I wish I could talk to a lot of the people that engineered parts for these old Chev's to know what they were thinking.
I have done extensive research on 235 hydraulic lifters and have found that every time people, including me, have high speed lifter noise it is from aftermarket lifters with a vent hole in the push rod seat. In all of these cases notching the push rods cured the problem.
I am working with a test engine right now that is not drilled for hydraulic, and I am running hydraulics's in it.
If this works out, as it seems so far in my test engine, I will be able to install hydraulic lifters in Chev's as early as 1929.
