TheSamba.com :: View topic - Education needed re 2.0 type 4 engine pistons

Tue Jul 12, 2011 11:20 am

THANK YOU EVERYONE, especially to VAVWFAN ,SG KENT and BLEYSENG
One can always rely on you USA folks for good advice and speedy replies.

UPDATE: Today we fitted the pistons and rings, put everything back in place and engine started on the button and ran like new :-)
very happy this end.
mvh.
Mrs Asa Gradin

------------------------------------------------
Hi all, can someone educate us please..
1979 Bay window 2.0 Fi type 4 engine.
Pistons:
1) is 4mm the standard size of oil ring?

2) Is 94mm the standard size of Piston?

or is there another size of oil ring ?
and another size of piston?
for this engine.

mvh.
mrs Asa Gradin

Tue Jul 12, 2011 11:50 am

Here is a great table of reference for you: http://www.tunacan.net/t4/reference/displace.shtml

Stock displacements are shown in orange. Each engine is actually slightly less than what people refer to it as. As you can see a 94mm piston was stock for the type 4 2 liter engine, however you can build many variations depending on the stroke.

Lots of good info here: http://www.tunacan.net/t4/
I advise you read around on there when you've got some free time.

As for the oil ring, I can't answer that for you.

Tue Jul 12, 2011 12:32 pm

Have you tried just contacting a local automotive machine shop have having them get you a generic set of rings. They can measure your pistons and then search through their books and hopefully find you something that will fit.

Tue Jul 12, 2011 10:30 pm

Wildthings wrote: Have you tried just contacting a local automotive machine shop have having them get you a generic set of rings. They can measure your pistons and then search through their books and hopefully find you something that will fit.

x2. There is no such thing as a perfect fit replacement set of rings. You buy a replacement set for that engine size and then fit them. Sometimes it is easy, sometimes it is a pain. Before you do buy a set have someone who races or a machine shop look the old pistons over. There are lots of places they wear including the ring lands and skirts.

Tue Jul 12, 2011 11:39 pm

Seems like she had been trying to source a replacement for a broken ring. Don't remember if she has said it was new pistons and a ring broke at assembly or if it was an old piston with a broken ring.

Wed Jul 13, 2011 1:10 am

Get a Bentley?--do they do Bentley manuals in SWEDISH! but of course that was never taken into consideration now was it :-)

Desertbusman wrote: Seems like she had been trying to source a replacement for a broken ring. Don't remember if she has said it was new pistons and a ring broke at assembly or if it was an old piston with a broken ring.

Wed Jul 13, 2011 3:30 am

Mrs Asa Gradin wrote: THANK YOU EVERYONE, One can always rely on you USA folks for good advice and speedy replies.
Except for 1 as you can see below- whom it seems prefers to scold rather than educate. and is no doubt as dry as the place he comes from :-)

If you're refering to the mention of the Bentley manual in my signature line that wasn't intended for you anyway. Did you take that into consideration? :lol: The Bentley manual is the Official Service Manual of Volkswagen of America. Maybe you should get VW of Sweden's official service manual. :wink:

Mrs Asa Gradin wrote: Get a Bentley?--do they do Bentley manuals in SWEDISH! but of course that was never taken into consideration now was it :-)

Desertbusman wrote: Seems like she had been trying to source a replacement for a broken ring. Don't remember if she has said it was new pistons and a ring broke at assembly or if it was an old piston with a broken ring.

Wed Jul 13, 2011 7:40 am

Hi Ms Gradin; I haven't done anything with Type 4's, but I found an interesting site for my 69 Bus that may have useful info, or may be able to point you in another direction for direct help.

In general though, if someone is going to the bother of replacing rings, it's just as easy to buy new cylinders (sometimes called barrels and/or jugs), and may have all pistons/rings properly sized within them.

"Yes" it's more expensive but a lot easier to deal with.

I have not done this myself, so I'm giving you second-hand info.

The considerations for pistons/rings and just about all moving parts of an engine is heat expansion when running. That is why "fits and clearences" are so important! Metal grows and shrinks with heat. Different materials such as rings grows at different rates than those around them, so it's important to get the measurements correct.

That said, "it's not rocket science either!!"

Remember rings have to fit in grooves of the piston, and the ring essentially is spring-loaded to fill up the space between the cylinder wall and the piston and rides on a layer of oil reducing wear. This allows the ring to seal the gap between piston & cylinder wall for compression/power strokes!

There are several rings on a piston and the gaps on them MUST be staggared to allow pressure to be built up in the cylinder.....

All other advice herein is valid; a local person with knowledge; a machine shop or parts store may be able to help. But equally inmportant is determining "what" made the ring break in the first place, and any damage that may have occured as a result!

The piston groove may be damaged and the gap on the flat side of the ring is excessive and/or inordinate, causing the ring "land" (where the flat part of the ring sits in the groove), to have excessive play. It could even be localized, though doubtful. In that event the piston could be machined to correct the land, but really,,,,,it's not worth it! It's easier and cheaper to buy new, unless you own a machine shop - lol.

Equally true is that the cylinder may be out-of-round causing interference and ring breakage. Again, new cylinders & pistons already set-up would be excellent alternatives.

I wish I had more experience in your problem, but many herein have done it a lot. Understanding the basics can sometime help you visualize the problem beforehand and make wise decisions......

Here's that website that may have some info you can glean:
http://www.aircooled.net/gnrlsite/resource/articles/t1hpeng.htm

Good luck!!

Wed Jul 13, 2011 8:15 am

Hello sir, super education, I thank you kindly. Ive learned more from your letter than I have learned in months.
most appreciated and advice we shall follow starting tomorrow morning.
mvh.
mrs Asa Gradin

VAVWFAN wrote: Hi Ms Gradin; I haven't done anything with Type 4's, but I found an interesting site for my 69 Bus that may have useful info, or may be able to point you in another direction for direct help.

In general though, if someone is going to the bother of replacing rings, it's just as easy to buy new cylinders (sometimes called barrels and/or jugs), and may have all pistons/rings properly sized within them.

"Yes" it's more expensive but a lot easier to deal with.

I have not done this myself, so I'm giving you second-hand info.

The considerations for pistons/rings and just about all moving parts of an engine is heat expansion when running. That is why "fits and clearences" are so important! Metal grows and shrinks with heat. Different materials such as rings grows at different rates than those around them, so it's important to get the measurements correct.

That said, "it's not rocket science either!!"

Remember rings have to fit in grooves of the piston, and the ring essentially is spring-loaded to fill up the space between the cylinder wall and the piston and rides on a layer of oil reducing wear. This allows the ring to seal the gap between piston & cylinder wall for compression/power strokes!

There are several rings on a piston and the gaps on them MUST be staggared to allow pressure to be built up in the cylinder.....

All other advice herein is valid; a local person with knowledge; a machine shop or parts store may be able to help. But equally inmportant is determining "what" made the ring break in the first place, and any damage that may have occured as a result!

The piston groove may be damaged and the gap on the flat side of the ring is excessive and/or inordinate, causing the ring "land" (where the flat part of the ring sits in the groove), to have excessive play. It could even be localized, though doubtful. In that event the piston could be machined to correct the land, but really,,,,,it's not worth it! It's easier and cheaper to buy new, unless you own a machine shop - lol.

Equally true is that the cylinder may be out-of-round causing interference and ring breakage. Again, new cylinders & pistons already set-up would be excellent alternatives.

I wish I had more experience in your problem, but many herein have done it a lot. Understanding the basics can sometime help you visualize the problem beforehand and make wise decisions......

Here's that website that may have some info you can glean:
http://www.aircooled.net/gnrlsite/resource/articles/t1hpeng.htm

Good luck!!

Wed Jul 13, 2011 8:47 am

I assume you have the engine out already, and partially pulled apart???

I found in Samba that there are Mahle barrels/pistons available; I've never used them, nor know anything about their product. I don't know if there is any machining to be done or if the rigs, gaps, lands etc are already done?!? I just don't know the details!!

I'm an aircraft mechanic by trade and have only done this type of work on radial aircraft engines 30+ years ago, and it was pretty much direct replacement. I've since moved onto other lines of work, and nobody uses piston engines in the airline industry anymore; so it's a dying art!

For them, the piston/rings were already set-up. It only required pusing the piston down far enough to expose the wrist pin bore, and sliding the pin onto the connecting rod; pushing the cylinder down onto the case and torqueing it up.

Hopefully, that's the way they come to you, which makes life a whole lot easier.

Once again; "good luck!"

Wed Jul 13, 2011 8:53 am

I was under the impression that theses are/were new pistons and clylinders.

Wed Jul 13, 2011 9:08 am

OK, but if you buy new barrels/pistons, lets say "Mahle's;" are the rings already lapped for the grooves; end gaps set and staggared??

I'm getting ready to pull apart a bad motor myself and may need to know this before I buy something. I don't mind doing the work myself, it's just that I'd rather not because "I have no time!!"

God, retirement looks better and better all the time! - lol

Wed Jul 13, 2011 9:35 am

No, they are not set up and you should always check what you buy to make sure its in spec and set up correctly. Just too many variables.

Wed Jul 13, 2011 11:04 am

Evidently there is also quite a difference between T-1 and T-4 engines. I can't imagine anyone doing a socalled rebuild on a T-1 engine and not just putting on a set of new barrels and pistons. Cheap and very easily obtainable and they always will be with the zillions of Bugs and other models around the world. And there is no difficulty in getting rings for them also if you break one. About everyone sells the Meyle's which are available in numerous sizes and types. Cast and forged.
But a lot of Samba people use the old barrels and pistons and just put in new rings on type 4's. I'd supose because of high cost and lack of availability.
With t-1's the Meyles come with the rings installed on the pistons. I always remove them to be able to completely clean the pistons and rings. Sure don't want any manufacturing or handling contaminates involved. They have to be removed anyway to measure the gaps. I remove and install them by hand versus using a piston ring tool. Never had one break but obviously it can happen. Maybe that's what happened to the OP.

Wed Jul 13, 2011 11:17 am

On the type 4, you'll want the rings removed anyways to get your deck height measured. Much easier to do without the rings.
These are weight matched by Jake's crew.
http://www.aircooledtechnology.com/store/product.php?productid=16893&cat=275&page=1

Wed Jul 13, 2011 11:53 am

there is no difference in how a T1 or a T4 set of pistons is ringed other than sizes and specs. The process is still the same. The ring end gaps have to be measured in the barrel and and the side gap of the rings in the lands have to be measured. All must be within clearance. The rings, pistons and barrels must then be washed in hot as you can stand soapy water and dried well. I usually spray with WD-40 and oil lightly before reassembly to stop rust. The ring will have directions which is 1.2 and oil. and it will show which side is up. Moly rings will require a special finish on the barrels almost like glass.

Replacement rings are sometimes tighter in the lands because they assume that the pistons they are going in are worn a little. Usually the rings are at the wider side of the specs so they can be too tight on a new piston where the lands are at the smaller side of the specs.

Most common cause of ring breakage on a new piston is installation error. They are almost all cast iron and they snap all too easy. Best solution is to put on some gloves and play with the old rings to get the feel of how easy they are to break.. i say wear gloves as old rings can be very sharp at the edges, especially when they snap.

Usually one has to buy a set of rings for 4 pistons.