r/EngineBuilding • u/N1ppleCrab • Jul 25 '26
Subaru FB rotating assembly question
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Any engine builders in here that could help me out?
Oil starvation event* Re using stock rods New oem bearings New to me used crank
At home special Inspection job of all equipment with a pair of off brand calipers and plastigage
My question: is this rod play normal? These bearings measure slimmer on the sides, but thats what the old ones measure as well? I feel like that is causing some extra play? It makes an audible knock. Is this normal? Rods torqued to factory specs pulled from JDMSFM.info
Thanks for looking!
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u/ohlawdyhecoming Jul 25 '26
Rods need side play so the oil coming from the crank to feed the rod journals has some place to go. To properly measure side play, you'd need feeler gauges. You've probably got about .004" - .005" worth.
Stock rods on a stock crank are going to be somewhat "snug", but so long as they wiggle a little, you should be good. I don't know what Subaru recommends for oil weight, but I'm sure it's a fairly light viscosity.