Check end play with flywheel seal in? Options

[bbrock]

I think I already know the answer to this, but before I ruin an unused seal, I thought I'd get a ruling from the judges about whether you can get a good end play reading with the seal in place.

Thirty years ago I rebuilt the bottom end on my 2L engine and checked the end play with a feeler gauge. Then the project was put into deep sleep for decades before I finished the rebuild. Now I'm finally doing it and would like to recheck my work with a dial indicator just to be sure. So I set up my indicator on the flywheel and pulled the flywheel away from the case followed by a few very gentle taps on the impeller end of the crank shaft with a plastic mallet until it stopped moving. Zero the gauge and then squeeze the flywheel into the case with my hands. When I squeeze hard, the gauge reads about .0035" and when I let go, it moves back to about .002". I'm assuming the spring back is the seal pushing the crank back out a little. Would it be stupid to think I'm okay here?

I actually have a spare NOS seal I bought back when I started the rebuild. All I can find stamped on it is the size and FPM/ACM which I believe tells the inner and outer rubber material.

TIA

[Mark Henry]

I've built VW AC engines for 30 years, I never use a dial indicator for end play.
In the 90's my tool and die, machinist buddy bet me a round that his dial indicator was more accurate than my feeler gauge. It was a draw, we bought each other rounds.
I use the simple $10 feeler gauge fixture and a good set of feeler gauges.
Put the engine at TDC, clean a spot, bolt on fixture, pull on the fly, set screw, push in, feeler gauge. Done.

If it's "popping back" it has a load on it. is the fan belt off? I set it at TDC when I do endplay.
Or is it gorilla grip syndrome? A guy with gorilla grip could bend a flywheel .002...which would be seen on the dial indicator.

Use a new RM seal AND flywheel O-ring, but leave the O-ring out till you have set the endplay.
I'd do the pilot bearing, lock washer and felt seal as well.