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> Bought a 2+L Mystery Engine, what's would you do next .
Dave_Darling
post Apr 15 2018, 09:32 PM
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Either trust that the previous builder knew how to calculate compression, or take it apart and measure all of the pertinent volumes so that you can calculate compression. Then you can decide if flat-top pistons would help or not.

I personally think you should just run it...

--DD
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Dougster
post Apr 19 2018, 10:44 PM
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QUOTE(Spoke @ Apr 15 2018, 10:10 AM) *

I bought a 2L "mystery" engine with dual Weber carbs as well. ...

When I took it apart, I found out the pistons were already 96mm and have the dished pistons like the OP.



Wow! someone else with dished 96's !! They do exist ! I thought I was in the twilight zone. I have not been able to locate any mention of them, much less a picture (so thanks for posting). Do you remember if yours have a the divit in the center? Doesn't matter I guess, just wondering. Yea, I guess I'll bolt mine back together and try to enjoy.

Question though - cylinder honing: should I bother? I don't remember seeing crosshatching (kind of didn't pay close attention/in a hurry), I think there was some carbon build up on one of the cylinder walls. Can it be DIY'ed with the harbor freight hone that fits on a drill? if so... replace rings or re-use?

Also, this engine certainly has some oil leaks. I'll be getting the viton seals for the tubes but I noticed the "head gasket" rings that fit between the cylinders and heads were kind of crappy, you could see an un-even seal on them (narrow area of carbon) on one side/edge. And they didn't seem absolutely round and their fits into the recess on the head were not perfect. Is that normal ? Is there a preferred replacement for these? Likewise, is there a similar seal used on the cylinder/block end? 'cause it's probably oilier at that junction..
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bbrock
post Apr 20 2018, 07:44 AM
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QUOTE(Dougster @ Apr 19 2018, 10:44 PM) *

Question though - cylinder honing: should I bother? I don't remember seeing crosshatching (kind of didn't pay close attention/in a hurry), I think there was some carbon build up on one of the cylinder walls. Can it be DIY'ed with the harbor freight hone that fits on a drill? if so... replace rings or re-use?


I can't say whether you need to hone, but I had a bit of rust in a cylinder on my engine that was stored in humid sheds for too many years. I honed it out with the HF hone on a drill. Worked great.

(IMG:http://www.914world.com/bbs2/uploads/post-20845-1490843407.jpg)

(IMG:http://www.914world.com/bbs2/uploads/post-20845-1490843583.jpg)
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Dougster
post Apr 20 2018, 11:10 AM
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QUOTE(bbrock @ Apr 20 2018, 08:44 AM) *

I honed it out with the HF hone on a drill. Worked great.


Thanks Brent, I think i'll just plan on that then.. mine may have been some rust too, but didn't seem major. As for rings replacement..I'm not sure that I could even find the correct rings if I want to replace them since these particular pistons are soo rare.

Anyone have info/recommendations for the 'head gasket rings'? and/or seals at the cylinders/case junction ?
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Dougster
post Apr 21 2018, 12:22 AM
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Ok, from what I'm starting to understand, what I'm calling "head gasket rings" is technically referred to as "sealing rings".. and apparently the latest wisdom is to not use them unless necessary. I read that VW recommended removing them at some point. Also, it sounds like there is a "shim" at the other end (cylinder to case), that is used to adjust the compression ration. Do I have this right ?

I am going to measure the CC of the head using plexiglass/syringe/oil. Then, I assume I can get the CC of the dished piston with the same method, right ? I do plan to do that w/piston installed btw. Then how does one get the current deck height number/? using simple digital calipers while spacer tubes are bolted down over the long head studs?
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porschetub
post Apr 21 2018, 12:54 AM
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QUOTE(Dougster @ Apr 21 2018, 06:22 PM) *

Ok, from what I'm starting to understand, what I'm calling "head gasket rings" is technically referred to as "sealing rings".. and apparently the latest wisdom is to not use them unless necessary. I read that VW recommended removing them at some point. Also, it sounds like there is a "shim" at the other end (cylinder to case), that is used to adjust the compression ration. Do I have this right ?

I am going to measure the CC of the head using plexiglass/syringe/oil. Then, I assume I can get the CC of the dished piston with the same method, right ? I do plan to do that w/piston installed btw. Then how does one get the current deck height number/? using simple digital calipers while spacer tubes are bolted down over the long head studs?


Good call on the honing,remember if you can feel any grooves with your fingernail the barrels are toast.
Grant or Hastings rings are pretty good,pretty sure they do 96mm check the websites.
Best to get your heads cleaned and checked over also,they may need work.
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bbrock
post Apr 21 2018, 11:28 AM
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I don't know that there is consensus on the head gasket. I don't remember details from reading those old threads except that at least one knowledgeable person said the VW recommendation to remove them was for a specific application (only bus maybe?) and didn't apply to us. The only other part I remember was that after all the reading, I decided I will be installing them when my heads go back on, but would love to hear opinions as it is a decision that I'll be making soon as well.

Tom Wilson's book has a good description for measuring deck height. It's worth having if you don't already.
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Dougster
post Apr 21 2018, 11:44 AM
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Yea I found this VW bulletin..
http://www.ratwell.com/mirror/www.dolphins...m/techbull.html
it specifies certain G engines but not the GA (which is what I have), so maybe that IS just bus engines. Would be nice to understand why the recommendation for eliminating them on some engines and not others. Anyway, I'm ordering Tom Wilson's book now, thanks.
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MarkV
post Apr 21 2018, 11:47 AM
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QUOTE(bbrock @ Apr 21 2018, 10:28 AM) *

I don't know that there is consensus on the head gasket. I don't remember details from reading those old threads except that at least one knowledgeable person said the VW recommendation to remove them was for a specific application (only bus maybe?) and didn't apply to us. The only other part I remember was that after all the reading, I decided I will be installing them when my heads go back on, but would love to hear opinions as it is a decision that I'll be making soon as well.

Tom Wilson's book has a good description for measuring deck height. It's worth having if you don't already.


There is lots of information about the pros and cons but I think the consensus is not to use the sealing rings. They are prone to blowout failure, I didn't use them on my rebuild. I lapped the cylinders to the heads with valve lapping compound.
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bbrock
post Apr 22 2018, 08:23 AM
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QUOTE(MarkV @ Apr 21 2018, 11:47 AM) *

QUOTE(bbrock @ Apr 21 2018, 10:28 AM) *

I don't know that there is consensus on the head gasket. I don't remember details from reading those old threads except that at least one knowledgeable person said the VW recommendation to remove them was for a specific application (only bus maybe?) and didn't apply to us. The only other part I remember was that after all the reading, I decided I will be installing them when my heads go back on, but would love to hear opinions as it is a decision that I'll be making soon as well.

Tom Wilson's book has a good description for measuring deck height. It's worth having if you don't already.


There is lots of information about the pros and cons but I think the consensus is not to use the sealing rings. They are prone to blowout failure, I didn't use them on my rebuild. I lapped the cylinders to the heads with valve lapping compound.


Do you have to compensate for removing the head sealing ring with shim rings at the base of the cylinder?
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MarkV
post Apr 22 2018, 09:20 AM
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QUOTE(bbrock @ Apr 22 2018, 07:23 AM) *

QUOTE(MarkV @ Apr 21 2018, 11:47 AM) *

QUOTE(bbrock @ Apr 21 2018, 10:28 AM) *

I don't know that there is consensus on the head gasket. I don't remember details from reading those old threads except that at least one knowledgeable person said the VW recommendation to remove them was for a specific application (only bus maybe?) and didn't apply to us. The only other part I remember was that after all the reading, I decided I will be installing them when my heads go back on, but would love to hear opinions as it is a decision that I'll be making soon as well.

Tom Wilson's book has a good description for measuring deck height. It's worth having if you don't already.


There is lots of information about the pros and cons but I think the consensus is not to use the sealing rings. They are prone to blowout failure, I didn't use them on my rebuild. I lapped the cylinders to the heads with valve lapping compound.


Do you have to compensate for removing the head sealing ring with shim rings at the base of the cylinder?


The sealing rings aren't all that thick and I had to add shims to set my C/R anyway. Both Jake & Mark Henry condemn the use of the sealing rings..... that was enough for me.
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Dougster
post Apr 22 2018, 11:04 AM
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QUOTE(bbrock @ Apr 22 2018, 09:23 AM) *


Do you have to compensate for removing the head sealing ring with shim rings at the base of the cylinder?


I'd assume if we could locate shims for the case side, that equals what was already there + the thickness of the seal rings - then replacing the shims would be ideal for maintaining the compression ration. However, like was mentioned those seal rings are really thin, so I'm not sure if it's possible.

I plan to lap the head/cylinders, it's common procedure when deleting the seal rings but another questions I've been wondering.. is there any such lapping done at the case side with cylinders, shims, case ? Also, have I read that there's a paper gasket that gets eliminated too?
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MarkV
post Apr 22 2018, 12:00 PM
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QUOTE(Dougster @ Apr 22 2018, 10:04 AM) *

QUOTE(bbrock @ Apr 22 2018, 09:23 AM) *


Do you have to compensate for removing the head sealing ring with shim rings at the base of the cylinder?


I'd assume if we could locate shims for the case side, that equals what was already there + the thickness of the seal rings - then replacing the shims would be ideal for maintaining the compression ration. However, like was mentioned those seal rings are really thin, so I'm not sure if it's possible.

I plan to lap the head/cylinders, it's common procedure when deleting the seal rings but another questions I've been wondering.. is there any such lapping done at the case side with cylinders, shims, case ? Also, have I read that there's a paper gasket that gets eliminated too?


The registers were really hard to get clean and flat on my engine. When I first checked the deck height it was different on every cylinder. There was paper and glue residue from the factory paper gasket on the registers. Once I got the registers clean the deck height was close to the same on all 4 cylinders. I had my cylinders bored to 96mm and used flat top KB pistons. If I remember correctly I had to ad a .030 shim to get the compression ratio right.

http://vwparts.aircooled.net/Cylinder-Base...-base-shims.htm
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