its worth a try. i had some intermittant rattles and ticks coming from my lifters. i used the famed "snake oil" (engine oil flush) which supprisingly worked a treat. flushed it then added some lifter free additive with fresh oil. seemed to stop the problem straight away. if your not keen on the oil flush additives there is a product called Auto RX i think. a little harder to come by but i think you can order it from the states. it apparently works a lot slower so not to cause damage to your seals ect. your other option is using a high detergent desiel oil. we have a few trucks and tractors and on occasion about 500 km before i next service i dump the oil, fill up with Devlac and then after 500km dump that and change the filter. i'd say if they are making a lot of noise or you think they might be really clogged you may have to pull them out and service them. its worth a trying the other things first as they are a lot cheaper/easier than stripping down you engine. just a few suggestions, as usual i take no responsibility for any problems or damage you may cause if trying any of these methods rah rah rah.... hope it helps. there are probably some other people on this site which would have a much better understanding then me. good luck
My engine is only runing on 5 cylinders, Did a compression check on the cylinder that is missing and it had 30psi... Hopefully its something like a sticky lifter ( it makes a tiking noise under tapet cover) and not a burnt valve..