I heard opinion, that forged pistons cause the engine to be more noisy because of wider piston to wall clearances. Cast piston allows to cylinder wall clearance to be set closer, and, therefore, a quieter engine with less piston slap. Question is: Who of you guys, riding forged wiseco pistons ,have ever noticed engine more noisy than before conversion???

Lukas

I could be wrong but I thought that the forged pistons allowed closer tolerances because they don't expand as much from hot to cold. I heard they take longer to warm up than the cast pistons.

Someone with engine building experience can answer this one better. I've got Kieth Black forged pistons in mine on the recomendation of the shop that did the machining on my bores.

Picked up my Wiseco's from my dealer today and in the box it states clearance should be set to .002 -.0025 That's pretty tight if ya ask me.

I heard opinion, that forged pistons cause the engine to be more noisy because of wider piston to wall clearances. Cast piston allows to cylinder wall clearance to be set closer, and, therefore, a quieter engine with less piston slap. Question is: Who of you guys, riding forged wiseco pistons ,have ever noticed engine more noisy than before conversion???

Lukas


With the noise everyones pipes make, it's a miracle one can hear anything on their motor.

I used the wiseco's and I didn't hear any difference.

From everything I have heard is that forged pistons need to be set up with a little more clearance than cast pistons.

I was told by Justin at NRHS that they use a .003" piston to bore clearance on there Hurricane forged pistons and use .0015" on cast pistons.

It would be highly unlikely to get piston slap with a .003" clearance.

I have done alot of motors of all types and the forged pistons were always setup on closer tolerences. Cast pistons expand more than forged. I always go with the forged pistons.

OK guys we have a few points here...

Hypereutectic cast pistons, which are the only cast material that is used in later model HD's... expand LESS than Forged pistons..

Typically a stock hyper piston on a HD can be set as close as 0.0008" ... yes that's correct LESS than 1 thou

a forged piston expands more than a hypereutectic cast and will typically require around 0.0025" - 0.0035" depending on application.

Forged pistons tend to make more noise than a cast piston and I've personally run Stock, Wiseco forged and Beull cast in my personal sporty and siilar pistons in many customer bikes..

Cars have similar set ups .... most modern vehicles have hypereutectic cast pistons and are set up around 0.001" clearance..

Forged pistons in cars can be up to 0.008" depending on materials and application...

Diesel engines I've had forged piston clearance up to 0.013"


A forged piston is typically a stronger piston than a cast one and is usually better in a race application where max power and pushin the edge is more likely to occur...they handle detonation better



Just as a note, I also teflon coat my forged Wisecos which helps with the rear of the front cylinder which tends to have oiling problems in performance applications..

Well here we go again, different metal expand differently. Was talking about old cast vs forged, wasn't touching the hypereutectic pistons which you can indeed run tighter. We used a forged 4032 high silicon aluminum piston which you can run much tighter. Like everything else there are many ways to build a motor.

Yeah Doc....

The problem is, is that this is a sporty forum and if I start talking about old style cast like we used ta use in cars (which typically was around 0.0025" - 0.003") it's just gonna cause more confusion..

We start goin to old flatheads and we're in whole different ball game again... I've just sleeved a set of UL1200 barrels and am fitting cast car pistons, which I've teflon coated to help... the clearance on them was machined at around 0.0035" and I'm not sure exactly how we're gonna go in there...... I'm taking and educated/experienced guess..... I'll run it, then pull the heads and barrels off and have a look.... If I need a bit more I'll just take a lick more out... I'm hopin the teflon will give me just a touch more margin to play with

pics of the "U" will be posted in the near future , right stevo ?

when it's done .................................................. ................................................. .................................................. ..............................................


could be a while as the custoner has a few things in line before it

OK guys.....
I've go me some 04 XB heads from Barry1967 ported by J.E.T. Now I need to change my 1200 dished conversion pistons cos I will have a very low compression if I keep them (My Vincent runs just fine with 7:1, but then it only makes 28 ponies at the crankshaft).

So..do I get Forged Wiseco flat tops or KB cast flat tops? The guys at JET don't like the KB pistons...so it looks like Wiseco. I have no problem with that, I used some Wisco's to take my old XS2 to 750cc..BUT they are more expensive than the KB's.

I'm thinking the KB's right now.

So what is the recommendation? Stevo?

Thanks

Whiffi

G'day Whiff

Nothin wrong with either...

In your temps over there the KB's are maybe better if ya gonna be doin a fair bit of stop/start or short runs . The Hypereutectic piston is the same material as stock and can be set up real close

If ya gonna do a fair bit of draggin or runnin REAL hard with close to too much advance or Nitrous then maybe the Wisecos

The KB's NEED the ring gap set up as per their specs other than that I havn't heard of any probs with them...

I often run Wiseos here because due to our main wiseco importer I can get them waaaaay cheaper than most other pistons..... and they have deep valve pockets.
Although I still teflon coat 'em most times

Either way I would go to 0.005" - 0.010" over what ya got to get the clearance right and clean the bore up..Trying to match pistons to an existing bore is too much of a compromise and a lucky dip.

Cheers Stevo. KB's seem the way to go. I'll not be draggin it or running Nitro. I have a set of 883 cylinders I'll get bored for the new pistons, and paint them black at the same time to match the heads.

Thanks again

Whiff

OK .. it should go without saying Whiff

but this is more for others reading this thread..

Make sure they are done in torque plates by someone who knows what they're doin..

Do traffic light drags count??? :frownthre
I may just get the Wisecos anyway.....

One last thing that I've seen (but can't find anywhere) is that the 04 heads use different bolt sizes or spacings on the head mounts??

Do I need to go buy some bolts (if so what size) or will grinding out the existing head mounts suffice?

Had to ask cos i'm too lazy to measure it in close to zero wet weather.... :eek: Also UNF/UNC are hard to find in auto shops in the UK on a Sat afternoon (metric only easy to get nowadays).

Thanks

Whiff