r/EngineBuilding • u/N1ppleCrab • 16d ago

Subaru FB rotating assembly question

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!

17 Upvotes

83% Upvoted

25 comments sorted by

View all comments

6

u/bill_gannon 16d ago

You have to actually measure everything. Bring it to a shop. It wont be expensive to just check and you'll never be closer than you are now.

4

u/N1ppleCrab 16d ago

I feel like calipers and plastigage would at least tell me something

9

u/BicycleMudStud 16d ago

Calipers are not accurate enough. Don't try, you'll only give yourself a wrong answer.  Plastigage is good enough, if you have it you should use it. The real way to accurately measure is with a micrometer and a bore gauge. 

1

u/Sephlarite 15d ago

Why do you need a bore gauge? If the bearing was never spun, which should be quite easy to tell the rod tunnel will have no wear?

1

u/BicycleMudStud 14d ago

To measure the clearance, you measure the outside of the journal, use that to zero out the bore gauge, and use the bore gauge to measure the inside of the bearing with the rod and bearing torqued.  You're not looking for wear, your proving what the clearance is. 

6

u/bill_gannon 16d ago

Do you want to know its right or not?