Forum » General Engine Building Discussion » So I've found True TDC and marked my crank pulley, now what (possible stupid question alert)

So I've found True TDC and marked my crank pulley, now what (possible stupid question alert)

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Sorry if this one is a stupid question. If I find True TDC for the purpose of re-marking my crank pulley with better precision should I be pulling off my timing belt and using my new mark to re-time the engine?

And if I do re-locate the timing belt using the new TDC mark, what about if the teeth of the belt don't allow you do do so with such exacting precision? I feel like odds are they will not and that the factory not-super-precise mark is there for this reason?

If you want perfect cam timing you will need vernier gears, if it is variable valve timing it doesn't really matter as long as you can achieve your desired range, although positioning to avoid valve/valve or valve/piston interference on solenoid failure would be desirable if they have a wide control range.

I understand about cam timing. I’m trying to figure out what is the point of re-marking the crank pulley more accurately? Is it just for the benefit of when using the timing light to get a more accurate result?

Yes, it's to verify the commanded ignition timing is the delivered ignition timing.

Should I also be re-fitting the timing belt based on the new mark if it’s different enough to be on a different tooth of the timing gear?

I’ve figured this out. I believe the answer is yes if the mark is off by a whole tooth then you probably should move the belt but the mark on the belt gear really shouldn’t be off by a whole tooth unless some extreme changes or errors have been made. The mark on pulley being updated is mainly for the benefit of having your timing actually be what you think it is.