Mid-sleeves

[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.

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...

If your stockish rebuild were mine, Tom, I'd definitely go with Millinnium/Nikasil and use pistons configured for 964 piston rings. It's proven, durable, and avoids pitfalls.

[Tom]

It's proven, durable, and avoids pitfalls.

Those are the magic words this time around!

[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.

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.

I suppose we also have to take into account different expansion rates between alu block and ductile iron sleeves. As we've noted, it only has to shift a fraction of a human hair's thickness for the seal to fail. Amazing that we can make anything last haha!!

[gruhsy]

I will used Nikasil on my 3.0L block and my original 87 2.5L block.

There are a couple other blocks that I think will get the MID’s. I need the challenge!

[blade7]

Just my opinion, but Darton sleeves for a road engine, seem like a sledgehammer to crack a wallnut. Sure if the bores in the block are ruined, and you want to keep the original block/engine number. But Nikasil or dry sleeves seem to work well enough.

[gruhsy]

Just my opinion, but Darton sleeves for a road engine, seem like a sledgehammer to crack a wallnut. Sure if the bores in the block are ruined, and you want to keep the original block/engine number. But Nikasil or dry sleeves seem to work well enough.

One block has a cracked cylinder.

There is a new racetrack here also and a second in the works.

Have 3 cars now and probably getting a 4th.

[michaelmount123]

I agree with Blade7 that MID sleeves are primarily for performance/high boost applications, and to strengthen the 2.5 free standing cylinders. For most street engines or even track engines with limited boost, Nikasil is probably the way to go, whether with a 2.5 or 3L block. There has been so many issues with wet sleeving reported in the forums, best to avoid them.

I've never tried the Athena or SCE cut ring gaskets, but they may work well. I used alot of Cometic MLS gaskets but there's an important torque method that they I've never seen mentioned. The ARP head studs and their 100 ft. lb. torque will cure many head lift issues. In the end, a proper tune by an legitimate expert will prevent a ton of aggravation, extra expense, and time.

[michaelmount123]

Since no one asked.....

When torquing a MLS (Cometic) head gasket, once you complete 3 steps using the center to outside factory sequence, the center nuts will be loose. This is because the center sealing ridges in the gasket take time to relax into their sealed position. Once the sequence is complete in 3 steps, go back to #1, back it off and re-torque directly to the torque spec. Then follow the same final procedure for #2 through #10, one at a time.

If you're using an MLS gaskets and either of the center cylinders are leaking, you can probably just back-off and re-torque the nuts in sequence to seal the head. Mark the nuts and notice the center ones will turn an additional amount. You're welcome.

[michaelmount123]

Ok, last comment on this. I promise.

I always use the large, thick Porsche head washers rather than the washers supplied by ARP. The factory washers will spread the clamping load further and be easier on the head casting itself. If you're using the factory nuts, the taller 12mm nuts are for the cylinder head, the shorter 12mm nuts are for the lower case half (girdle).

[gruhsy]

Since no one asked.....

When torquing a MLS (Cometic) head gasket, once you complete 3 steps using the center to outside factory sequence, the center nuts will be loose. This is because the center sealing ridges in the gasket take time to relax into their sealed position. Once the sequence is complete in 3 steps, go back to #1, back it off and re-torque directly to the torque spec. Then follow the same final procedure for #2 through #10, one at a time.

If you're using an MLS gaskets and either of the center cylinders are leaking, you can probably just back-off and re-torque the nuts in sequence to seal the head. Mark the nuts and notice the center ones will turn an additional amount. You're welcome.

Some tech from Darton.

Noted the re-torque head during break in. Read from start to finish of course

Michael are the flanged Ductile sleeves in the block you did that I have Darton?


https://dartonsleeves.com/tech-publicat ... ch-center/


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