I am in the midst of replacing my timing chain, etc, and walnut blasting the intake valves. The timing chain was difficult but I managed to complete it. I walnut blasted cylinder #1 and it seemed to work out ok, but I still need to go back and hit a few spots. I then did #3 and it took a while because the valves were heavily coated. Each time I went to a cylinder I found TDC on the power stroke by using a small piece of paper stuck in the end of my leak-down tester hose. I used the same technique on #4 and I could not detect TDC and had to resort to the leak-down tester to determine TDC. I then retried the tissue technique on the other cylinders and the same no joy. What gives?

 

Get some wooden kabob sticks, remove the spark plugs, one stick into each cylinder. Then rotate the crank.
If you know where #1 TDC is, just follow the firing order of 1-3-4-2

 

I used ROMEX electrical wires. I cut 4 equal wires to 1½ foot long. When all the ends of the 4 wires line up in height, You have reached TDC. Look at the hole in the transmission bell housing. You should be able to insert the flywheel lockpin with ease.

 

Vanski, technically you are incorrect. When all for wired line up, you have set the engine in the 90 degree position not TDC on any cylinder. TDC for cylinder 1 would be when the piston reaches the top of its stroke (compression stroke) and so on for the other cylinders.

Hal, you may have confused the audience. In your post you started with a sentence about changing your timing chain (engine is set to the 90 degree position); then you went on to discuss walnut blasting. A perfect TDC position of the piston is not required for walnut blasting; you only need to make sure the intake valves are closed on the cylinder you are cleaning. The intake valves will be closed at any point along the compression, power, or exhaust strokes.

 

Allow me to add to this. Yes put the "wooden kabob stick" into spark plug hole #1. Rotate the crank until the you find TDC. Check the lash on all 4 rocker arm on #1 cylinder. If it is at the TDC compression stroke there will be some play in valve lash (clearance, all valves closed) on ALL 4 valves. If not rotate the crank 180 degree and recheck. The firing order is 1-3-4-2 so to get the the next #3 TDC compression stroke rotate the crank 180 degrees and recheck.

 

Check the lash between what? Did you mean check the lash between the tip of the valve stem and the drag lever? Between the intermediate lever and the drag lever?

What is your technical reference for all of this? I have never seen a valve lash adjustment procedure or even a specification for valve lash.

Put whatever tool you like into the cylinder, when it stops rising, you've hit TDC.

 

Ahhh ok.... thank you mkov608 for the clarification.

 

Sorry old school terms. When the cylinder is at TDC it is either on the compression stroke or exhaust stoke. You have to determine which one . At the TDC exhaust stoke the intake valve are closed and the exhaust valve are open. At the TDC compression stroke all valve are close so the cam lobes should not applying any lift pressure on the valves and there should be slight clearance/movement between the rockers and valves on both intake and exhaust valves. Another way to find the compression stroke but it difficult on the Mini since the plugs are so deep is the place on your finger on the plug hole. You will feel the pressure build up as you cycle through the compression stroke. In the old days it was simpler since there were the timing marks on the crank pulley and the distributor rocker arm position to determine the compression TDC.

 

On other types of engines you are correct, but this is a variable valve timing engine. There is no play between the roller drag levers (what you are calling rockers), and the stems of the valves (intake or exhaust). The lobe on the intake camshaft is in direct contact with an intermediate lever (with rollers); in turn, the intermediate lever depresses the roller drag lever, and it depresses the valve stem. The eccentric shaft changes the pivot point of the intermediate lever thereby changing the lift of the intake valves. Springs hold tension on the intermediate levers so there is no play between the roller drag lever and the stem of the valve, even at TDC.