Deck Height Measurement Question

[Topend]

  I am trying to get a measuremeant of my current deck height then measure the current piston from the pin to the top of the piston so I can get close to zero deck height. I want to send my jugs to be bored and fit with new pistons. I want to give them the height of the old pistons from the pin to the piston top & compare the new piston height to the old ones and if needed trim the jugs to get zero deck height.
  I have the deck height dial indicator tool I purchased from someone who makes them on this site. I used a glass window to zero the gauge after cleaning the glass and tool. I seem to keep getting different measurements. Mostly .00125" to .0015 but sometimes is is a + .003 ?? I am going on the outer lip of the piston above the pin. (I have forged SE high compression pistons) I can feel the lip with my finger piston being in the hole. I have cleaned the head & piston outer edges with brake cleaner etc.
I have the jug snugged down with 2 head bolts with spacers under them. The rings are still on and the O ring under the cylinder. I have not yet pulled the jug off the motor yet. Should I take the O ring off the jug then snug down the head bolts to get a better reading? Should I just use a feeler gauge and stright edge? Any suggestions?

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[blkfalc4]

Leave the oring on. Don't know what to tell ya on the differing readings.

[Jeffd]

your piston will rock a bit and readings can be different.  use an old .030 steel head gasket and use soldier in a cross pattern taped to the top of the pistons extending to the outer edge of the piston.  torq the head down spin the motor over by hand of course and then remove the head and measure the soldier with a micrometer.  That is how I did it and the squish area measured .030-.032

[PoorUB]

  I am trying to get a measuremeant of my current deck height then measure the current piston from the pin to the top of the piston so I can get close to zero deck height. I want to send my jugs to be bored and fit with new pistons. 

Pesonally I would bore the jugs, put on the new pistons, less rings, and then measure the deck height. Less chance of making a mistake this way!

[Horizonmech]

you really  should do it as PoorUB suggests, we all get you are trying to save a step in between ( especially when the pistons and cyl's have already been at the machine shop for 2 wk's) but you are setting yourself up for inaccuracy, it can be done mathematically but you will get a much more accurate measurement using the cyl's and pistons you are going to run....it's a bit of a pain to have to stop and backup if the numbers are off but it's your ride, maybe it will come out right the first time...

[djl]

Pesonally I would bore the jugs, put on the new pistons, less rings, and then measure the deck height. Less chance of making a mistake this way!

then the straight edge and feeler guage. IME, there's not enough difference in CR between 0.00" and 0.0015" deck height to worry about.   

[Topend]

Yep I think I will wait and see how they turn out with the new pistons first. If I am lucky maybe it will be .002" or less. 

[WVULTRA]

Topend95:

I used the procedure of checking above the wrist pin on both sides via this method shown by poorboy:

http://harleytechtalk.com/htt/index.php/topic,8628.msg88500.html#msg88500

Worked perfect for Axtell build.  Really helps if your after specific squish/height from the pistons, cylinders, & head gaskets.

[Topend]

WVULTRA,
That is the way I checked my pistons I am removing now. Indicator on the outer edge because of domes. But I am a little leery of the readings because my front cyl. was .002 on one side and .0065 on the other side. So I figure about .004" in the hole if you split the difference??