Having owned a K series there are other components that require changing at the same time as the timing belt but I have seen a cheeky short cut to changing a belt. Not possible with a K series as from memory to remove the lower cover the crank pulley has to come off.
Cut the belt lengthwise down the centre with a Stanley knife then pull off the forward half. Fit the new belt then cut off the remaining half of the old belt.
A procedure only for the very brave.
You can still do that on a K. You cut it in half with the engine running and top cover removed. Still needs the crank pulley removing though so no use to the OP as he doesn't know if the keyway has been shimmed. I've done it that way on cars when I'm changing the belt due to age but know the tensioners/anything else on the belt you might want to change haven't been on for many miles. Got to be careful to keep your Stanley knife held straight though.
I used one of these https://www.eurocarparts.com/p/laser-camshaft-locking-tool-rover-k16-LAS2626 Cheap enough and every little bit of help for a first timer is good. I used the 'white dot' and the 'in gear with the foot brake applied' tricks as well. Take your time plus check and recheck using photographs as a start reference.
R.I.P. SLR No.27.
I suspect the safest answer would be to re-time regardless. Which fills me with a degree of dread :D Not least of which because the guys who did the engine work (and later the chaps at Emerald) did such a brilliant job of it that I don't want to mess that up, and I believe cam timing is key.
Still, what could possibly go wrong! (I'm seeing this particular job as my biggest headache).
If I get chance this weekend I'll start to take it apart and will take photos. (Though think the in theory easier task of sorting my wheels/rear ARB drop links will likely come first).
You could always do what I did - fit the belt and let someone else time it in! I was advise to retard one cam and advance the other 10 degrees for a safety margin.
DVA power has a write up how to do it and how to make the dial gauge brackets.
I must have been lucky - I never noticed any slop at all in the crank/pulley fit.
I hope I would of if there was -day job is designing, building, testing, improving and fault-finding where accuracy of fit is rather important!
I'll certainly wear my specs next time!
Is that the purpose of the cam locking tool - get it nicely in place, lock the flywheel firmly in place so that when you fit the new belt, it locates the bottom pulley as that's the (slightly) free part?
Bricol - Yours may not have any depending on what's been done. You could have a crank and pulley that have been accurately keywayed during a (non Rover) engine build.
The cam locking tool doesn't solve this issue for you I'm afraid. I have a K-series in the row of engines that are in my garage at the moment. I'll make a quick video tomorrow to show how much movement there is.
I changed my 1.6 K belt + accessories three times during ownership. It is straight forward.
Set TDC, use the ally locking block for the pulleys. Broad blade screwdriver firmly inserted in ring gear through off side hole. The rest as required.
Works every time with no problem. Honest!
You don't time the K-series with No. 1 at TDC. The timing marks are set for 90 Deg before TDC. Also as above, if you use this method for assembly with an unmodified crank/pulley your cam timing is not accurate.
Edit: Actually this looks to have gone round once so will leave you to follow whichever advice you prefer OP. Best of luck and hope it's all fine after being laid up
SV VVC 170 - 170.4 bhp @ 7100 rpm - 142.4 ft.lb. @ 4900 rpm