Lightweight Flywheel + Crank Pulley: Bearing Failures?
 

There has been discussion in various places around the internet, usually as a tangent from the original topic, about the possible hazards of running a lightweight flywheel and a lightweight crank pulley. The apparent issue is that running both will upset the balance of your crankshaft to the point where it will cause bearing failure.

I'm not a veteran Subaru guy, but according to the ones I've talked to, it's common knowledge that this is certainly the case on EJ motors. I've seen some eyebrows raise at the idea that this is the same on the FA20 as well.

So I would like to gather some raw data on the subject. Here is the thread that originally drew my attention to this potential issue: Cons to a lowered weight pulley set? The topic comes up on post #15.

I am very much interested in this discussion; thank you for bringing it up. I'm looking forward to seeing some real information!

Yes, I'm tired of the speculations and opinions. I've already put my stock crank pulley back on, just to be safe, so I'd really like to know if that was necessary or not.

I'm all ears to this considering I'm gonna do a lightweight pulley set soon...

Sub'd for info.

I've heard the lightweight crank+flywheel "possible rumor" as well

In for some facts.

I'm in for facts, have lightweight pulleys installed and am having a lightweight flywheel installed as we speak.

I've heard this is a no no on other platforms also. The light weight accessorie pullies are fine to use with a light weight flywheel but not a crank pully

The EJ series motors eat themselves apart just for fun. Not really a good comparison to ours.

We run all available lightweight pulleys, lightest weight flywheel, carbon drive shaft and wheels that are lighter than stock as well and have so since day one in our race car. It now has over 30K miles and shows no signs of slowing down. Car is boosted for most that time as well. Lightweight rotating components are absolutely fine as long as balanced. :)

Pulley with stock flywheel is fine as well. The flywheel is really the cats meow to me being as light as possible with this car. It revs so much faster, love it!

Thanks. I actually removed my post because I found the answer already....lol. But thanks for the quick response nonetheless.

Pretty much false it has anything to do with bearing failures on these flat 4s. There's not any evidence to support the theory than there is evidence to support those same cars with bearing failures probably also used spark plugs ;)

The EJ motors have bearings because there are so many terrible engine builders so the resulting drop in oil pressure causes bottom end failures. FA20s fail also because they have inadequate oil pressure to support higher power and RPM.

I have had more failures without than with and we've built probably over 700 EJ motors and the majority of those engine failures did not have a light weight pulley. My FA20 had failed twice without lightweight pulleys and never with but neither the failure nor the success had anything to do with the pulleys. It was 100% a result of fixing the actual issue which is the lack of adequate oil pressure to support the HP.

Run pulleys and lightweight flywheels without fear of bearing issues but you might have some idle issues :)

I have a lightweight crank pulley, and it's fine but I've been hearing some clacking noise. I don't know if I need to put the stock crank pulley back on and take it in....

I have had a lwcp, act prolite flywheel and aluminum driveshaft for 15,000+ miles now. I did have some idle dip issues which were fixed by raising idle to 900rpm. I tried out an ATI harmonic balancer and had more issues with that. :lol:

Flywheel chatter is normal with lightened flywheels.