No need-- - - -if a few bubbles are in the line, they will compress and give a correct pressure reading. Don't be surprised if a 216 has little to no oil pressure at hot idle. Spray-oil engines can run with 15 PSI or less oil pressure at hot idle, and even less is not uncommon. 235 full pressure engines will have quite a bit more, but one with a lot of miles and some rod bearing wear will also be lower on pressure than most people are comfortable seeing.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!