CU Engine Cylinder Seals??

[Andyroo]

I'm fully stripping my 2.0 CU engine down and today I've removed the cylinder head for cylinders 1 and 2.

The Haynes manual states-
Note the sealing ring at the top of each cylinder and remove it.

There were no seals.

Then after removing the cylinders/barrels it says 'Recover the second sealing ring at the base of the cylinder'
Again, there wasn't any.

The engine was working fine before it was removed.
Should there be seals or is the Haynes manual wrong?

There is a seal shown in the exploded diagram for the head.

Andy

[937carrera]

They should be there

The fire ring at at the top could still be stuck to the head, the bottom to the barrel ?

https://volkswagen.7zap.com/en/rdw/typ+ ... /101-5000/

[davidoft1]

The top rings were discontinued by VW, the bottom ring is like a gasket really , if the engines been rebuilt it will have neither

[937carrera]

Really, I thought the top one in particular was critical to setting deck height as well as sealing. If neither are then then the deck height (piston to cylinder head) cannot be set correctly. That's why there are three thicknesses of "3"

Kind of important to me as I have a CU to rebuild, as well as potentially two 412 engines at some point

[davidoft1]

Really, I thought the top one in particular was critical to setting deck height as well as sealing. If neither are then then the deck height (piston to cylinder head) cannot be set correctly. That's why there are three thicknesses of "3"

Kind of important to me as I have a CU to rebuild, as well as potentially two 412 engines at some point

You can alter deck height with shims under the cylinder, I’ll find the bullitin from Vw, it was quite early on, the suggestion being the gas rings burned and caused failure( which I would agree with having seen it) and that no shim is a more robust seal and gives better heat transfer

[itchyfeet]

You can write what I know about Aircooled on a postage stamp but I have heard of people lapping the barrel to the head with fine grinding paste, perhaps this is why.

[ajsimmo]

VW heads use sealing rings, but new AMC heads delete the rings and the barrels need to be lapped in to the head. Do you have AMC heads, by any chance? As mentioned, the lower barrel rings are both seals and shims to adjust deck height. If none were fitted it's had a bad rebuild. Measure deck height on reassembly, and fit the appropriate thickness shim.

Sent from my ONEPLUS A3003 using Tapatalk

[Andyroo]

They are VW heads.
Well, I’ve only stripped the 1+2 side so far.
Some of the above comments are a bit worrying.
I’ve looked on the usual web sites and can’t find any seals or shims for CU cylinders.
Not sure what to do now when I come to rebuild.

[itchyfeet]

Sarran will be along soon to give you some advice.

[sarran1955]

Hello,

The crank case to barrel shims like this:



are available here:

https://www.serial-kombi.com/en-GB/tran ... 82-n321399" onclick="window.open(this.href);return false;

These are used to set the deck height, ie the distance between the piston crown and the top of the cylinder. Typically 1.8mm

The rings in the combustion chambers are de-compressor rings to allow the engine to run on 95RON.

like this:



from here:
https://www.serial-kombi.com/en-GB/tran ... 82-n312387" onclick="window.open(this.href);return false;

If you want to raise the compression to run 98RON petrol and have original heads, then lap in the barrels to the head .

Make sure that the valve guide play is acceptable, and I systematically use new stainless steel exhaust valves.

Hope that covers it...

Air-Cooled Bliss...

Cordialement,

[Andyroo]

Fantastic.
Thanks Sarran
I’ll get some ordered.

Are there different thicknesses I need to consider?
And also, it’s got me thinking, if my engine doesn’t have them how was it working ok?

[sarran1955]

Are there different thicknesses I need to consider?

No

And also, it’s got me thinking, if my engine doesn’t have them how was it working ok?

I'll bet there are signs of blowby..

Cordialement,

[Andyroo]

Ok.
Thanks again Sarran, and everyone else who’s answered.

[davidoft1]

If your engine doesn’t have them
Now they were removed as they aren’t needed, you need to check your heads to see if they have been machined, it’s also very easy to miss them as the get welded in place and carbon’d up, I’ve only see blow by on cylinders WITH the shims

[Andyroo]

Thanks davidoft,

I’ll take a closer look tomorrow night in case they are there and look to be part of the head/case.
If I’m not sure I’ll upload some pictures.


Are the seals/shims re-usable or should they be replaced everytime?