Valve stem seals on 300 tdi

Anyone ever done valve stem seals on a 300tdi with the head still on .

I have a valve spring tool Overhead Valve Spring Compressor OHV Sealey VS160 Tool NEW GO NEXTDAY JUST £4.99 | eBay

just need to make sure the piston at TDC is close enough to the valve ..

Reading the advert its to be used with a compressed air adaptor to hold the valves shut...

usually you would , but thats easier on a petrol screwing into the spark plug holes , if needs be I will take oout the injectors and thread some appriately thick rope in and then use the piston to compress it against the head/valves .. Done it that way on a lot of other cars no problems .

I know the gap between piston and valve is small but how small ??

I will be doing it next week so I'll post pics anyway ..

The piston protrudes past the deck of the block also the combustion chamber is in the piston not the head so if you can get the piston at tdc for the valve stem seals you are changing in theory you should be ok.

Thank you