When is the best time to measure the end play during an engine rebuild, before or after installation of the cylinders and pistons, or doesn't it matter?

Thanks

I do it when I am ready to install the flywheel.
You can measure it whenever you like, but you cannot set it until you have the flywheel installed.

I tend to install the flywheel early to help me turn things easier and lock down the crankshaft when needed.

For me, the flywheel gets installed soon after the case is bolted together and before the Pistons and cylinders......just so I have something to grab onto.

You can do it before you assemble the case with feeler gauges.
You put the bearing on, then a stack of 3 shims and then the flywheel.
You want .003-.005, I'd go for slight drag on .004 if doing this.

I have done this in the past and it works fine, I of course double checked my results.
I got this trick from Gene Berg himself when talking to him about my engine I bought from him in 1991.
I don't do it most the time because honestly I usually forget to do it this way.

I have a dial indicator now, I have also used the VW tool with a screw and feeler gauges.
They all get the job done.

Curious why you would do it like this?
Is it just an easier way to measure, or is there something you are looking for before you close the case?

Every one has feeler gauges and it works fine in a pinch, I had my doubts as well but it works. Gene did know his poop, likely they learned this trick at the drag strip.
When checking 911 endplay I know it's bit different but it's basicly the same check.
Only issue is you have to keep track of your shims till you're ready to install them.

I just got done doing this, I didnt measure until after the pistons and cyls were in place, so I dont have the before measurement, but it seemed to me that the 'end play' was much greater before I installed the pistons and cyls. This makes sense as the connecting rods would have no limit on fore-aft movement without the pistons and cyls in place.

When I did measure, was spot on with my shims at .1mm. According to the factory manual, the end play is .07-1.3MM, and the wear limit is 1.5MM. This is for a 912E.

Yes, this is why I asked the question. On a previous engine rebuild (a 912) the end play was almost non existent after I installed the P&C´s. I removed the cylinders and heads to double check and the end play was once again within spec.

Any thoughts on this... anyone

It should not change if the parts are all in spec.
It's all about the crankshaft movement, the rods should not stop it or they are rubbing where they should not be rubbing.

Stupid question but here goes....
When I rebuilt the 912 engine I followed Harry Pellows advice... Harry is supposed to be a guru in the 912 engine world. Harry recommends making up a assembly lube from equal parts of mos2 grease and STP its pretty viscous stuff.

Here comes the stupid question.. could this gook have stopped the con rods sliding on the crank and piston pins?

The engine started and runs no problem.

I'd say slow the movement down, but it shouldn't have stopped it. You do have to be more forceful to properly/fully move the endplay. I also turn the flywheel a bit as you do this. After you have done it back and forth a few times it should be slightly easier to move.

Some builders do not like moly on engine bearings. Old builders are funny, hate to try new new things and like to stick with what has worked for them in the past.
I mix oil with a bit of blue (not red) STP as assembly lube. I dip the pushrod ends in STP as I assemble. This is the only time I ever use STP.
This is Type one and 4 engines.

For the /6 I used Clevite 77 assembly lube, mostly because there are more sealants to contaminate if you drip oil during assembly. It's not super thick I'd say halfway between an oil and grease, but it sticks and won't drip off.
I liked the Clevite lube and it's made by Mahle, I'd think Clevite/Mahle should know a bit about bearings.