Locating and Setting Engine to Top Dead Center (TDC), Cylinder 1

Overview

This procedure guides you through setting the engine of your Porsche 944 S / S2 (16v) to Top Dead Center (TDC) for cylinder 1 on its compression stroke. This is a critical step for tasks like timing belt replacement or engine rebuilds, ensuring the crankshaft and camshaft are perfectly aligned to avoid damaging pistons or valves.

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Tools Required

• 24mm (15/16 inch) deep socket (or shallow socket with a 25-50mm (1-2 inch) extension)
• Ratchet
• Flashlight
• Step stool
• Flywheel lock tool 9206 (optional, depending on additional work)
• Small diameter wooden dowel (optional, for alternative method)

Step-by-Step Procedure

Step 1: Locate the Clutch Housing Window

1. Stand on the left side of your Porsche 944 S2 and look toward the back of the engine compartment.
2. Find the square opening (window) in the top of the clutch housing. This is where you’ll spot the TDC mark. It’s close to the speed/reference sensor mounting bracket.

Step 2: Prepare to Rotate the Engine

3. Before rotating, ensure the timing belt is installed and properly timed, or the camshaft housing is removed. This prevents valve or piston damage on the 16v engine.
4. Grab your 24mm (15/16 inch) deep socket and ratchet. Attach them to the crankshaft pulley bolt at the front of the engine.

Step 3: Rotate the Engine to Find TDC

5. Turn the crankshaft clockwise. Watch the clutch housing window for the letters “OT” to appear on the flywheel.
6. If your flywheel is rusty and “OT” isn’t clear, look for a painted line (some owners mark it with nail polish). Use a flashlight if needed.
7. Keep rotating until the scribe mark (a line next to “OT”) aligns with the tab inside the window. The tab is on the side closest to the car’s center.

Step 4: Verify Camshaft Position

8. Check the camshaft sprocket to confirm you’re on the compression stroke. Look through the opening in the distributor housing cover (just above the distributor cap) for the alignment mark.
9. If the camshaft mark isn’t aligned, rotate the crankshaft one more full turn (360 degrees) and recheck the flywheel and camshaft marks.

Step 5: Alternative Methods (Optional)

10. If you can’t see the “OT” mark clearly, look underneath at the bottom of the clutch housing near the starter. Find a 5mm (0.2 inch) wide groove in the flywheel. When it’s centered in the opening, cylinder 1 is at TDC.
11. Or, remove the #1 spark plug, insert a small wooden dowel into the hole until it touches the piston, and rotate the engine. When the dowel reaches its highest point, you’re at TDC.

Step 6: Lock the Engine (If Needed)

12. If you need to remove the crankshaft pulley bolt or keep the engine at TDC, install the flywheel lock tool 9206. This fits when the engine is in the car.

Post Procedure Checklist

• Double-check that the “OT” scribe mark aligns with the clutch housing tab.
• Verify the camshaft sprocket mark is visible and aligned in the distributor housing cover.
• Ensure the engine rotates smoothly by hand (if safe to do so) to confirm no valve/piston interference.

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manual, Volume 1
• Youtube