So in my recent valve stem seal replacement task I had to use a tool to be able to remove the valve springs whilst still on the Jeep. I purchased a Sealey OHV tool and thought all would be good (looked similar to ones I had see used on US forum sites) however, in use this did not work out as planned and I actually damaged one of the seals trying to recompress the spring (lucky I had a spare). The problem seemed that there was not enough compression available to get the keepers in and out and the legs of the tool fouled with the stem seal. So in a panic I rang a couple of friends (mechanics) and asked if they had a different tool for the job. Luckily one said he had one but it was a genuine Mercedes V8 engine tool and he was unsure if it would work for me. I grabbed it and with a small amount of modification (attachment to the head) it worked perfectly and the valve springs were easily removed. It was so good I've copied it for any possible future requirements.
Here is the tool,



Basically the rocker is removed and the Tee piece is screwed in the bolt hole opposite the valve, the tool attachment section clips over this and then by simply placing the cap of the main piece over the valve and pulling down on the lever exposes the keepers perfectly. A basic magnetic tool helps pick up the keepers. Oh and I have an air fitting to fit into the sparkplug hole (with valve) that pressurises the cylinder.
So if anyone needs a loan its there to be used, would probably work on a multitude of engines that have a similar setup