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Liner O-ring sealant

9881 Views 9 Replies 7 Participants Last post by  Akram, 
J
Does anyone use any kind of sealant on the liner O-rings. I am about to put the new liners into my block, and the section where the liners meet (flat edges) are pretty crorroded, and I am concerned whether the liner O-rings will seal properly. I plan to wet the orings with Hylomar, but should I use something else like permatex aviation form a gasket, or Ultra Grey RTV? I have never done this before, and any advice would be most helpfull.


John R
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John M
Some people do...I don't. Not Hylomar...but epoxy from what I have been told. But I would however sand all the corrosion off the seal mating surface. 600 grit smooth. I am sure more opinions to follow.

Best Regards,
John M
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ghnl
When I rebuilt the engine in our '84 Spdier a couple of years ago I cleaned the sealing surfaces thoroughly, used new liner O-rings (wow are they tiny/thin...!) and also painted on a thin smear of RTV. Operative word is thin smear. Big goobers of RTV are not good!

So far so good...
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J
My concern with RTV is, I would think you need to seat the liners, install the pistons, and torque the head all before the RTV fully hardens. You want the RTV to be able to flow out and seal all the divots, nooks and crannies before it hardens up, right? Did you smear the RTV at the base of the liners, and then insert them, or smear a thin film around the seat in the block before inserting the liners. I guess I am trying to make it more complicated than it needs to be. I have sanded the seating and sealing surfaces where the liners contact the block with 600 grit, but the narrow region between liners is pretty badly pitted. I need to do more sanding and cleaning. The old liners didn't leak, but they were stuck in really bad and took about 4 hours to get them free. I finally made a tool and pounded them out from the bottom. See picture below.

John R

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John M
On your picture there....

I would continue sanding quite a bit. Start with like a 200 or so wet and work that O ring seating surfaces (both the flat and vertical edges) until you have shiny metal. Then smooth it out with 320, 400, and then 600 all wet.

On your RTV question/concern....I would imagine just utilizing some hold downs on the liners would resolve your concern.

Best Regards,
John M
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1
I have sanded the seating and sealing surfaces where the liners contact the block with 600 grit, but the narrow region between liners is pretty badly pitted. I need to do more sanding and cleaning. The old liners didn't leak, but they were stuck in really bad and took about 4 hours to get them free. I finally made a tool and pounded them out from the bottom. See picture below.
Click to expand...

John, I think you'll be OK if you make another pass at sanding and cleaning the sealing surfaces. Even though they are thin, once you have them in place and torqued down, the mechanical seal of the liner seals is quite good. I've always been a little ambivilent about putting additional sealants on the sealing surface. Apparently it can be done, however.

One thing you really should do is add a can ot "Alumaseal" to your coolant. It's good "mouse milk" :) in that the finely ground aluminum flakes will seal hairline leaks like those that might occur at the liner/block seal. This stuff really works well.
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A
My local motor engineers take a witness from the seating of the liners in the block for me, and an equivalent amount off the bottom of the liner to ensure that the big-end bolts don't hit. I then use the standard rubber band dry and so far no problems. I also ensure I have the four thou protrusion of the liner above the deck height and take a further witness to ensure the mating surface block to head is parallel to the crank axis. Giulietta Normale liners are longer than Veloce ones so there is meat to go at. Before doing any of this ensure that your liners are sufficiently long.
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MrT
I put my first V6 engine together last spring, and it's still doing well. I cleaned the mating surfaces of the sleeves and block with steel wool, but cleaned it thoroughly afterward to avoid any chance of abrasive in the engine. The car is doing just fine with my assembly of the O-rings. I was inclined to use Hylomar myself, just as an assurance measure for sealing, and I have used that material on water pumps and other gasket surfaces for years with no unhappiness whatsoever. It always cleaned up nicely on the few occasions I had to take such a joint apart.

But you know everyone has a favorite material he was told to use when learning. If it works, he'll tell those he teaches to use it. They will quite likely do so.

Michael
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J
Well I now have the liners/pistons in and the head on. I wound up just cleaning the liner seat better (sanding with 600 grit) and using Hylomar on the o-rings. I plan on using Alumaseal in the coolant as insurance. I'll let you all know how it turns out once I get it running again. Thanks for all the advice.

John
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A
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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