Mid-sleeves

[gruhsy]

Informative video.

I think Michael Mount and Chris White are the only two successful with doing MIDS properly.

[michaelmount123]

This video is informative and points out the primary cause of MID sleeve failure is machining faults. I believe the MID sleeve design provides very beneficial upgrades to a 2.5 (open deck) block, but the machining is critical to success. Darton's web site offers MID sleeve installation for the 944. Who could be better to do the job correctly? I'd use this service for the confidence alone.

[gruhsy]

This video is informative and points out the primary cause of MID sleeve failure is machining faults. I believe the MID sleeve design provides very beneficial upgrades to a 2.5 (open deck) block, but the machining is critical to success. Darton's web site offers MID sleeve installation for the 944. Who could be better to do the job correctly? I'd use this service for the confidence alone.

I can’t confirm this but I recall someone posting somewhere outside Carpokes that they had Darton install MID’s and a sleeve or sleeves dropped from improper tolerance.

I hope that wasn’t true or a cause.

[Tom]

This video is informative and points out the primary cause of MID sleeve failure is machining faults. I believe the MID sleeve design provides very beneficial upgrades to a 2.5 (open deck) block, but the machining is critical to success. Darton's web site offers MID sleeve installation for the 944. Who could be better to do the job correctly? I'd use this service for the confidence alone.

For my stock-ish build on a reasonably ok block, I'm still planning on Nikasil (Right?). I've just heard way too many stories about sleeved blocks failing. @chris white is the exception, but everyone else I've heard about seems to have a sketchy track record...

[333pg333]

I can't see how a properly machined block allows for a sleeve to fall. Having said that, it only has to drop a very small amount for the seal to fail. But I can't see how with a stepped sleeve and the block being machined correctly to accept the sleeve, then how can it drop? Especially if they mount it slightly proud and deck the surface. But yes, we do read of failures with sleeving. I've gone down the MiD path despite having some failures many years ago which we put down to the inexperienced machinists not knowing what they were doing. Prior to the RP968 Thor motor they ran a Chris White block. Pumping 28-30psi into that engine and the sleeves didn't fail. I think it's still all together and a back up for Rod. Maybe he'll put it in his road car. The machinists I used this time around were known and recommended by Darton. When I switched to a different stud the machinists had to install these newer/larger ones. They were clamped down to 130lbs and the machinist fully expected to have to hone the sleeves again due to the higher load and them going out of round...but no, they didn't. Which goes to show how strong these sleeves are and hopefully how well they installed them.

[blade7]

For my stock-ish build on a reasonably ok block, I'm still planning on Nikasil (Right?). I've just heard way too many stories about sleeved blocks failing. @chris white is the exception, but everyone else I've heard about seems to have a sketchy track record...

Nikasil plating would be my first choice, but afaik only one place does it in the UK, and they certainly know how to charge for their services. Not sure if it's the same in the US, but every bit of ferrous metal has to be removed from the block before it's plated? Plus on 104mm blocks the windage ports are retained, not sure if any kind of sleeving does that?

[gruhsy]

I believe it is 100% machinist not knowing or caring about what they are doing.

Partially why I am hesitant with Millennium Technologies in Winnipeg for Nikasil.

I would only need to figure out honing.

Joseph’s son is fortunately finished his cancer treatments and Joe is back at work. He is doing some machining for my work right now so available again .


I can do MID sleeves at Fidelity using their 6 Axis Makino and accuracy down to almost molecular size….slight exaggeration for making a point!!

[blade7]

CNC is obviously the most accurate machining method, linked to the main bearing centerline, though we are talking about old Alusil blocks. I was surprised that while extracting a stud from a block, I managed to snap off the lug it was in. Plus I believe the liners should be installed a couple of thou proud of the deck surface, not sure if that's because they can sink a bit, when the head is pulled down, or for a better seal into the head gasket?

[Tom]

I can't see how a properly machined block allows for a sleeve to fall. Having said that, it only has to drop a very small amount for the seal to fail. But I can't see how with a stepped sleeve and the block being machined correctly to accept the sleeve, then how can it drop? Especially if they mount it slightly proud and deck the surface. But yes, we do read of failures with sleeving. I've gone down the MiD path despite having some failures many years ago which we put down to the inexperienced machinists not knowing what they were doing. Prior to the RP968 Thor motor they ran a Chris White block. Pumping 28-30psi into that engine and the sleeves didn't fail. I think it's still all together and a back up for Rod. Maybe he'll put it in his road car. The machinists I used this time around were known and recommended by Darton. When I switched to a different stud the machinists had to install these newer/larger ones. They were clamped down to 130lbs and the machinist fully expected to have to hone the sleeves again due to the higher load and them going out of round...but no, they didn't. Which goes to show how strong these sleeves are and hopefully how well they installed them.

Your first sentence is probably the key. If you go to about the 7:15 mark of that video above, they basically blame sinking and other failures on improper machining, and make passing reference to tolerances down to half a thousandths on multiple axes.

[Tom]

CNC is obviously the most accurate machining method, linked to the main bearing centerline, though we are talking about old Alusil blocks. I was surprised that while extracting a stud from a block, I managed to snap off the lug it was in. Plus I believe the liners should be installed a couple of though proud of the deck surface, not sure if that's because they can sink a bit, when the head is pulled down, or for a better seal into the head gasket?

According to that video, they can be left proud to create a 'stepped deck' for increased head gasket seal. Kind of half way to o-ringing, which they can do in addition to the stepped deck.