Duke

Speak with shops working with older Mercedes as they also have Alusil blocks. Maybe you can get a recommendation that way.

Penguinracer

Sunnen make the AN30 lapping paste & felt pads. I emailed them today as their website suggests they do engine work rather than just sell the products.
With regard to clearances - if 0.08mm was good enough for Duke - it'll be fine for me!
Blade - thanks for those names - I had them in my spreadsheet but hadn't had any feedback on them.
I think our Stateside friends would find it difficult to appreciate how much of an abandoned orphan the 952 is in the UK from the modification perspective. It's just an unloved old Porsche worth scrape value "...you know...the one they made back in the '80's which looks like an RX7!"
Tim

blade7

Yes I had wondered about that.

blade7

I Looked at the S2 manual and if I read it right bottom size for group one pistons is 103.983mm and top size for the block is 104.015mm giving 0.032mm potential clearance, I think Dukes 0.08mm or around 0.003" in old money seems more like it for a tuned turbo. Was there any piston slap from cold Duke ?

Cheburator

Three points of call:

Sutton Rebore in Sutton - have done 4 928 blocks for me and friends. 3 of them are running strong, one is actually supercharged and putting down 500rwhp. One grenaded (mine) but it had no oil in it, while being flat out in 4th on the back straight of Snetterton...

Goznays in Essex - have done plenty of 944 engines, and know how to work alusil

EMC Motorsport - probably have forgotten more about the 944T than most have ever known. Kevin was involved with the original 944 Cup series. The last 944T they build won the CSSC "Future Classic" Series in 2010 with a novice driver. EMC would advocate cast iron dry liners/Nikasil via Capricorn and Arias pistons. Given that there is only one person in the UK who can actually map a Motronic car properly - Wayne Shofield of Chips Wizards, perhaps it makes sense to go with a sleeved bores engine, given the higher margin for error that it affords?

You can also get in touch with Hartech - but all they will do, is sell you a Nikasilled liner. A superb product, but not cheap either. You can go with that, or you can go cast iron... The pros and cons are well known...

One thing is becoming clear though - for a street car, with moderate performance and longevity in mind - alusil is still best from cost perspective. You want to boost it and thrash it - liners or nikasil plating is the safe and obvious choice.

Duke

No noticeable piston slap. The 0.08 mm clearance is what Wössner advices.

Voith

What did Andial specified with their 104.5mm 8v turbo pistons?

Penguinracer

Cheburator - did you have a Pace Products dry sump fitted to your racing 928 by Gantspeed.

I have a LR dry sump kit for my 952 using a Pace oil tank & was seriously considering Gantspeed to rebuild my engine using the Wossner pistons & rods I have, Garrett GTX3071R,Vi-Pec stand alone & various bits & pieces sourcged from Speed Force Racing (intake, head, headers, exhaust, fuel system etc) & others.
How did you find Gantspeed? Who would you recommend given that I've got virtually all the parts I need?
Tim

Cheburator

Hi Tim,

I have a dry sump, which uses the Pace pump, pulleys, bracket and I copied the pan. Those were the days, when Pace was a bit less corporate and a bit more grass-roots motorsport friendly

Gantspeed build the red 928 GTS which used to regularly race well in the Intermarque. All I can say their attention to detail was great. The fact that the engine survived with just oil/filter/plugs changes for 4 seasons is also a testament. They managed to install Motec and ITBs in a 928, which is not easy either. Overall, if you are happy with the cost they are quoting you, I don't think you would go wrong. Also worth talking to GT One in Chertsey. Not the cheapest again, but very thorough, and proper Porsche-files, regardless of where the engine is sitting...

John Mitchel and Hartech are the other two. I am deliberately not mentioning EMC as I was told, they have three 944 race engines to build as well as 2 996/Boxster lumps to build ahead of the season's start, so they would be rather swamped.

Chris White

Here is my 2 cents on the issue:
Typically bores tend to wear in a tapered fashion – so if you have out of spec piston to wall clearance there is a very good chance that the bore is tapered too. The bores wear more at the top than the bottom. If you can feel a ridge at the top of the ring travel (about ¼” down the cylinder) then you will have taper. As far as I am concerned there is no tolerance for taper. If you can measure any taper at all it’s a no go for a performance engine.
Performance motors should have piston to wall clearance towards the larger spec. The pistons will expand from heat and performance engines put out more heat!
The stock clearance spec is for stock pistons only. Do not use that spec for aftermarket pistons – use the info from the piston manufacturer. The stock pistons are extremely tight compared to any aftermarket spec.
Audible piston slap stars at about .006” wall clearance (cold motor)
And yes, a good engine builder want to pistons in hand before machining the bores. A good machinist does not trust other people’s measurements!
Lastly – if you want to do any bore reconditioning I would recommend nikasil over alusil (at least over her in the ‘states’). The nikasil coating is not a lot more cost than a proper alusil over bore and with nikasil you can have the bores finished back to stock spec or any other size. The nikasil has a much harder surface hardness and you can skip the Alusil coating on the pistons (saves $200 +/-)

Penguinracer

I spoke to Alex at EMC. He admitted that they were quite old-school & felt the liners made the motor much stronger. He opined that getting a dry sump to work well on a 951/952 with its high oil pressure was tricky & that they'd never experienced a run bearing in their race cars. He was focussing on lower-boost/more conservative builds than what is commonly discussed here.
He was of the opinion that a fair amount of the US tuning was high-boost & very aggressive & that perhaps it worked ok with US fuel but it didn't translate so well to conditions in the UK. He was talking about 320 bhp not the kind of numbers some are shooting for on these boards - interesting.
Tim

Penguinracer

Chris, are the Wossner pistons compatible with a Nikasil liner?

Chris White

Yes, pretty much anything can be used in Nikasil.

blade7

I believe EMC charge close to $2k to supply and install iron liners, I don't know if they use the main housings to line everything up ?

Cheburator

Emc will charge £1000 to instal liners (about $1650). They do only dry liners, so yes, the original cylinders are still left and just over bored to accept the cast iron sleeves. May not be the cheapest, but their cars - 944s and 968s are always at the front, and are reliable...