George D

A good machine shop with experience with Alusil like you mentioned.

http://www.sunnen.com/NewsDetails.aspx?NewsID=11

You'll have a nice setup. Most of the 2.8 stroked motors use the factory Alusil bores with excellent reliability. Wossner will match their pistons/rings with compatibility without coatings, which I think is vastly superior vs coating a material that's NOT designed for Alusil. I've known 2.8 stroked motors with over 100K of use with same reliability as the factory 2.5 turbo blocks when running well with good tuning and sane boost levels. You'll save a few bucks and have a proven motor.


QUOTE=blade7;12030084]I have spoken to him about pistons and liners but he uses Capricorn engineering and they don't seem to be taking on new customers. I'd like to use plated bores like George mentioned but that's not an option in the UK. The 2.7 block I have has unmarked bores, I'm taking it to be checked for ovality/taper and if it's OK I'll just have it cleaned up with the Sunnen pads and paste and use it with a set of Wossners.[/QUOTE]

blade7

I spoke to the local Sunnen rep and he gave me the names of some companies nearby that have their kit. TBH if the block needs more than a light hone and freshen up with the paste I'll have to use liners.

PF

What about using Mahle motorsport pistons? I mean that is what came stock and they work great with the alusil bores.
Lindsey can get the size you need last I checked.

Regards
Peder

KSira

Was that JE with cylinder liners? Did he use JE rings? Not sure I understand how pistons can affect rings failing after 18k, unless they carved up the cylinder walls. The JEs sounds awful at start up and keep rattling until engine load is applied. My car is so loud anyway and is mostly a track car, so it is not a big problem for me. They are heavy also, so I would buy Wössner if delivery time and price where not an issue. For me the short delivery time with Chris White having a set of JE piston on the shelf made the difference.


Edit: Was it worn ringlands in the pistons that caused blow by?

blade7

Lindsey only have the 2.5 Mahle pistons on their site and they seem to be 30% more than the Wossners.
Are your JE's 2618 KSira , the clearance and noise wouldn't be acceptable on my road car and as I'd never run more than 18 lbs boost I want to use 4032 pistons.
I'll probably fit an M-Tune, a 3 inch downpipe and the turbo I have to my 2.5 and iron out any bugs before switching to the 3.0, it would be nice to have it built up on the stand ready to fit though.

333pg333

My builder could get you custom Mahles to your or his design...but they'll be more expensive than the JE or Wossners.

KSira

Not sure, bought them from Chis White. Is there any way to tell the difference?

Thom

I am having Mahle pistons custom-made. They are more expensive than Wössners, but they will most likely expand less thus require much less than the 0.08mm clearance often recommended for Wössner pistons, which is the wear limit mentioned in the FSM.

blade7

Are the custom Mahle pistons coming from Europe or the US ? Wossners from the US wont leave much change from $1400 US by the time they're delivered and as my 3.0 wont run high boost or revs I wonder if it's worth spending more ? I'm a bit twitchy about running less than 0.08mm clearance on a 3.0 block too.

blade7

How much clearance was specified ? AFAIK the 2618 pistons are stronger but expand more, for a car that's used hard they're probably the right choice.

Voith

Andial ferrostan mahle 104.5 turbo pistons were made in US.

George D

Mahle pistons would be fine. They are just hard to get in specific sizes, etc. Wossner is as good as Mahle, and they will work with your exact needs.

George D

No, NiCom block. Pulled the head because of excessive smoke and bad compression numbers. The pistons and rings were from JE and the motor was built/assembled by a reputable builder. The clearance mandate using JE 2608 pistons cause slap until the pistons expand from heat. You could see the wear on the skirts and you could move the pistons back and fourth from when TDC in the bore. We assume the slap caused pre-mature wear on the rings, and caused some bore gouging. Sean Martinez helped Jeff rebuild the motor at his house in Tucson with our help. Sean has been building motors since he was a kid, and has a MS in Mechanical Engineering. I know of builders who have successfully used JE pistons these motors. Just have no idea about longevity. Just sharing my experience, no issue with JE. My 3.0 motor was built by Garrity at Motorsports. He ordered six sets of JE pistons, one for my car, and five for 911 Turbo engines. JE knew these motors were all NiCom bores, and my motor and thankfully only one of the 911 motors were built and run on the dyno. JE sent Garrity the wrong ring material and when bore scoped, there was bore damage. He sued JE, as they wouldn't fix the issue and Garrity warranted my motor using a new 968 Nicom block and Wossner pistons. Motor has been running fine.

George D

Piston to Bore Clearance: Wossner pistons already have the recommended clearance built in. Skirt diameter is smaller than the recommended bore size (see sizing on box). Some applications: Nitrous, supercharged, turbo, and cold water marine engines may need more than the recommended clearance.

Wossner pistons are measured 90 degrees from the pin axis at the widest point on the piston skirt.

Adding additional clearance then recommended may create extra engine noise (piston slap) upon start up and cold running. This can cause damage to the pistons and/or cylinder.

Application Top Ring Gap (Min) 2nd Ring Gap (Min) Oil Ring Rail
N/A Street .004" x Bore .005" x Bore Min .015"
N/A Race .0045" x Bore .0055" x Bore Min .015"
Turbo/Supercharged .006" x Bore .006" x Bore Min .015"
Dirt/ATV/Snow .004" x Bore .005" x Bore Min .015"
Nitrous .007" x Bore .0065" x Bore Min .015"
Circle Track/Drag Race .0055" x Bore .006"x Bore Min .015"

Wossner Pistons utilizes both 4032 and 2618 Aluminum alloys for our pistons as well as 4340 steel alloy for our rods.

I recommend running 4032 pistons in both race and street 951 motors. We can't boost these motors with reliability past 23 psi or so in track conditions, and the 4032 forged Mahle and Wossner units will easily handle these conditions.

Cut/Paste:

I have seen alot of misinformation about the differences and which is best to use for what application. Some forums have members that believe the 2618 is the only choice for any FI, and 4032 is for N/a; which is not close to the truth.

Basically in a nut shell, 4032 has higher silicon content which makes it harder and expands less under heat-meaning you can run tighter piston to wall clearances, better wear and less noise, longer life. However, the tensile strength is not as strong as 2618 which means 2618 can handle detonation better. This is where the misinformation comes from. The reality is that a 4032 piston is actually very strong and will hold up to detonation much better than a stock cast piston. They are good for turbo applications, but if max power is what you are after, then 2618 is probably the better choice. So where is the point that you should choose 2618 over 4032? That is debated everywhere, but with about a 12% less tensile strength, it is likely only around 12% less power than 2618. So, If a 2618 piston is rated at 1200hp, the 4032 should be able to hold 1000 hp with the same effectiveness. But no matter what, any piston has the chance to melt down/crack/break apart with a bad tune.

Long post, but good information

KSira

Minimum clearance where set to 0.005". Mine ended up with slightly bigger clearance