I doubt 2500 rpm would be considered anything critical,normally, in fact will be more like idle speed.
Built quite a few running and frequently used engines in my time(without needing any whirring motion calculation....what evere it might be) and this simply doesn't look right without any...
Still pencil scale drawing, measurements (all) and process this end, so don't end up turning away a piece one is meant to hold the job by.
Even using drawings from others I tend to write my own measurements as mistakes can come up on drawings , and I rarely ever follow the plan to a tee.
Actually they can and do contain magnesium.
Where do you think the term " mag wheels" came from?
We have also come across alloy containing magnesium in motorcycle engine crankcase.
Point being, it's not all " she'll be right bloke".
Personally I couldn't care less what you think is ok or what...
Throw some in a crusible with enough heat or existing molten metal and you'll have glorious fireworks.
Think you need to be responsible here and show others who have no idea, that adding magnesium content can be rather dangerous instead of passing it off as " ah....no worries bloke, I do it all...
I'd tend to be more than hesitant at using anything from car rims given the possibility of them containing magnesium.
Why, I'll let you all find out for yourselves....suffice to say, rather spectular fireworks at time of meltdown.
Best to do some drawings.
Positioning of holes become paramount especially with 4 cylinders.
.......and there are plenty which you do not want to intersect.
......and then there are those which must end up in the correct place starting from some obscure angle.
Possible you can show some details on the ignition system "you built"......include any circuit diagram "you used" and what power supply "you used>
Also details on the parts used.