Dougs951S

I spoke with Duffin Engine service in San Antonio today, they are familiar with building 944 engines but my conversation with them today was brief do to my schedule and it raised some questions they were not able to answer.

For one, although they have done many 944 engine, they claimed to have never dry sleeved a 944 engine, or any alusil engine for that matter. They also said they would not install darton sleeves on any motor, period and would not elaborate why.

Secondly, they raised doubts that there would be enough meat on the 944 block's wall to successfully dry sleeve, which we all know is not the case.

They also stated the factory alusil pistons would not be compatible with an iron liner, can anyone shed some light on that? If that is the case, I would probably go with new wossners.

In any case, they quoted me 320 dollars labor for the installation, which I thought was an excellent price. Any recommendations on some good sleeves that wont break the bank? I don't know if there is really a great difference between them, I was looking at some melling sleeves like these:

https://www.summitracing.com/parts/mel-csl116/overview/

Also just a question, but what is keeping a sleeve that does not have a flange from moving besides the interference fit between it and the cylinders? Is it recommended that I have the block counterbored and get flanged sleeves, or have people successfully used straight flangeless sleeves in a 951 motor?

Would anyone like to address any of the comments Duffin made to me? I don't know that much about the details of sleeving the block but I have made up my mind that this (probably) is the route I am going.

Thanks guys!

edit: Is it possible to safely go to 104mm on dry sleeves?

V2Rocket

If you recall I had a sleeved 2.5 block a while back that was un-flanged...There is so much surface area and the interference fit so tight that I wouldn't worry about it, as long as the sleeves don't pop out or sink when the block is heat cycled.

That is a killer price to sleeve the block...I might even want to send one there for that price...lol

I know 944online sleeves 944 blocks with the intent of using stock pistons. I think the issue is finding a piston ring in the right dimensions that is sleeve compatible, rather than the piston coating.

But if you are getting sleeves done...go nuts, you can get your 944 rods bushed to fit a SBC piston pin, if you wanted, and you could pick a larger bore.
They need to shave the block deck after sleeving...944 deck is nominally 9.055" and SBC is nominally 9.025", so have them cut a little extra off the top for optimal quench....

odonnell

And piston coatings are relatively cheap. You would be out the door for under $150 with Swaintech or equivalent

Dougs951S

well, I'd love to use stock pistons because I have a set that are essentially new, absolutely flawless and look like they were never inside an engine. I also got rods with it, not looking into stroking at this time but would be interested potentially in SBC pistons. Basically I see my options thus:

#1: Sleeve block + new 104mm wossners/SBC pistons. Cost = ~1350 with the wossners, maybe less with SBC pistons

#2: Bore and hone block + new 101mm wossners. Cost = 1400+

#3: maybe one of the 4 blocks I have on hand would be a candidate for a simple hone job + use my stock pistons. Cost = whatever the cost of having a shop rehone my cylinders, and thats a big if since; out of my four spare blocks; one needs a crack welded near the deck, two need a .040" overbore to clean up, and the other probably need at least a .020" bore too.


Any idea where I'd find rings to use with stock pistons inside a steel bore and what that might cost? I found a post from you a long time ago linking to a set of Totalseal rings but they were pretty expensive @ 380 dollars or so and you seemed unsure if they were the right set?

As for the Chebby pistons, IIRC 104mm bore is as large as you can safely go on a dry sleeve. I know guys go bigger with MID's. at ~104mm, it would probably be more economical for me to get chevy pistons vs the wossners and it might let me bump the compression up a bit too. Found a good set that would work in 4.020" bore that would give me 9:1 CR and .056" deck clearance at nominal 9.025" deck height + .040" HG.

V2Rocket

You should be able to buy a set of good SBC pistons for what you could sell those clean 951 pistons for.

Since you are really good with tuning I wouldn't question you using hyper-eutectic pistons instead of forged pieces if you went with SBC parts. All the OEM's use hyper pistons in their production boosted stuff, only in really high-end motors do they put forged bits in (GT40, McLaren, etc).

In that case just run whatever rings come with the pistons.

You could probably even buy a set of 8 pistons, get 2 blocks sleeved to fit those pistons, and then sell the finished spare block + spare 4 pistons to cover your costs. The quote you got to sleeve that block is about half or less than half of what most other places would charge.

Dougs951S

I have a bunch of options in SBC pistons. I am interested in gaining non interference, but not at the expense of having less than optimum quench. I would assume this is something then that would need to be addressed via flycutting, and not by just simply having a lot of deck clearance? Assuming my HG is .040" thick compressed, the ideal piston in terms of having good quench would have a compression height around 1.560" which is common for 400 pistons. Assuming 9.025" deck height, that gives me .046" quench including the HG.

V2Rocket

If you get the block cut after sleeving you could get a 0.30 or so cometic gasket to tighten it up...

Look up "Lindy Tools", they make "in-head piston valve notch cutters", I bought one for my 16v swap, nice piece and fast shipping.

DannoXYZ

Lots of vendors make sleeves. I recommend flanged chromoly sleeves.

Also Laust rents out a fly-cuttting tool. You use it with the pistons in the engine as the cutters are aligned perfectly with the axis of the valve.

Dougs951S

Not sure his tool would work for my intake valves as they are 49mm (+4mm oversize).

harveyf

I have a block from a turbo that was scratched in one bore. I got all 4 bores resleeved locally with straight (no flange) steel sleeves by a reputable shop. I have never finished assembling the motor. That said, I have sent myself a few emails regarding rings. One says: Talked to Mike Lindsey. He recommends Goetze piston ring set 100 mm as used in 911 Turbo '93 thru '94.

Van

If you have steel/iron liners, I'd go with Total Seal rings.

And, if you went through all the trouble to sleeve an engine, it's worth the expense to get new (custom) pistons (like from JE or someone), that has a tighter tolerance on the piston ring grooves than old 944 pistons have... and you should order the pistons *first* so the engine shop can hone the sleeves to the right size.

Long story short: if you're going through he time and expense to do this, do it right.