All the tubes i've put in have been tough! They are a press fit and I put a 7/16" open end wrench right above the ring then very carefully use my air hammer on the wrench to rattle it down in the block. Also, there is usually a short piece that goes in first, about 5" long, that keeps the dipstick from flopping around inside the block and getting snagged by the crank. I'm had to file down the flange on that one too to get it to go down inside the hole. It usually goes down inside about 1 1/2", then bottoms out, then the top side tube goes in next. Hope this helps.