Dial Indicator Setup (Deck Height)

[930LDR]

I'm trying to figure out the best way to setup and use my dial indicator to measure deck height on my flat top 3.3L CIS pistons / Cylinders. Seems to me you would need to mount the indicator to allow you to set it at 0 when the piston is at top dead center and then measure then rotate it over to measure the span between that and the top of the cylinder but I can't imagine you'd retain any accuracy once you moved the mount.

Probably missing something very simple in my logic.

[304065]

Rob,

It's call the "Jo block" method or Gage block. (Hardly anyone calls them Johansen blocks anymore).

The procedure entails using a depth gauge base on your dial indicator, resting on a pair of identical gage blocks, which in turn rest on the edge of the cylinder.

• The indicator, base and gage blocks are placed on a flat surface like a surface plate or piece of glass
• The indicator is moved down so that there is slight preload on the tip (needle moves off zero) and then the screw holding the indicator is tightened
• The gauge scale is turned to set zero opposite the indicator position
• With the indicator zeroed, the entire stack is picked up and moved to the top of the cylinder. The gage blocks rest on the cylinder edge
• Holding the stack tightly, the crank is rotated to bring the piston to TDC.
• At TDC, the indicator point will be depressed and the indicator will read the sum of dome height and deck height. Subtract the dome height to get the deck height

Here is a photo of when I used this method to measure deck. Note that you need an indicator with a stroke greater than your anticipated dome height. A 25mm travel indicator would be fine.