Back when I was still in the Marines at Yuma, the old staff sargeant who ran the hobby shop garage had me cleaning out the bores of the oil passages on my just machined 292 with .30 cal rifle brushes on a ramrod using military bore cleaner. I chased it down with a lot of WD40. That engine ran for 25 years.

I/I #4101
'71 GMC Jimmy 350, sm465, np205,3.73 posi.
'68 C/10 Stepside 292 (.030 over) Offy Intake, 500 CFM AFB,Clif headers, sm465, 3.73 posi.
'67 K/10 454 project.
'72 K/5 rolling frame project.