Depends upon the pulley used, and how much of the boss was machined away to gain clearance. Some people go overboard and do not leave enough to be useful, and some pulleys require more to be removed than others.

Mines a DD with a bit of tricks. Not a track or club car . I really dont care about that boss. I`m living on borrowed time with 144000 kms anyway.

How much further do you expect the engine to last before imploding?

Regarding underdrive pulleys. Why not file a small mark in the pulley and punch a mark in the block. There is no locking pin on my 951, you lock the flywheel instead. As long as you have a mark would this not be possible?

On the M96/97 you have to lock at the pulley to do any cam related work or an IMS retrofit (the flywheel is out of the car for the latter).

I should have thought about the IMS procedure.

How about drilling and tapping a hole in the pulley and then drilling a small matching dimple in the block to accept a set screw? If this is done while the engine is locked at TDC via the flywheel it should be very accurate. Would this be enough to hold the timing during the procedure?

There are tools to lock the flywheel from the starter crown gear.
And without the flywheel, there are tools to hold the crankshaft by the flywheel mounting holes.

But without the pulley and the locating boss, finding cyl 1 TDC takes longer.

Take a look at an untouched engine case; the boss for the pin to lock the crank is substantial, and the pin itself is 5/16 steel. A set screw isn't going to cut it, and I would be remiss if I didn't caution anyone about drilling into the engine cases, which is a very bad idea.

And which is why we have a substantial surcharge on IMS retrofits or any cam related work on cars that are already fitted with under drive pulleys. If I have to pull your trans to do a job that normally doesn't require it (e.g.: VarioCam repairs), you are going to pay for the privilege.

Of course, I understand completely!
I was just saying that there are other ways that would work while doing the IMS.

Can those of you that installed the underdrive pulley from Pedro, explain/show how you held the pulley to re tighten the bolt? The pictures of his pulley I've seen don't show any holes to use a pulley holding tool.
Thanks!

A better solution is to save your OEM pulley, label it, toss it in your spares bin and don't shave off too much of the timing boss. This is what we did and the IMS retrofit was reasonably uneventful. It took an extra 30min or so to re-install the original pulley and align to TDC. Lock it in with the factory pin and we were good to go. Most shade-tree tuners don't think this far ahead and get in trouble when the motor needs internal work.

PPPPPP

^ +1. Shave as little as possible off the boss. I have had to reinstall the original pulley to adjust the cam timing. It would be an even greater hassle without the boss.

I got a mate to lock the flywheel with a large and strong screwdriver. There are some gaps between the bellhousing and the block where this can be done. Make sure you know which way it will spin when you tighten. That way I was able to properly torque the bolt without the engine turning over.