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). Ensure to also order bolt 11311714798 as it is a slightly different length.

**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.