merlin24

iTrader: (1)

Piston to bore clearance on Wiseco pistons is generally around 0.003" and can be increased slightly for track day cars etc.
If the "piston slap" does not decrease as the engine temp comes up,then would imagine it would be a problem with the off-set orientation or a problem with the gudgeon pin bosses on the pistons.

Mick

dazdavies

iTrader: (22)

Not all Pistons have offset pins. Might be worth finding out what pistons the build in question has

bigarf

iTrader: (67)

the pistons that have been used are wisecos, what is meant exactly about the offset that could make the pistons noisy.

dazdavies

iTrader: (22)

Ok then that might shed a little light on it.
With Wiseco and some other brands of pistons the gundgeon pin is slightly off centre. This means that the piston has to be installed in a certain direction.
Here is a pic taken from one of my builds using Wiseco's. The Piston not only had a sticker on it stating the offset issue but you'll also see the face of the piston has a mark on it indicating which way should be pointing towards the front of the engine. Your builder may have got this wrong

bigarf

iTrader: (67)

ar thats what it means then,to be honest i dont know realy what direction i should take as my engine builder did say that if i wanted an engine with no piston slap at all that he would build me one but the engine would have tighter tollerances and as ime wanting an engine that will handle a lot of power and boost would that be a bad route to take.as it has been mentioned earlier when your wanting to run big power the looser the better.i think ide rather have an engine that had some piston slap but will handle big power than an engine that was quiet that and could let go any time.

dazdavies

iTrader: (22)

With a properly built engine the Piston slap should go away when the engine gets warmer.
3-3.5 thou sounds about right for clearance wise but it should only be audibly noticeable when the engine is cold

bigarf

iTrader: (67)

well by the looks of things the engine is going to have to be taken apart again anyway to cure the oil breathing problem which he says he will do no problem so all these things will have to be checked again when it does i suppose.but for now i just need the car on the road for a while till i can get my old runabout up and running again.this will get sorted out for sure as we had a good talk at the weekend and he gave me his word that he would sort it so until its been in again and rebuilt ile just have to enjoy it as is.

dazdavies

iTrader: (22)

Well atleast the builder is doing the right thing without a quibble.
That seems a rare thing these days.

BlooSooby

I've got forged CP pistons in my EJ257 and they DON'T have an offset.

When the engine is stone cold you can barely hear some piston slap, when the engine is at normal operating temp it's quiet. However, if you get the engine to operating temp and then stop for about an hour, when you restart the engine the slap is quite obvious, this is because the piston and bores quickly cool to the jacket temperature but the oil stays warm and less viscous than when cold.

Obviously the more viscous the oil, the quieter the engine!

Mus

iTrader: (2)

thats sad man who bulit the engine?and do u have any warranty with it.?

bigarf

iTrader: (67)

yeah things were a bit tense at first with me not being able to contact him and so on but now i have had chance to talk properly to him and sort everything out he doesnt seem a bad bloke at all.

BlooSooby

That's good, it seems like it'll get sorted now.

As a point of interest, my builder built my engine with 0.0025" clearance, he says that clearance is specifiic to CP pistons and is the tightest clearance he uses, so your clearance seems good.

If you give your engine a good caning and then pull up can you still hear the piston slap on tickover?

evander

iTrader: (1)

I have CP pistons in my EJ257, on start up there is noticeable slap, go for a drive and once warm its all but gone. If you let it idle for 10 - 15 mins the slap will come back to a lesser degree but go for a short drive and its gone again, all this shows is the pistons swelling with heat.

I wouldnt worry about the slap unless its extreme, I would be more concerned about the oil consumption though, how many mls per Ltr of oil? You could consider a return from you catch can to the sump so you would no longer need to monitor the catch can and just top up as required.

bigarf

iTrader: (67)

its not so much on tickover its around 1500 to 2000 rpm were i can here it, after a realy good thrashing the noise is still there but not half a bad as on cold start up.not that i thrash the car all the time that is

BlooSooby

Like Evander says, i'd be more concerned about oil consumption.

I went to the carwash today, after 20 minutes washing the car I drove out and parked up to chamois the water off but left the engine ticking over........it was sounding like a freakin' Massey Ferguson for a few minutes!!

It is a bit unnerving at first but it's the performance that matters mate

silent running

Well all I can say is that Wiseco say they use offset pins because that is the OE way and leads to quieter operation. If you get them the wrong way round it will be noisy, simple as that.

bigarf

iTrader: (67)

well all i can say is if thats the quietist they do then ide hate to hear the noisy ones.

ZEN Performance

I see a lot of opinions, but only a few replies that come from actual experience. Aftermarket forged pistons DO make more noise, even when hot they will make a noticeable noise that will range from a barely apparent ticking to a constant diesel like rattle. Different piston designs will result in different levels of noise though and some are better than others. It is also normal to use a bit of oil in the first few hundred miles of running as the rings bed in, but that should settle down.

If you are genuinely concerned, then take the car to an independent person/outfit with experience of building Subaru engines (forged pistons in an iron block EVO engine sound completely different for instance). They will soon tell you if the sound is out of the ordinary.

silent running

Well I've not heard the ones in question, so I can't say. All I'm doing is quoting something that Wiseco make clear mention of in their fitting instructions.

DJ_Jon

iTrader: (7)

I've got wiesco pistons & rods, mine are a bit noisy when cold, but it settles down when warm. I've used half a litre of oil in the last 600 miles.