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RalphWiggam Samba Member
Joined: February 02, 2018 Posts: 906 Location: SouthEast
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Posted: Sun Mar 04, 2018 6:00 am Post subject: Sealing rings at top/bottom of cylinders |
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So now I've got my heads off and have found the cause of my low compression on #1 and #3. #1 was at 75psi hot whether or not oIL was added to cylinder. #3 was at 100psi. The other 2 were right on the money at 135psi. 1972 stock 1.7l by the way.
Turns out the "sealing rings" at the top of 1 and 3 were burned through in a small section. More so on #1. No other damage to the heads. I will have them rebuilt anyway while I have them out. There are also very thin rings at the base of the cylinders where they mate to the case. Should I remove these? The ones at the base of the cylinders measure .005" and look to be in good condition. The rings that burnt through at the top of the cylinders measure .03". Will compression be too high if I remove all of the rings? Should I leave the ones at the base alone and just seal the cylinders back up to the case with some permatex before reassembly? |
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Wasted youth Samba Member
Joined: July 06, 2012 Posts: 5134 Location: California's Hot and Smoggy Central Valley
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Posted: Sun Mar 04, 2018 6:14 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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The rings at the top of the pistons where they mate to the cylinders are often referred to as 'gaskets' and there is much discussion about the 'deletion' of these on the Type 4 engine and then flycutting the cylinder heads to make up for the difference of the material thickness.
I feel compression ratio should be adjusted by adding or subtracting spacers where the cylinders meet the case... and not at the combustion chamber. This prevents any chance of compression erosion/blow through/burning like what you are experiencing.
Removing or adding any rings in either location will definitely change your compression ratio. Adding rings anywhere will lower that ratio.
What I would do, as a minimum....
Remove all case studs, re-lap cylinders to case and relap cylinders to heads. Clean thoroughly and then carefully check deck height and piston stroke. Then you will need to 'CC the heads' which means determining the area of the combustion chamber using a liquid and measuring that volume of liquid in cubic centimeters (hence the term CC). Lots of Samba discussion on this process... it's really quite important to get this right, because with these measurements are found your correct compression ratio, which goes a long way in determining engine lifespan. |
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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50337
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Posted: Sun Mar 04, 2018 8:20 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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VW sent out a service bulletin recommending that the head sealing rings be eliminated and you are seeing why. What you are going to want to do is mock up the engine without the head sealing rings and determine your deck height. You do not want it to exceed 0.060" and it can be as low as 0.030" and maybe just a bit lower, this requires the making of a simple jig to hold the cylinders against the block. You may well find that without the head sealing ring you will end up right in the middle of this range. You can make adjustments by installing various thicknesses of cylinder base gaskets. Assuming you are running dished pistons and your heads haven't been cut down much then your compression ratio should be fine. If you have flat top or domed pistons or if your heads have been cut excessively then shimming the cylinders out to get a deck height of .060" may be required. Going greater than .060" will be counter productive for controlling knock. |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21512 Location: Oklahoma City
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Posted: Sun Mar 04, 2018 9:36 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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On 1.7L heads with domed or dished pistons.....as built factory deck height measured at the edge of the piston....not on the dish or dome......factors in the head gasket (which is right at .028" thick compressed and sometimes as thin as .025") and the single .010" cylinder base gasket shim..... is typically between .075" to .079".
Removing the .028" head gasket typically brings the deck to .048"- .051".
With no other changes....this typically increases compression by about 0.2:1 or 0.25:1. The 1.7L bus with twin carbs can handle this with no problems. Removing the base gasket shim makes compression increase about 0.3:1.
A .005" to .010" flycut can take compression upwards to 0.4:1 or very slightly higher. If you need to flycut.....I would leave the base shim in. This is if the combustion chambers are still stock volume. Ray |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Sun Mar 04, 2018 10:05 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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http://kentcomputer.com/77VW/techbull.pdf
. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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RalphWiggam Samba Member
Joined: February 02, 2018 Posts: 906 Location: SouthEast
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Posted: Sun Mar 04, 2018 11:26 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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raygreenwood wrote: |
On 1.7L heads with domed or dished pistons.....as built factory deck height measured at the edge of the piston....not on the dish or dome......factors in the head gasket (which is right at .028" thick compressed and sometimes as thin as .025") and the single .010" cylinder base gasket shim..... is typically between .075" to .079".
Removing the .028" head gasket typically brings the deck to .048"- .051".
With no other changes....this typically increases compression by about 0.2:1 or 0.25:1. The 1.7L bus with twin carbs can handle this with no problems. Removing the base gasket shim makes compression increase about 0.3:1.
A .005" to .010" flycut can take compression upwards to 0.4:1 or very slightly higher. If you need to flycut.....I would leave the base shim in. This is if the combustion chambers are still stock volume. Ray |
I will check the deck height. This is excellent info. Just what I was looking for. The base shims appear to have been leaking decently. How does one lap the cylinders to the case with the shim? Lap the sandwich together? Doesn't look like there was any sealant at the base of the cylinders. |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Sun Mar 04, 2018 12:08 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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RalphWiggam wrote: |
raygreenwood wrote: |
On 1.7L heads with domed or dished pistons.....as built factory deck height measured at the edge of the piston....not on the dish or dome......factors in the head gasket (which is right at .028" thick compressed and sometimes as thin as .025") and the single .010" cylinder base gasket shim..... is typically between .075" to .079".
Removing the .028" head gasket typically brings the deck to .048"- .051".
With no other changes....this typically increases compression by about 0.2:1 or 0.25:1. The 1.7L bus with twin carbs can handle this with no problems. Removing the base gasket shim makes compression increase about 0.3:1.
A .005" to .010" flycut can take compression upwards to 0.4:1 or very slightly higher. If you need to flycut.....I would leave the base shim in. This is if the combustion chambers are still stock volume. Ray |
I will check the deck height. This is excellent info. Just what I was looking for. The base shims appear to have been leaking decently. How does one lap the cylinders to the case with the shim? Lap the sandwich together? Doesn't look like there was any sealant at the base of the cylinders. |
The case comes apart and the studs taken out. A quality VW machine shop mills the case to make sure all 4 spigot lands are parallel and clean. VW used a RTV sealant at the base. The part number is in that PDF I posted but the MSDS on the part number is just a basic high quality RTV. I use the red stuff. Some folks use a little copper coat on the top of the jugs to help seal to the heads after first lapping them in. The copper coats carbonizes quickly and helps seal the head area. Carbon builds up there and that also helps. My suggestion it to toque the heads in 3 stages per the diagrams in the manual, then let it sit over night and retorque again in the morning. That should keep them tight for at least 50,000 miles. If you ever have the tin off after that, retorque them again. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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Wasted youth Samba Member
Joined: July 06, 2012 Posts: 5134 Location: California's Hot and Smoggy Central Valley
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Posted: Sun Mar 04, 2018 12:38 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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I used a two stage valve lapping compound when I lapped the cylinders to the case and to the heads. I rotated and processed them in the same fashion you would if you were lapping valves. Sandwiched the base shim in there during the Fine stage; it's held captive by the cylinder. Cleaned everything in hot soapy water when I was done. Reinstalled all the case studs, then measured out everything to set my Compression Ratio using suggestions and experience from asiab3, sgkent, wildthings and raygreenwood, and other helpful people.
I used Permatex aircraft sealant. It's dark brown, pretty runny and you don't need nearly as much as you think. No leaks. No sealant of any kind applied to combustion chamber.
My method is not as refined as a respected machine shop, but I am satisfied with the results. |
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RalphWiggam Samba Member
Joined: February 02, 2018 Posts: 906 Location: SouthEast
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Posted: Sun Mar 04, 2018 2:26 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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I don't plan on splitting the case right now. The crank play feel's just about perfect. Will confirm with gauge. I'll get some permatex aviation. Also doing the flywheel crank seal (got the gowesty one) and the oil cooler seals. The dipstick boot, Viton pushrod tube seals as well. Any other "while you're in there" items anyone knows about (without splitting the case)? Also got a new clutch disc because the old one had some oil contamination. The throw out bearing looks very clean. |
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Wasted youth Samba Member
Joined: July 06, 2012 Posts: 5134 Location: California's Hot and Smoggy Central Valley
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Posted: Sun Mar 04, 2018 3:28 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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Keep in mind there is no need to split the case to lap the jugs.
Also, buying the gasket kit is a real good way to go. It's got everything but the flywheel seal.
"while you're in there"... that really depends on how deep you went. For example, if you have the heads off, then you have the exhaust system disturbed. Time to refresh that. It would be a great time to verify all the tinwork is present and not full of hole or rust. |
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RalphWiggam Samba Member
Joined: February 02, 2018 Posts: 906 Location: SouthEast
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Posted: Sun Mar 04, 2018 4:30 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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Wasted youth wrote: |
Keep in mind there is no need to split the case to lap the jugs.
Also, buying the gasket kit is a real good way to go. It's got everything but the flywheel seal.
"while you're in there"... that really depends on how deep you went. For example, if you have the heads off, then you have the exhaust system disturbed. Time to refresh that. It would be a great time to verify all the tinwork is present and not full of hole or rust. |
All tin work is going to the powder coater tomorrow. Exhaust pieces and the piece above the muffler will get ceramic coated. I don't see how I can lap the cylinder bases without getting dirt and lapping compound into the case. I was planning on degreasing the longblock after I had everything reassembled to keep dirt and grime from getting inside. I can lap the cylinders to the heads pretty easily.
I also can't get the front fan housing piece off. Am I not seeing a secret bolt somewhere? |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21512 Location: Oklahoma City
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Posted: Sun Mar 04, 2018 5:50 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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RalphWiggam wrote: |
Wasted youth wrote: |
Keep in mind there is no need to split the case to lap the jugs.
Also, buying the gasket kit is a real good way to go. It's got everything but the flywheel seal.
"while you're in there"... that really depends on how deep you went. For example, if you have the heads off, then you have the exhaust system disturbed. Time to refresh that. It would be a great time to verify all the tinwork is present and not full of hole or rust. |
All tin work is going to the powder coater tomorrow. Exhaust pieces and the piece above the muffler will get ceramic coated. I don't see how I can lap the cylinder bases without getting dirt and lapping compound into the case. I was planning on degreasing the longblock after I had everything reassembled to keep dirt and grime from getting inside. I can lap the cylinders to the heads pretty easily.
I also can't get the front fan housing piece off. Am I not seeing a secret bolt somewhere? |
If you are not going to split the case......you just need to be very careful if you are lapping the jugs to the case. Apply the lapping compound VERY sparingly with a q-tip. In this say you can just carefully wipe around the edge....several times.
Lapping the jugs to the case is an eccellent way to get rid of corrosion and the small lip effect that can get worn into the case if things have been loose.....if you do not plan to split the case and have the registers machined flat.....as SGKent suggested....which is highly recommended.
You really do not need to lap with the shim in between.....except if it has a sharp feeling burr around the edge. In that condition this cleans that up to.
Any highly oil resistant RTV ....a VERY thin smear.....on the bottom of the jug and on the face of the case.....will work perfectly. In the permatex line.....the Ultra black is their most oil resistant. The Ultra copper and Ultra gray are not far behind. The gray and the black have the same temperature rating. The copper a little higher. All of them can more than handle the heat.
The ultra gray is the hardest and most dense. It will add about .001" give or take to the stack up as it squeezes out a little less. Ray |
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Wasted youth Samba Member
Joined: July 06, 2012 Posts: 5134 Location: California's Hot and Smoggy Central Valley
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Posted: Sun Mar 04, 2018 7:17 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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RalphWiggam wrote: |
...I also can't get the front fan housing piece off. Am I not seeing a secret bolt somewhere? |
Probably. Once all the fasteners are removed, it comes off pretty easily. Keep looking... and browse the Samba Photo Gallery for fan shrouds. You might by chance see the bolt you are missing. |
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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50337
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Posted: Mon Mar 05, 2018 12:49 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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In most instances there isn't going to be any advantage to lapping the cylinders to the case as silicone or other goop is going to be able to make a good seal here. If the jugs don't sit flat against the case, machining would be required to reface the surface, lapping would not correct this. |
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RalphWiggam Samba Member
Joined: February 02, 2018 Posts: 906 Location: SouthEast
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Posted: Mon Mar 05, 2018 7:20 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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Wildthings wrote: |
In most instances there isn't going to be any advantage to lapping the cylinders to the case as silicone or other goop is going to be able to make a good seal here. If the jugs don't sit flat against the case, machining would be required to reface the surface, lapping would not correct this. |
Noted. Going to pick up the dial indicator today to check the crank play. If it is too high, I will scrap most of my plans mentioned above and go full rebuild. Probably would make sense to do a 1911 right?
Are we allowed to talk about recommended rebuilders here? I live in Atlanta and the only person around here I trust would be Raby. Unfortunately he is pretty far outside my price range. I found Chico Performance Racing in some searching. How are they? I dont mind crating the engine up and shipping it somewhere if I need to. I am up for any suggestions.
Thanks for all the help so far. |
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RalphWiggam Samba Member
Joined: February 02, 2018 Posts: 906 Location: SouthEast
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Posted: Mon Mar 05, 2018 7:26 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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Here are some pics for kicks
Cam looks good. The lifters also look good.
Super dirty.
Last trip before I pulled the engine. At Stone Mountain, GA. |
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RalphWiggam Samba Member
Joined: February 02, 2018 Posts: 906 Location: SouthEast
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Posted: Mon Mar 05, 2018 8:09 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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So my end play is measuring at .01". That is about double the recommended end play. Is this something that I can adjust out with shims? I will pull the flywheel off later this week and see if I can measure any axial play on the thrust bearing. I am feeling somewhat of a double click when measuring end play. That second click might be the bearing. Any other advice? |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21512 Location: Oklahoma City
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Posted: Mon Mar 05, 2018 9:55 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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RalphWiggam wrote: |
So my end play is measuring at .01". That is about double the recommended end play. Is this something that I can adjust out with shims? I will pull the flywheel off later this week and see if I can measure any axial play on the thrust bearing. I am feeling somewhat of a double click when measuring end play. That second click might be the bearing. Any other advice? |
Its actually rare that the rear thrust bearing has issues unless you have incredible miles on it and its been poorly cared for. Type 4s do not have that common type 1 problem.
The few times I have seen this on type 4...actual worn thrust bearing face..... its because someone put a thrust shim in it that had burrs or rust on it.
Pull the flywheel....pull the seal.....pull the shims. More than likely you will find one or more thrust washers worn out.
The smallest spec....is at .0027".....call that .003". The largest is .005".
Being .005" out of spec is not out of the ordinary. Between 3 shims you are out .005" minimum and .007" maximum.
If the rest of the engine has moderate miles....check your shims. That may be all you need for now. Ray
Last edited by raygreenwood on Mon Mar 05, 2018 9:57 pm; edited 1 time in total |
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Busstom Samba Member
Joined: November 23, 2014 Posts: 3840 Location: San Jose, CA
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Posted: Mon Mar 05, 2018 9:56 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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Looking at your new thread about rebuilders, it sounds like you're on the right track.
Have you figured out where all of that .010 end play is coming from? If some of that is a worn thrust surface in the case, I'm afraid you're kind of hosed...a rebuild is inevitable. |
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Alan Brase Samba Member
Joined: March 28, 2004 Posts: 4532 Location: Cedar Falls, Iowa
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Posted: Mon Mar 05, 2018 10:41 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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My experience is that type 4 thrust bearings don't wallow out the case bores like in a type 1 magnesium engine. I've seen type 1 engines functioning with about .125 end play. the only limiting factor was it would affect the timing because the drive gear was hunting around so much.
Sure, change your seal if it is 20 years old or known leaking and then try to get it down to .005. But I would not lose 5 seconds sleep if it was .015, let alone ten.
Type 4 engines are super strong on the bottom. Just mind the CHT. Make sure mixture and timing do not conspire to roast the heads.
Al _________________ Al Brase
Projects: 67 sunroof bug, 67 Porsche 912 Targa, 70 Westy
Dec 1955 Single Cab pickup WANT 15" BUS RIMS dated 8/55, thru 12/55
To New owners: 1969 doublecab, 1971 Dormobile
Vanagons:
80 P27 Westy JUL 1979, 3rd oldest known US
83 1.6TD Vanagon, 87 Wolfie Westy daily driver, swap meet home |
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