EVO 1340 Timing Marks Explained: Gears vs. Ignition Timing

ByThe Answerlode Editorial Team

Understanding EVO 1340 Timing: Gear Alignment vs. Ignition Timing

The 1340 EVO has two completely separate timing procedures—gear timing and ignition timing—and they have nothing to do with each other. Mixing them up is the most common source of head-scratching frustration on an otherwise solid build.

Gear Timing Marks: Getting the Valvetrain in Sync

Gear timing is purely mechanical. The marks on the crankshaft (pinion) gear, camshaft gear, and breather gear all need to line up to put your valves in the correct sequence with crank rotation. Get this wrong and the engine won’t run right—full stop—regardless of what you do with ignition timing later.

Three marks to find and align:

  • Crankshaft (pinion) gear mark – Usually a dot or slash mark stamped into the gear
  • Camshaft gear mark – Lines up with the pinion mark; the cam gear may have two dots, and only one of them aligns correctly with the others
  • Breather gear mark – Small and easy to overlook, but it has to match up or your breather timing will be off

Once you have them aligned, rotate the engine a full 360 degrees and check again. They should still line up. If they’ve drifted, you’ve got a gear indexing problem. Also worth noting: the pinion gear is keyed, so it only goes in one way—there’s no ambiguity there.

One thing that trips people up: when all three gear marks are properly set, the TDC mark on the flywheel may not be centered in the inspection hole. That’s intentional. Cam gear alignment marks have nothing to do with piston TDC—they’re a separate reference system entirely, and chasing both simultaneously will just cause confusion.

Ignition Timing: Setting When the Spark Fires

Ignition timing is about when the spark plug fires relative to piston position. It’s controlled by the ignition module and verified against marks on the flywheel, which are visible through a small inspection hole on the left side of the engine case near the timing cover plug.

Two flywheel marks matter here:

  • TDC mark – A vertical line; piston is at the top of the cylinder. Not used for ignition timing adjustment.
  • Advanced timing mark – A dot or alternate symbol, typically around 35 degrees before TDC (BTDC). This is what you’re actually aligning to when you set ignition timing.

To check or set ignition timing, remove the timing inspection plug from the left side of the motor. Clip a timing light to the front cylinder spark plug wire, start the engine, and bring it to a stable idle—roughly 900 to 1,100 RPM. Point the light into the inspection hole. The advanced timing mark should appear centered in the hole when the spark fires. Adjust the ignition module plate until it does, then lock it down.

If you’re running a Dyna S or similar mechanical advance unit, look for the two-dot advance marks in the hole rather than the TDC line when doing static timing. Always cross-reference with your ignition module’s own instructions—specs vary by module and by model year.

The Key Difference: In Practice

Short version:

  • Gear marks = mechanical sync of the valvetrain (set it during assembly, then leave it alone)
  • Ignition timing = when the spark fires, verified through the flywheel inspection hole on the left side of the motor (adjusted at the ignition module or points, if applicable)

A lot of EVO builders set their gears, feel the engine turn over cleanly, and assume they’re done. They’re not. Gears in sync is step one. The ignition still needs to fire at the right moment—and that’s a separate check with a separate procedure.

Pro Tips for EVO Timing Work

  • Replace the solid timing hole plug with a clear plastic one after your first timing check—it keeps oil off the timing light lens and makes every future inspection cleaner and faster
  • Put a small dab of white paint on your ideal timing mark position so you can find it at a glance during future adjustments without hunting for it
  • Timing specs vary across EVO model years (the engine ran from 1984 to 1999) and between ignition modules—use your specific year’s service manual, not a ballpark figure from a forum post
  • Starting from scratch? Put the front cylinder at TDC on the compression stroke, then use a timing light to dial in the advance curve from there

Sources

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