New Hydraulic lifters you are depending on machinist work from people who just don't give a damn. I haven't seen any sets that fit or worked as they should
Agree. I had to swap 7 out of 16 lifters on a resent small block build. Then 4 more fighting ticks at idle.
I tried many additives to no avail. But you may be able to buy Johnson's High Lift hydraulics. They get good reviews.
Hard part is shipping to the UK. Just a suggestion.