69gs400 oil gauge flicker and rocker noise

going on freeway after far was warmed up from driving 15miles on a 90degree day i florred it to finally feel the power of a newly purchased 69gs400. after the oil guage strted flickering slightly at 60psi and i started to hear the rockers i beleive wich i 1st thought was a exhaust leak. about 1mile of drivin it got louder so i pulled over and as i was about to stop idle felt off and started to shake.after 10mins to look under hood. i found nothing leakin and everything intack including oil gauge line. i started car and idle felt rough still for 1 blick then leveled out and rocker noise stoped completly. so i drove home and in park i reved back to 3k rpms simulating the 70mph i was going and oil started to flicker at 60psi again bt no rocker noise yet. did this 3timea and parked in garage. any ideas. milea unkown. unkown age of oil pump. no oil plate added ad ive only owned the gs for 3 months. 2nd timea florring it bt 1st time frok only 20mph. other time i was alreay on freeway going 65mph

what brand of oil filter are you using?

what kind of oil?

have you checked the oil for metal / bearing material or had it analyzed?

when was the last time the engine got a rebuild and do you have any idea what work was done?

it would be a bad idea to run the engine until you verify that you're not tearing a bearing up.

there might also be something in the bottom of the oil pan interfering with the pickup or the pickup might be loose or you might be pulling air from someplace else.

remember, if that's factory original, that's a +45 year old engine. pretty much anything could be going wrong with it. the timing gears are plastic and they deteriorate after this long.

might be time to put the 400ci + trans in plastic wrap storage and build a 455ci.

darn the luck.