ok, so i'm putting together the new 383 and i went to check the piston-to-valve clearance using the modeling clay method when i noticed that the stock hydraulic lifters im reusing squashed down under the pressure of the valve springs as i turned through a cycle. now, since i only installed one head to do this test, i checked the other 8 lifters that i haven't yet installed and they are very firm and can't be compressed by just using a pushrod. all but one of the ones i did install can now easily be compressed with a pushrod. the plunger returns to normal after pressure is released so the springs inside the lifter seem to be working and everything else about them looks perfect. i'm just wondering, is this normal or does this mean my lifters are collapsing under the increased pressure of the double valve springs on my new heads? or is something else wrong here? will the lifters pump up to normal after the engine is started? i checked the lift with a dial indicator and it looks like im only getting about half the amount of lift that im supposed to have, except on one valve which appears correct, thats the one that didnt compress. i'm a bit confused...

 

you should be using checking springs and preferably a solid lifter

 

your lifters will all perform near the one that didn't compress when the engine is running. Hydraulic pressure keeps applied from your oiling system so that they can't collapse. You will bend valves or pushrods before you collapse a lifter most of the time if your engine is running.

 

so is this ok then for hydraulic lifters? should i not be concerned?

 

Its ok for hydraulic lifters to collapse when you're doing what you're doing. You should always use solid lifters for checking tolerances.

 

oh yeah i forgot that trick. thanks.