is filed under Do it Yourself. You can follow any responses to this entry through the RSS 2.0 feed.