Hey All -

I'm replacing my timing gears on my Disco II and stupidly turned the crank with the chain off. I'm afraid I may be 180 degrees off.

Any ideas on the best way to check for TDC? I can align the marks on crank and cam pulleys easily enough but I want to ensure that I'm starting from the right reference point.

 

Is the engine still together with only the timing cover removed?

 

Yes. I have the front timing cover off but otherwise the engine is still together.

I had a thought that maybe I could remove spark plug #1, plug the hole with my finger, turn the crank, and stop once I felt compression. That might get me in the ballpark.

 

The weird thing is that I can't find any information online or in the manual on how to set TDC. What do you do when you're not thinking and make a stupid mistake that misaligns the cam and crank.

The book only describes that the timing marks should be set to 6 and 12.

 

Yes. That is the old school trick. That or pulling the dipstick out and sticking it through the spark plug hole to feel when the piston comes up.

Unfortunately, you won't know whether the piston is coming up for the compression or exhaust stroke. The mark on the crank pulley is going to be oriented correctly on both strokes.

Short of taking off the valve cover to see which valve is opening as the piston travels up the cylinder, I guess you could remove the exhaust manifold on the left bank and place your hand or something over the port on #1 to see when pressure is felt.

 

Wait a minute... If you don't have the chain installed and the camshaft isn't turning...

It shouldn't make a difference which stroke it is.

 

I never aligned the camshaft to the 6 oclock position before removing (so it's about 4:30) and I did not turn it after removing the chain.

I've turned the crank shaft several times though. This is my first Rover (so I don't know whether this works differently) but wouldn't that mean I could be out of alignment even if the timing marks are lined up?

 

Won't make a difference. Just rotate the cam until the mark is at 6:00 then rotate the crank so it is at 12:00.

I think you and I have both been WAY over-thinking this. When the cam gear is at 6:00 and the crank gear is at 12:00 the number 1 will be at TDC. When the crank gear is at 12:00 the piston will be at TDC of either compression or exhaust. It doesn't matter because since the chain is off, none of the valves are moving.

Just rotate the cam gear to where it should be, then rotate the crank to 12:00.

 

Yeah, I think you're right. We've been stuck in a thought spiral.