Forged engine: Newbie question

[Mr-C]

Hi everyone,

 

I just got back my car which has a freshly rebuild fully forged engine and in running the car the last 2 days I've noticed the following:

 

1 - Some noise from the piston (slap/knock type of sound). During cold start up its more pronounced then once its running at operating temp.

 

2 - A little bit of white/blue smoke coming out the exhaust every now and then when starting up the car.This seems to only happen when the car has ran a while and has sit for 5-10min...so far on cold start everything seems fine.

 

My buddy who's a Subaru and rally team mechanic was the person to perform the install and has advised me this is normal. Because of the forged pistons, the pistons sit "loser" in the cylinder causing the sound and some oil to pass.

 

I don't think my buddy has any reason to lie to me, he's installed a bunch forged engines now and says its perfectly normal. However seeing I'm new to forged engines I'm looking to those who have experience to confirm his statement and relieve my concerns.

 

Thanks,

[Max Capacity]

1. that's normal for forged pistons. Get used to it.

 

2. most likely normal condensation be burned off in he exhaust system.

 

Lot's of cars emit a little white vapor on start up sometimes, depends on dew point and temp.

 

You should spend more time on here, read the sticky's and learn a lot.

 

Keep an close eye on oil consumption and always keep it topped off. a little over is better then not enough oil.

[Mr-C]

Thanks for the feedback,

 

I'm not a novice by any means when it comes to Subaru's....I've been an owner for the past 15yrs.

 

I never heard or read about this before, more than likely because I've never had or known someone with a forged engine.....I would have expected my buddy to enlighten me at the time we were discussing my options, I guess it didn't come to mind.

 

That said, I've already started doing a bunch of research which has helped alleviate my concerns, I'll take this away as a good learning opportunity and keep both eyes on my oil level & consumption.

 

 

 

Cheers!!

[d22597]

Here is a sticky that provides a good overview.

 

http://legacygt.com/forums/showthread.php/those-you-considering-aftermarket-forged-pistons-130635.html?t=130635

[Mr-C]

Here is a sticky that provides a good overview.

 

http://legacygt.com/forums/showthread.php/those-you-considering-aftermarket-forged-pistons-130635.html?t=130635

 

 

Thanks for sharing.....some good info!!!

[Max Capacity]

Please keep us updated on how the engine holds up over time.

 

My stock ej257 has over 101,000 miles and is as quiet as when I first started it.

 

Have heard Forged don't last well in a DD...?

[Mr-C]

Will do!!

[Kcdrift]

Hi everyone,

 

I just got back my car which has a freshly rebuild fully forged engine and in running the car the last 2 days I've noticed the following:

 

1 - Some noise from the piston (slap/knock type of sound). During cold start up its more pronounced then once its running at operating temp.

 

2 - A little bit of white/blue smoke coming out the exhaust every now and then when starting up the car.This seems to only happen when the car has ran a while and has sit for 5-10min...so far on cold start everything seems fine.

 

My buddy who's a Subaru and rally team mechanic was the person to perform the install and has advised me this is normal. Because of the forged pistons, the pistons sit "loser" in the cylinder causing the sound and some oil to pass.

 

I don't think my buddy has any reason to lie to me, he's installed a bunch forged engines now and says its perfectly normal. However seeing I'm new to forged engines I'm looking to those who have experience to confirm his statement and relieve my concerns.

 

Thanks,

 

 

Yeah same as the above comments really.

 

1. That noise is piston slap. Forged pistons are run with larger tolerances because the piston will expand as it gets hotter. The expansion is a known property of the forged piston. The extra tolerance means it will kinda run in the cylinder until it warms up.

2. The exhaust you see is probably normal but forged pistons being smaller in size on cold start ups allow more oil to pass the rings until it begins to warm up and fill the cylinder properly.

 

Your concerns are normal and these are common things that occur on a built block with forged internals.