question about forged pistons
05-06-2011, 12:42 PM
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question about forged pistons
i have heard that they can cause your engine to have a loud ticking noise, even if you have excellent leakdown and compression with no oil consumption issues. can anyone confirm this?
05-06-2011, 07:38 PM
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forged metal is more dense than cast metal. So it expands more when heated.
This means forged pistons must run larger clearances (piston/wall) so that they have the room to expand when they get hot (and then create the tight seal).
So Forged pistons will sound "diesel-ish" when the engine is cold, as they clatter a bit due to that extra clearance. This can also cause blowby and excess oil consumption if you do alot of short trips that doesn't allow the engine and pistons to warm up fully.
All of those problems go away once the engine is fully warmed up though.
You should always compression/leakdown test a WARM motor, not a cold one.
This means forged pistons must run larger clearances (piston/wall) so that they have the room to expand when they get hot (and then create the tight seal).
So Forged pistons will sound "diesel-ish" when the engine is cold, as they clatter a bit due to that extra clearance. This can also cause blowby and excess oil consumption if you do alot of short trips that doesn't allow the engine and pistons to warm up fully.
All of those problems go away once the engine is fully warmed up though.
You should always compression/leakdown test a WARM motor, not a cold one.