AA barrel to case face

Discussion in 'Mech Tech' started by Gnasha, Nov 20, 2019.

  1. I was mating the barrel faces to a decked case. I notice the landing face is very small.
    Is this normal?

    AA barrel
    7D91A63C-CDC1-4A67-B8C3-F12C812E3115.jpeg

    VW
    DE48DA31-A268-49BD-B566-57CFEE3B6367.jpeg

    Thanks for looking.
     
  2. Wouldn’t image it would make much difference as long as it seals. No pressure behind it. The heads will hold the barrels down.
     
  3. 77 Westy

    77 Westy Supporter

    That’ll leak – probably. The stud ‘hole’ should not cut into the seal face and it should be like the VW barrel. The pic is a AA Biral cylinder but you can see the difference.
    IMG_4836 (Medium).JPG
     
    Last edited: Nov 21, 2019
    Gnasha likes this.
  4. The case face has a slighty taper which I think is as wide as the mating face on the barrell, although I havent measured it.

    I think ill ask AA for their comments.
     
  5. 77 Westy

    77 Westy Supporter

    The case face should be flat and the bore parallel but there is a chamfer – is that what you mean by a taper? The case bore is 100mm dia. the barrel OD at the sealing face is 99.8mm and the chamfer is about 1.5mm. Although there is no pressure in the crankcase there is plenty of oil spray coming off the crankshaft and con rods into the gap between the barrel and the case and I doubt if that AA barrel will seal. Are all the barrels the same?

    Here’s a pic of an iron cylinder I have, this one is a Mahle, the stud hole doesn’t touch the barrel sealing face.
    IMG_6980 (Medium).JPG
     
    Last edited: Nov 25, 2019
  6. 77 Westy

    77 Westy Supporter

    What did AA say?
     
  7. Response from AA

    "We seal the case side of the liner with black silicone I and we don’t have any problems with it."

    I'm not convinced, I'm going to take some measurements of the worst case scenario and see excactly how much face-to-face contact there is.
     
  8. Ive measured the faces of the barrels and the chamfer on the case faces. This tells me the width of the contact face.

    I reckon its approx 1mm, what do you think?
     

    Attached Files:

  9. 77 Westy

    77 Westy Supporter

    The sealing face should be the flat area on the case and corresponding area on the barrel around the whole circumference, it’s usually around 5mm wide but only 1mm or so on that AA barrel. The AA answer fills the void between the OD of the barrel and ID of the case – a bodge in my opinion.

    You have three examples of how the barrels should be and I wouldn’t accept that AA barrel or their ‘fix’, although it would probably work.

    Never use silicone sealant anywhere in an engine – bits of it fall off and get trapped in the strainer if you’re lucky or in the oil passages if you’re not.

    Incidentally, didn’t you say on another thread that you had 96mm AA pistons? If you have a set of 94mm VW barrels why don’t you have them bored out to 96mm?
     
    Last edited: Nov 23, 2019

  10. Ive sent the above pics to AA and await there response.

    I would never use silicone anywhere in any engine.

    All of the photos in the last message are AA barrels. The smallest face overlap using a rule is about 0.04" 1 mm, it doesnt inspire me with any confidence.

    I have two sets of 94mm barrels. One set is being used to build another engine. The remaining set has some damaged fins from a PO all VW OEM. However, its a great idea which I'll condsider if I dont use the AA barrells.
     
  11. 77 Westy

    77 Westy Supporter

    It’s not difficult to repair damaged fins and I’d use VW barrels bored to 96mm rather than those AA ones. AA quality can be a bit dubious and those barrels are an example of poor QA, they should have been rejected from the manufacturer and not offered for sale IMO.
     
  12. Plenty of metal left on an opened up stock barrel.. though I have just spent best part of a day finishing off the "opening out" as it was a little shy of 96mm and pistons were tight... fin repairs ok too.. hopefully with JB weld![​IMG]

    Sent from my SM-G930F using Tapatalk
     
    Last edited: Jul 3, 2020

  13. Im their defence apart from this important defect the QA was spot on. I'll wait for there responce from the last mail containing the measured photos. I'm already looking for a decent set of barrels just in case, so I think my mind has been made up.

    The cost of time, money and effort to building it and then find it leaks........... I would be devastated.

    I'm a little annoyed its come to this, but thats life.
     
  14. I'd like some of these 039 101 301 C
     
  15. 77 Westy

    77 Westy Supporter

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