Engine M44/07 150hp, M44/05 163hp??
If you can find them! I've been looking for OE flat top pistons for a while, and only the dished ones are available new. I looked for months for decent used ones, but didn't find any. If you've found a good set, go for it!
I wound up getting new Wössner pistons, and I'm crossing my fingers that the Swain Tech coating will hold up...
I wound up getting new Wössner pistons, and I'm crossing my fingers that the Swain Tech coating will hold up...
-
PSU_Crash
- Posts: 243
- Joined: Sun Apr 06, 2025 4:34 pm
- Location: Decatur, Tennessee
- Has thanked: 166 times
- Been thanked: 94 times
I have used swain tech for their white lightning manifold and turbo coating in the past. 15 years later, it's still holding strong.Oringojin wrote: Tue Apr 14, 2026 2:42 am If you can find them! I've been looking for OE flat top pistons for a while, and only the dished ones are available new. I looked for months for decent used ones, but didn't find any. If you've found a good set, go for it!
I wound up getting new Wössner pistons, and I'm crossing my fingers that the Swain Tech coating will hold up...
'86 Zermatt Silver 944 N/A 
'86 Mitsubishi Starion - Purpose built SM class Autocross car
'87 Chrysler Conquest - Mid LS Swap
'86 Mitsubishi Starion - Purpose built SM class Autocross car
'87 Chrysler Conquest - Mid LS Swap
And did you get more power?Oringojin wrote: Tue Apr 14, 2026 2:42 am If you can find them! I've been looking for OE flat top pistons for a while, and only the dished ones are available new. I looked for months for decent used ones, but didn't find any. If you've found a good set, go for it!
I wound up getting new Wössner pistons, and I'm crossing my fingers that the Swain Tech coating will hold up...
Thank you. 
And did you get more power?
[/quote]
Yes, a lot more, but the pistons were one part of a list of upgrades, and I was comparing the newly built motor to my tired old 300 000 kilometer original.
I did have the satisfaction of blowing past a BMW XM getting on the highway, though!
[/quote]
Yes, a lot more, but the pistons were one part of a list of upgrades, and I was comparing the newly built motor to my tired old 300 000 kilometer original.
I did have the satisfaction of blowing past a BMW XM getting on the highway, though!
I'm not sure I understand your question. The block itself is "alusil", it's an alloy with silicon cristals embedded in the aluminium. It works because the hard silicon is what is rubbing against the steel piston rings. The pistons have a coating on the skirts to protect them from the cyliner walls and prevent the aluminium from friction welding itself to the aluminium in the cylinder walls and ripping out chunks of aluminium and silicon. That's bore scoring.944year83 wrote: Thu Apr 16, 2026 12:43 pm Has anyone changed the piston rings on a 944 without the Alusil and everything worked fine?
The OE pistons from Mahle and Kolbenschmidt had a proprietary iron or tin coating that worked very well. The aftermarket pistons had problems with their coatings holding up, but supposedly the latest batch with their MoS2 coatings are supposed to be better.
In my exchanges with Tom Barker, he explained that his frustration with the aftermarket piston coatings breaking down led him to start sleeving the blocks systematically, so if that's what you mean by "without the Alusil", that's what he recommends.
When I told him I was starting over with a new block, I could almost see him rolling his eyes as he was typing his e-mail, basically warning me that wouldn't have been his first choice...
-
Tom
- Site Admin
- Posts: 8543
- Joined: Fri Jun 25, 2021 2:04 pm
- Location: Silicon Valley, CA
- Has thanked: 888 times
- Been thanked: 3820 times
- Contact:
Nikasil is also a good option, without the challenges of sleeves...Oringojin wrote: Thu Apr 16, 2026 11:31 pmI'm not sure I understand your question. The block itself is "alusil", it's an alloy with silicon cristals embedded in the aluminium. It works because the hard silicon is what is rubbing against the steel piston rings. The pistons have a coating on the skirts to protect them from the cyliner walls and prevent the aluminium from friction welding itself to the aluminium in the cylinder walls and ripping out chunks of aluminium and silicon. That's bore scoring.944year83 wrote: Thu Apr 16, 2026 12:43 pm Has anyone changed the piston rings on a 944 without the Alusil and everything worked fine?
The OE pistons from Mahle and Kolbenschmidt had a proprietary iron or tin coating that worked very well. The aftermarket pistons had problems with their coatings holding up, but supposedly the latest batch with their MoS2 coatings are supposed to be better.
In my exchanges with Tom Barker, he explained that his frustration with the aftermarket piston coatings breaking down led him to start sleeving the blocks systematically, so if that's what you mean by "without the Alusil", that's what he recommends.
When I told him I was starting over with a new block, I could almost see him rolling his eyes as he was typing his e-mail, basically warning me that wouldn't have been his first choice...