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Discussion Starter #1
Didn't see any recent threads on this sealant topic on Nord 2L engines, so figured I'd put it out there.

Question 1: My machine shop (much experience with Alfas) advises that I should use sealant (aviation, because it remains pliable) on the liner o rings. I'll likely do that, but curious if that's what most folks are doing these days. My block is pretty smooth and clean where the liners seat.

Question 2: Assuming I use a sealant, does that mean I have to get everything from the liners all the way through the head installed in the same day before the sealant dries? I'm no pro at this, so prefer to take my time. Could I just seat the liners and torque (10 lb) down the liner hold down tools instead and let the sealant dry? And then take my time with everything else?

Appreciate any guidance.
 

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question 1, yes i do that also

question 2, seal it, mount it, holded it and torque it down and take your time to do the rest
 

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Can you share the sealant your Alfa experienced machine shop is using.

Thx

Ken
 

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I smear some RTV around the base of the liners before inserting them. So it's less that I'm sealing the O rings than sealing the liner-block interface. But sure, some RTV gets pushed up onto the O ring as the liner is inserted.

I never even thought about the liner needing to move down a precise amount as the head gets torqued down - just let them bottom out and installed my homemade hold-downs (sections of electrical conduit + large washers). Since I'm using flexible RTV, the liners can still move relative to the block; I'm just increasing the spring constant by adding the stiffness of the RTV to the stiffness of the O ring. Epoxy wouldn't behave this way - with a hardening adhesive, yea, torquing down the head would be prudent.

All this aside, I'll freely admit that if the O ring sealing surfaces on your block aren't pitted and you are using new O rings, this is all probably unnecessary. But hey, it's so easy to do and I'd feel like such an idiot if I got leaks in that area, that why not?
 

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Discussion Starter #8
As an aside, I'll freely admit that if the O ring sealing surfaces on your block aren't pitted and you are using new O rings, this is all probably unnecessary. But hey, it's so easy to do and I'd feel like such an idiot if I got leaks in that area, that why not?
Yeah - that's sort of where my head is on the matter. Mating surface is actually quite good (after machine shop made it so), but seems like a "won't hurt" sort of thing as long as it doesn't make me rush the rest of the job trying to get the head on before the sealant cures.

BTW - the machinist recommended Permatex Aviation Sealant and some Subaru sealant (pricey) because they stay pliable. If anyone really wants to know the Subaru one, let me know and I'll post a picture of the tube.
 

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I used Permatex Blue, general purpose RTV. Inexpensive insurance.
 

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After you set the liners, install the hold-downs, fill the block up with Distilled water, and put newspaper under the motor ( I assume the crank is out/oil pans off). Wait a day or so and see if it leaks.
 

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Throw the o-rings away and use a sealant ... RTV for a street engine, epoxy for a race engine. You need to thoroughly clean the machined surfaces so the liners drop freely into the block. Afrer checking the fit degrease with a detergent like Formula 409. Solvents only dilute the oil, a detergent will emulsify it.

Apply a 4-5 mm bead of sealant about 10 mm below the step and insert them in the block. Make sure the flats on the liners do not touch. Touching can keep them from seating squarely and distort the bore. Use your new head gasket and install the head with 10-15 lb-ft of torque. Let it sit for 8-10 hours. Remove the head and make sure all the liners are even. If so, finish assembling your engine ... liner hold-downs no longer needed and your head gasket is still good.

This method is too slow for production, but offers improved sealing, extra support (especially with epoxy) and a chance to verify proper seating of the liners. And should the head ever need to be removed, prevents them from shifting and breaking the seal.

-jim
 

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Discussion Starter #12
This sounds like you’ve done this approach a time or two. Thanks for the insight. Much appreciated!
 

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Didn't see any recent threads on this sealant topic on Nord 2L engines, so figured I'd put it out there.

Question 1: My machine shop (much experience with Alfas) advises that I should use sealant (aviation, because it remains pliable) on the liner o rings. I'll likely do that, but curious if that's what most folks are doing these days. My block is pretty smooth and clean where the liners seat.

Question 2: Assuming I use a sealant, does that mean I have to get everything from the liners all the way through the head installed in the same day before the sealant dries? I'm no pro at this, so prefer to take my time. Could I just seat the liners and torque (10 lb) down the liner hold down tools instead and let the sealant dry? And then take my time with everything else?

Appreciate any guidance.
I’ve rebuilt dozens of Alfa engines - street and SCCA prep. I have never had any problems with O rings on the liners. Clean block lands and new or like new clean liners the OEM o rings work fine.
 

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G'day Crackie, I'm another one who has done multiple rebuilds on different 2000s for road and rally. If the 45 degree o ring sealing faces in the block are not pitted severely there is no reason to use any type of sealant. All will be fine.

When I have been concerned about the corrosion on the sealing face I have still refrained from using sealant there but have put silicone sealant around the bores in the block (not on the liner--which would mean that sealant would be pushed up when the liner goes in). With this method there is a backup water seal, and you can see a ring of sealant at the bottom of the bores, which is reassuring. Never had a problem and the liners can be easily removed next time.

Just a quick query re your machine shop making sealing surface good. If any metal is taken off the 45 degree o ring sealing surface the o ring will not be compressed to the correct specification, this could possibly allow a leak. If any metal is (also?) taken off the liner seating surface this would could restore the o ring crush, but, it would of course lower the liner in the block and so reduce head gasket compression, which would not be good.
 

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G'day Crackie, I'm another one who has done multiple rebuilds on different 2000s for road and rally. If the 45 degree o ring sealing faces in the block are not pitted severely there is no reason to use any type of sealant. All will be fine.

When I have been concerned about the corrosion on the sealing face I have still refrained from using sealant there but have put silicone sealant around the bores in the block (not on the liner--which would mean that sealant would be pushed up when the liner goes in). With this method there is a backup water seal, and you can see a ring of sealant at the bottom of the bores, which is reassuring. Never had a problem and the liners can be easily removed next time.

Just a quick query re your machine shop making sealing surface good. If any metal is taken off the 45 degree o ring sealing surface the o ring will not be compressed to the correct specification, this could possibly allow a leak. If any metal is (also?) taken off the liner seating surface this would could restore the o ring crush, but, it would of course lower the liner in the block and so reduce head gasket compression, which would not be good.
Yes indeed. Everything has to be inspected and if not to spec, measures have to be taken.
 

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After you set the liners, install the hold-downs, fill the block up with Distilled water, and put newspaper under the motor ( I assume the crank is out/oil pans off). Wait a day or so and see if it leaks.
So long as the mating surfaces are within spec and not pitted or damaged And the liners have the correct dimensions above the block (to provide the correct O ring crush) all will be good. I suppose a silicone might assist but I fear removal. Whenever parts are assembled with any cementing product, disassembly will be more difficult. You might be the next guy. Personally I am a novice Alfa engine rebuilder (3 motors) and have not had any issue with the O rings
 

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It is true that liners can sometimes be difficult to remove and I think that is due to electro-chemical action between iron, aluminum and water. I think that silicone sealant is more likely to inhibit that action than exacerbate it.
 

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Use one or the other. You don't need both. O-rings will reliably seal the joint but won't offer any support to the liners. Pressure from the head gasket is the only thing holding them in place.

There is considerable side force on the liners on the power stroke. At WOT and twenty degrees ATDC, cylinder pressure can reach more than 1000 psi. With a piston area of 8.59 square inches (84 mm), the side load on the piston/liner will be more than 3000 lbs. That's a lot to ask of the head gasket alone.

Throw the o-rings away and stop changing head gaskets.

-jim
 

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Do I have to change the liner O-rings? My liners were honed only. I got new rings for the pistons and so the liners were not removed.I need some quick advise here because the block is in the machine show and should be done in a day or two.
 
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