VandykeT/A

We just got the 408 together and running but at steady throttle like 2k it has a piston slap sound. It's all forged (wiseco pistons). It holds excellent oil pressure fires right up oil looks good after first change it just has that piston slap sound very faintly. Clearances are .0025. It does this even warmed as is only really at a steady throttle say 2k above that you can't hear it. Is this just the nature of it or should I be panicking. I know this is impossible to know anything about in a thread just curious if anybody else had noticed a light slapping with forged pistons. Engine has roughly 40 min run time.

TMTMTL

2618 alloy? you say warmed, but are you letting her warm up all the way? 2618 pistons can be noisey

just an incite, 2618 have less sillicone in them so they expand a lot more, so usually the clearences are bigger on that type of piston due to expansion. so at cooler temps you will hear them.

redtan

iTrader: (5)

What you're probably hearing are the lifters and/or valves. Piston slap goes away, valvetrain noise doesn't.

VandykeT/A

Honestly I'm just trying to talk myself out of it being a rod lol. Hopefully it's one of those.

VandykeT/A

Motor has over 30 miles on it and the noise hasn't changed everything else is fine. Let's hope it stays that way.

VandykeT/A

Ok it's got 60 miles on it and the noise does die down some when warm. It's like a hollow dieseling sound very faint. I honestly believe it's piston slap. Were gonna drop the oil pan and check everything. What's the odds a piston skirt could touch the counter weight on the crank? If pulling the oil pan reveals nothing should I be worried about it ?

89gtcs

Pretty unlikely - I'm assuming those clearances were checked during assembly? Do you remember what they were by any chance?

Does the noise change with RPM? How hot have you gotten the engine?

VandykeT/A

I'm confident that piston slap isn't the noise I'm hearing. I talked to the machine shop today and he said they were within a window of 4.0298 and 4.0302 so they're no way my piston to bore should be off. The oil pan was dropped and found nothing rubbing or hitting and the cylinders looked perfect but I can grab the rods and wiggle them side to side and hear the noise I get while it's running. The rod side clearance is .016 which is with in spec. We pulled all the rods and main caps and all the bearings look great. I'm assuming the noise is just something I'm going to have to live with.

01WS6/tamu

iTrader: (37)

forged pistons are noisy by their nature.