Do forged rotating assemblies "rattle" on cold startup?
Thread Starter
Burning Brakes
Joined: Sep 2009
Posts: 1,239
Likes: 2
From: Naples FL
St. Jude Donor '12
Do forged rotating assemblies "rattle" on cold startup?
Going to look at an LT-1 with forged pistons. I understand they rattle a bit on startup, a diesel-like piston slap noise. How much rattle should I expect?
I have a Suzuki Quad with forged piston, and it rattles pretty loudly, but I'm not that experienced with forged assemblies in car motors.
Any thoughts?
I have a Suzuki Quad with forged piston, and it rattles pretty loudly, but I'm not that experienced with forged assemblies in car motors.
Any thoughts?
Last edited by Coach62; Jun 17, 2012 at 07:46 PM.
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
Ever hear a diesel?
That rattle is from the super strong forged parts that have to have a little more clearence to operate and not seize. The parts are stronger so the rattle is not harmful...just annoying.
There was a LOT of complaining about later yr c4s and later engines that had a cold rattle that was written off by GM as piston slap when cold. As the engine warms and tolerences come into spec, the noises fade.. Forged rotating assys have this as a downside...so its something for a builder to consider. The standard hyper-type piston is tighter but not as able to take extreme stresses of severe detonation or forced induction...which generates detonation.
That rattle is from the super strong forged parts that have to have a little more clearence to operate and not seize. The parts are stronger so the rattle is not harmful...just annoying.
There was a LOT of complaining about later yr c4s and later engines that had a cold rattle that was written off by GM as piston slap when cold. As the engine warms and tolerences come into spec, the noises fade.. Forged rotating assys have this as a downside...so its something for a builder to consider. The standard hyper-type piston is tighter but not as able to take extreme stresses of severe detonation or forced induction...which generates detonation.
Race Director
Joined: Jan 2012
Posts: 17,062
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From: United States
Mine doesn't rattle. Suppoedly the SRP pistons are made of a different material than the companies JE pistons. Builder should recommend pistons for your power levl. Hypercutectics are a step up from cast and are pretty strong and can be set up tighter, to keep it quieter. But, then again, what is quiet on the C4?
Race Director
Joined: Sep 2001
Posts: 14,674
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From: NEwhere Ohio
dont dare forget also that the 'looser' tolerances of forged parts also causes more oil consumption.
THough all in all, Id rather have the forged parts in there. Esp. with my boosted setup. (which Im running just the stock cast pistons in there, w/ lowered CR down to 9.7:1 and meth.water inj. as a safety).
THough all in all, Id rather have the forged parts in there. Esp. with my boosted setup. (which Im running just the stock cast pistons in there, w/ lowered CR down to 9.7:1 and meth.water inj. as a safety).
