340 head bolts are 1/2" thread with shank at .450" . do anyone make a 340 head stud for the 2 long ones necked down, so the oil to the rockers is not restricted?
checked my old 5/8" shaft HS rockers and the needle ends digging in to the aluminum and there is no oil hole to the roller tip. .500" studs at the 2 longs did not help. big blocks also oil up to the rockers thru 2 head fastener holes right big block guys
hmm....it would probably be easier if the heads were off.. to pickup one of the Long shank ball end carbide cutters.. and carve an oiling groove in that bolt hole.. so a full sized bolt cannot restrict the flow.. rather than reducing the diameter of the bolt.. i seem to recall that the rocker shafts had an oversized hole also to allow oil flow.. with a hooked wire.. you can remove the oil pump drive shaft from the block usually.. and use a piece of hex rod.. or grind the gear the gear teeth off an oil intermediate shaft even press the gear off an old one and weld some material to the slotted end so you can make an oil pump priming tool.. even removing the spark plugs.. with the distributor installed so you can crank the engine to check for oil flow from your rocker arm oil port or from the rocker shaft.the passage you need to see is on the upper right side of this image.. move the slider to view it..