Yeah Max, your absolutely spot on (apologies for the pun ... Ha!) I've probably done three or four engine re-builds over the last 20 or 30 years and tack welding the spacer plate to the crankshaft lobes (I think Norm K referred to them as flywheels) to lock the crankshaft in position before removing the crankpin and conrod has worked well for me and I've never had any adverse consequences from the procedure. Of course the procedure relies on crankshaft alignment being correct in the first place but I think this a relatively solid assumption. And of course, you're absolutely correct, the tacks don't put sufficient heat into to crankshaft to rise its temperature sufficiently to cause distortion. Any localised stress of minor strain at the point of the tacks is ellimated as soon as the tacks are cut out with the angle grinder wheel. Norm - I've never checked the alignment after this procedure because I don't possess the necessary equipment and tooling to do the check.
The attached photo shows the now very "weathered" spacer bar that I've used over the last 30-years but its still sufficiently serviceable to do a few more jobs if I feel the need in my "wind-down" years which is most unlikely, I may add.
