How do you use the piston stop to locate true TDC?

It looks like there is a 14mm plug that you screw in where the spark plugs go, then there is a threaded bolt that can be adjusted. How do you know how far to thread it so it is a TDC.

 

Never used one before.. thats what the timing marks are for.

 

Yes, we all know that. But to get true TDC, people use the piston stop tool.

This is especially true when you are degreeing cam gears, it is a good tool to use in addition to the timing marks.

 

Take the cams out.

Place the cylinder of interest's piston at mid point. I've found that a back scratcher works pretty damn well.

Thread in the piston stop. Adjust as necessary so that it contacts the dome of the piston before it can pass through TDC.

Install degree wheel and pointer.

Rotate crank one way, until the piston contacts the stop. Mark the degree wheel.

Rotate crank teh opposite way, until the piston, once again, contacts the stop. Mark the degree wheel.

Find the midpoint of those two marks. That midpoint is your true TDC. Mark it and rotate the crank until the pointer points to your true TDC. At that point, you can either just leave the wheel as is, using the mark you made as your TDC reference, or you can adjust the degree wheel so that it zero's up to your true TDC.

Once you've got the pointer and the degree wheel sync'd, double-check your alignment. It it checks out ok, then never touch the pointer or the degree wheel alignment again.

Now you can install the timing belt, etc. If you can, turn the crank with the flywheel from that point on since using the crank pulley bolt as rotational leverage can potentially cause the degree wheel to come loose. Then you'll have to re-sync it again.

 

Thanks for the info.

 

I think there's a detailed explanation on the Crane or Comp Cams website.