MykT

I am in the early stages of a 944 engine block restoration, and have been doing the initial research/homework. The bores are in good shape with the exception of some small pitting on the number one cylinder. (same cylinder that a broken piston ring was discovered but not sure if the issues are related to each other.) It appears that the popular options are sleeving or Nikasil platting. However, the factory manual describes reconditioning by boring, dressing and lapping, and makes no mention of platting. Looking for some wise input about the options.

Gage

This information has been covered and covered and covered again here and elsewhere, it is easily searchable and makes for great reading. When the "research" is done, please come back with specific information as to what you are attempting to do, on which 944, and why, along with photos and specific questions.

dlknight

The Porsche workshop manual describes the entire machining process to recondition alusil bores by enlarging them to the next repair size.

The kolbenschmidt documentation is also a good read if you want to understand the process (they are the company who created the alusil process and made the original 944 blocks).

51708_ks_50003804-02_web.pdf (ms-motorservice.com)

Jfrahm

Generally easier and cheaper to get a good short or long block. Just shipping the engine somewhere for plating would cost more, as probably would a set of oversized pistons.

V2Rocket

short answer - the manual doesn't talk about plating because Alusil is not plating. the entire upper engine block casting is made of Alusil - they just do the special machining process on the cylinder bores to make it work like that.

Nikasil was developed a few years later and used a lot in the 90s-00s. you are in WI - you can reach out to 928motorsports or these guys to get your block nikasil plated.
https://www.usnicom.com/

MykT

Thank you for the information. It' been difficult to fine a machine shop that does the Alusil reconditioning as described in the factory manual, although many claim to know how to do it. ( "We don't need that fancy Porsche/ metric stuff)I. 'm skeptical.
I am a stone's throw from Millennium so that seems the likely path.I have heard only good reviews. I have read contrary opinions about using the original pistons. The guys there say OEM pistons are OK. Anyone have any experience with the factory set in Nikasil?

michaelmount123

There are way too many horror stories about Alusil reconditioning and 944 sleeving by "reputable" shops that have resulted in failure. Since either of these processes is risky, your Nikasil direction is both a safe and effective solution.

Use 964 rings which are made for Nikasil, just make sure your pistons use the same ring dimensions. Do be aware your old pistons are likely worn out which will compromise ring seal, but could be used. A better solution is to invest in new pistons for your build as long as they are configured for the 1.5/1.75/3mm 964 rings.

four0four

I've had success with alusil refinishing through a (sort-of) nearby and very qualified shop.


...But Nikasil appears to be a better option, and since you're probably closer to Millennium than I was to my shop it would seem crazy not to take that route!

MykT

Thank you so much for great information. Just a enthusiastic novice, greatly appreciative for the input.

michaelmount123

Which 944 are you working on? 2.5L?

Chalt

1) What do you mean by sort-of?
2) How much did that set you back to have it done?
3) How many years/miles have you put on the engine since the service?

walfreyydo

Anyone have any thoughts on nikasil compatible performance pistons? Im looking at rebuilding my S2 engine and may go forced induction, and was thinking going the sleeving route to open up more aftermarket piston options (JE, etc).

Nikasil seems like a good route but not sure if there are good aftermarket performance piston/ring options. I have also heard from Hartech (porsche engine guru's facebook group) that sleeving these engines is much simpler and less prone to issues than the flat 6 engines in the boxster/911/cayman, so I am suprised to hear @michaelmount123 suggestion that these are prone to issues with sleeving, which is making me second guess the sleeving route (either wet or dry).

Im curious what thoughts people have on performance pistons and nikasil vs sleeving, and what the options are out there for nikasil-compatible aftermarket/forged pistons/rings in particular. Being in WI as well, it appears I have some good options for nikasil.

dlknight

Nikasil plating is the "best" solution, but it is also considerably more expensive than retaining the alusil and following the workshop manual processes.

I'm having my block rebored to 100.5 following the workshop manual process and it is about 1/2 as much as I was quoted to have the block Nikasil plated.

You also need to remove ALL ferrous metal from the block, that means all the plugs and studs before you can Nikasil plate.

V2Rocket

Problem with alusil these days is that there’s only 1-2 shops in the US that seemingly know how to work with it.

In 2018 or so I contacted Sunnen themselves looking for recommendations and they didn’t even know who still did the stuff.

In 2019 I bought Wossner pistons and a block that had supposedly finished to 100.5mm for an ambitious project. Turns out the block was only rough bored and I couldn’t find an alusil finishing shop within 500 miles of Nashville.

That’s what made me sell off all my 944 engine stuff and do a swap.

Tony5

@walfreyydo for what it's worth there's a shop in the western Chicago area that claims to do alusil work. Teter Automotive. They've posted a bit about it on their FB page.