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Tcash
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Joined: July 20, 2011
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Location: San Jose, California, USA
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RalphWiggam
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Joined: February 02, 2018
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Location: SouthEast
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 Posted: Thu May 24, 2018 6:43 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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I just read the whole thread and there was really no conclusion.
Im pretty sure my elevated oil temps from switching to the 20w50 oil are possibly due to my weak pressure relief spring.
What I really couldnt find through searching was how timing affected oil temps. I thought I read somewhere on here that increasing the timing can lower the oil temp. I figure increasing timing would increase CHT, but my CHTs never go over 300, so I figured I might have some room to play with... |
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SGKent 
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Joined: October 30, 2007
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Location: Citrus Heights CA (Near Sacramento)
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| Posted: Thu May 24, 2018 6:48 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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piston seals both places, more on the top. When you mic and inspect it, the top is where the wear is. The combination limits how much oil can flow when open. It is closed at lower pressures, meaning at idle no oil other than leakage will be passing over the top. You'll notice that in the photo of the bore there are two relief channels cut well below the surface and that go all the way to the top of the bore.
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RalphWiggam
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Location: SouthEast
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| Posted: Mon May 28, 2018 8:24 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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So about 210 miles on the rebuild now.
First fill up mpg =9.94
Second fill up mpg = 11.89
Third fill up mpg = 14.13
These were all prematurely filled because my gas gauge is currently not working. Im gonna have to cut a hole in the back floor to get to the sender. First and second fill up are probably off a bit from the cam breakin and constant tuning.
Put about 50 miles on it yesterday. Oil temps were running in the 235 range at 3800rpm on the highway with mid 80s ambient. Reading from the oil pressure relief location. This is with a new 62mm relief spring. I'll borrow the laser thermometer at work and verify that temp later this week. Oil pressure is more than 10psi/1000 until my oil temps get above 220. I think I'll try to find a new relief piston and try that.
Also changed my trans fluid to the recommended gl-4 from Napa and my shifting is feeling better the more I drive it. |
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raygreenwood
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Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
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| Posted: Mon May 28, 2018 8:36 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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| RalphWiggam wrote: |
So about 210 miles on the rebuild now.
First fill up mpg =9.94
Second fill up mpg = 11.89
Third fill up mpg = 14.13
These were all prematurely filled because my gas gauge is currently not working. Im gonna have to cut a hole in the back floor to get to the sender. First and second fill up are probably off a bit from the cam breakin and constant tuning.
Put about 50 miles on it yesterday. Oil temps were running in the 235 range at 3800rpm on the highway with mid 80s ambient. Reading from the oil pressure relief location. This is with a new 62mm relief spring. I'll borrow the laser thermometer at work and verify that temp later this week. Oil pressure is more than 10psi/1000 until my oil temps get above 220. I think I'll try to find a new relief piston and try that.
Also changed my trans fluid to the recommended gl-4 from Napa and my shifting is feeling better the more I drive it. |
Yes....as I noted pages ago....and your mileage increase is indicating (if its accurate).....your engine is getting broken in slowly.
As rings wear in.....and Deves rings are notable for slow break in.....the compression and efficency will rise. As the comression and efficiency rise.....head temps will drop a little and oil temps can follow a bit.
Switching to a thicker oil is a good experiment. But at the moment it does not appear to be the total answer. Just keep in mind (and I realize you are) that 20/50 is thick enough that it can cause some cooler bypass at highway speeds.
Ray |
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SGKent
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Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Mon May 28, 2018 12:33 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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| that 20/50 is thick enough that it can cause some cooler bypass at highway speeds. |
Ray that might be true in your AC car but not in a bus. The cooler doesn't bypass when the oil is really hot and the pressure falls. Bypass with 20w50 in a bus iat highway speeds is an old wives' tale. The slot(s) dump(s) oil to the sump (or back to the pump on late cases.) That only happens when the pressure is high. High pressure doesn't happen in a bus when the oil is 220F+ even with 20w50. VW alludes in their manuals to situations where this can occur however any bus owner who drives at highway speeds and climbs grades knows that overly thick oil is the farthest thing on a bus owners mind at those moments. A small VW AC car is a different situation.
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raygreenwood
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Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
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| Posted: Mon May 28, 2018 1:20 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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| SGKent wrote: |
| Quote: |
| that 20/50 is thick enough that it can cause some cooler bypass at highway speeds. |
Ray that might be true in your AC car but not in a bus. The cooler doesn't bypass when the oil is really hot and the pressure falls. Bypass with 20w50 in a bus iat highway speeds is an old wives' tale. The slot(s) dump(s) oil to the sump (or back to the pump on late cases.) That only happens when the pressure is high. High pressure doesn't happen in a bus when the oil is 220F+ even with 20w50. VW alludes in their manuals to situations where this can occur however any bus owner who drives at highway speeds and climbs grades knows that overly thick oil is the farthest thing on a bus owners mind at those moments. A small VW AC car is a different situation. |
Sorry...again...wives tale my ass. 
And 20/50...is thicker than 10/30....at any temp. Yes....tbey both thin out when hot.....but even at 225 F....the 20/50 is thicker.
If all is new and all is perfect....yes there should be no problem on the late case with the slot.....but in systems that are 40+ years old with ancient springs of sispect tension....which is what we are working on right now....right?.....then this is a common issue.
The relief valve does NOT havd to bypass completely. Its not a on/off light switch. If its being compressed down even some when it should not be....you can be losing part of the oil pressure you shouldn't be.
You seem to keep running on some strange belief that I have not owned or driven a bus or worked on any. You are incorrect. And no.....they are not that different. You just think they are because you havent had experience with the other type 4 cars enough....in my opinion...to see all of the differences and similarities.
My lowest area of experience type 4 wise....is in fact in the last two years of hydro cases with the slot. And.....this is not one of those. Its an early (for a bus) 1.7L .
I also think Ralph is partly on the right track. The oil control valve is actually just as important as the oil relief valve. It is the primary pressure builder in the system. It IS the proverbial thumb over the end of the hose.
If the pressure control valve is not operating right...leaking piston or weak spring....your system oil pressure will be erratic....and the oil pressure relief valve will be erratic.
Either way....if your oil pump is tight.....and the crank bearings are tight...especially the rods....you should not need 20/50 to keep stable oil pressures at 230 F oil temp.
This is why I keep asking...what the oil pump gear lash and endplay was....and what the fijal checked tolerances of main and rod bearings were....and we should add to that...what the rod side tolerances are.
Even if they are in the middle of the book tolerances....the max tolerances on rod side clearance, oil pump gear lash and rod bearings....are so large at their extreme....that if evsrything is in the middle or upper middle.....each of those can be a 5%+ oil pressure loss at warmed up/hot conditions.
So think of a 15% across the board pressure loss.....and what Ralph is experiencing now. Add to this any discrepancy in oil control or relief springs......and this is the wide variation you can get....even with 20/50 oil.
The 20/50 oil....is a bandaid. On an older engine or one just slapped together as a refurb....I think its totally fine.
On a brand new $6-7000 rebuild with lots of better than stock parts.....I would want to know why before getting too far down the road.
I am starting to understand with the pressure control valve....that years ago Jake Raby and others....were onto something when they replaced the piston and spring with a carecully tuned length of rod to make a fixed orifice.
And as you note...VW got rid of it altogether as part of a package of modes for hydraulic lifters. I found years ago just how critical it is to the actual oil cooler relief valve functioning reliably. Its a pain in the back side.Ray |
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SGKent
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Location: Citrus Heights CA (Near Sacramento)
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| Posted: Mon May 28, 2018 4:07 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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Ray you have posted here before that you do not own a bus. I encourage you to buy one and restore it. Drive it awhile and see the difference between it and a bug etc. The one place you will get bitten in a bus is highway speeds on a hot day then pulling a grade or pushing a headwind. Your oil WILL get very hot, typically 250 F to 260 F. You can compare viscosities on this chart from the RAtwell page. The viscosity of 20w50 @ 212F is approximately the same as SAE 30 @ at 160F. Richard goes into a lengthy discussion about buses and oils on that page. The thermal question asked in this thread is valid for a bus. No one in a bug. 411 or 914 comes even close to the heat a bus generates unless they are racing around a track near wide open for hours.
Richard's numbers came directly from Valvoline. FWIW the oil that isn't used gets dumped back to the sump (or recirculated in a late case). When the oil is hot the pressure is so low that no oil is bypassing the cooler. If cold oil bypasses the cooler why would that bother anyone? Cool oil is the goal. The 20w50 is used because it holds the 10 PSI /1000 when it is 250F - 260F that a bus can see (and higher if pushed harder). In the case of this thread - he is seeing low pressures 40 degrees lower than that. Like you I suspect that the pump is worn. I also don't recall if plasti-gauge was used on all the bearings. I am not suggesting every bus needs 20w50 oil but when it is 108F here and we are driving 50 mph the oil is very thin. Add a long grade and it gets even thinner.
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RalphWiggam
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Joined: February 02, 2018
Posts: 906
Location: SouthEast
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| Posted: Mon May 28, 2018 5:21 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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Plastigage was used on the rods and they were all within spec. Side play on the rods was very good. I didn't plastigage the center crank bearing. That's the only one you can gauge right?
I didn't check lash or endplay on the oil pump. This was not in Wilson's book that I can remember.
Maybe I'll go ahead and order one of those EMW oil control valve solid replacements just to rule it out. They are pretty cheap.
Kent, let me verify my oil temp's with a laser thermometer on the sump before we assume that I am losing pressure at my indicated > 210. It might actually be 230 when I start to lose pressure. I am also not too far off (if at all) of the published spec of 42psi at 2500rpm at 158deg. |
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RalphWiggam
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Joined: February 02, 2018
Posts: 906
Location: SouthEast
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| Posted: Tue May 29, 2018 7:48 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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| raygreenwood wrote: |
| SGKent wrote: |
| Quote: |
| that 20/50 is thick enough that it can cause some cooler bypass at highway speeds. |
Ray that might be true in your AC car but not in a bus. The cooler doesn't bypass when the oil is really hot and the pressure falls. Bypass with 20w50 in a bus iat highway speeds is an old wives' tale. The slot(s) dump(s) oil to the sump (or back to the pump on late cases.) That only happens when the pressure is high. High pressure doesn't happen in a bus when the oil is 220F+ even with 20w50. VW alludes in their manuals to situations where this can occur however any bus owner who drives at highway speeds and climbs grades knows that overly thick oil is the farthest thing on a bus owners mind at those moments. A small VW AC car is a different situation. |
Sorry...again...wives tale my ass.
And 20/50...is thicker than 10/30....at any temp. Yes....tbey both thin out when hot.....but even at 225 F....the 20/50 is thicker.
If all is new and all is perfect....yes there should be no problem on the late case with the slot.....but in systems that are 40+ years old with ancient springs of sispect tension....which is what we are working on right now....right?.....then this is a common issue.
The relief valve does NOT havd to bypass completely. Its not a on/off light switch. If its being compressed down even some when it should not be....you can be losing part of the oil pressure you shouldn't be.
You seem to keep running on some strange belief that I have not owned or driven a bus or worked on any. You are incorrect. And no.....they are not that different. You just think they are because you havent had experience with the other type 4 cars enough....in my opinion...to see all of the differences and similarities.
My lowest area of experience type 4 wise....is in fact in the last two years of hydro cases with the slot. And.....this is not one of those. Its an early (for a bus) 1.7L .
I also think Ralph is partly on the right track. The oil control valve is actually just as important as the oil relief valve. It is the primary pressure builder in the system. It IS the proverbial thumb over the end of the hose.
If the pressure control valve is not operating right...leaking piston or weak spring....your system oil pressure will be erratic....and the oil pressure relief valve will be erratic.
Either way....if your oil pump is tight.....and the crank bearings are tight...especially the rods....you should not need 20/50 to keep stable oil pressures at 230 F oil temp.
This is why I keep asking...what the oil pump gear lash and endplay was....and what the fijal checked tolerances of main and rod bearings were....and we should add to that...what the rod side tolerances are.
Even if they are in the middle of the book tolerances....the max tolerances on rod side clearance, oil pump gear lash and rod bearings....are so large at their extreme....that if evsrything is in the middle or upper middle.....each of those can be a 5%+ oil pressure loss at warmed up/hot conditions.
So think of a 15% across the board pressure loss.....and what Ralph is experiencing now. Add to this any discrepancy in oil control or relief springs......and this is the wide variation you can get....even with 20/50 oil.
The 20/50 oil....is a bandaid. On an older engine or one just slapped together as a refurb....I think its totally fine.
On a brand new $6-7000 rebuild with lots of better than stock parts.....I would want to know why before getting too far down the road.
I am starting to understand with the pressure control valve....that years ago Jake Raby and others....were onto something when they replaced the piston and spring with a carecully tuned length of rod to make a fixed orifice.
And as you note...VW got rid of it altogether as part of a package of modes for hydraulic lifters. I found years ago just how critical it is to the actual oil cooler relief valve functioning reliably. Its a pain in the back side.Ray |
Ray can you find any links to discussions about replacing the oil control valve spring with a solid rod? I cant find anything. What was the result? Any downsides? |
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SGKent
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Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Tue May 29, 2018 8:10 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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Ralph, you appear to be entering a stage of denial. Sit back for a second. The bearings should have a clearance of about .002" +/-. Imagine how much oil would escape the bearings if you were running 3 times that at .006". You aren't a drag racer doing a quarter mile between rebuilds. When the pump wears it does so mostly on end-play. You can see this on T1 pumps when the gears eat into the steel plate which wears. Those folks can replace the steel plate or mill it flat again. About 10 years ago I bought every T4 oil pump I could find. About 20% of them were worn beyond repair. The others went to Phil who machined them so they were back to about .0015" to .002" end play. Most were up to .005" to .006" before he corrected that. Think how much oil pressure was leaking around the gears. Lash opens up too a little and that cannot be brought back without new gears, or expensive plating processes. Oil can't escape the lash unless the shaft allows wobble, or it chatters. The main key is tightening up the endplay. This is best done with an end mill. The idle shaft should be pinned also.
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RalphWiggam
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Joined: February 02, 2018
Posts: 906
Location: SouthEast
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| Posted: Tue May 29, 2018 8:32 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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| SGKent wrote: |
| Ralph, you appear to be entering a stage of denial. Sit back for a second. The bearings should have a clearance of about .002" +/-. Imagine how much oil would escape the bearings if you were running 3 times that at .006". You aren't a drag racer doing a quarter mile between rebuilds. When the pump wears it does so mostly on end-play. You can see this on T1 pumps when the gears eat into the steel plate which wears. Those folks can replace the steel plate or mill it flat again. About 10 years ago I bought every T4 oil pump I could find. About 20% of them were worn beyond repair. The others went to Phil who machined them so they were back to about .0015" to .002" end play. Most were up to .005" to .006" before he corrected that. Think how much oil pressure was leaking around the gears. Lash opens up too a little and that cannot be brought back without new gears, or expensive plating processes. Oil can't escape the lash unless the shaft allows wobble, or it chatters. The main key is tightening up the endplay. This is best done with an end mill. The idle shaft should be pinned also. |
Denial about what exactly? I just said that my oil pressure is well within (almost perfect) to the bentley spec of 42psi at 2500rpm at 158deg. What Im reaching for is beyond published specs. Id like to see 12psi or so per 1000rpm at full operating temp. Maybe thats not achievable, and I have no issue going back through my oil pump if need be. Furthermore, as any rational person would do, I will eliminate the easy variables first. That is what Im currently doing.
Do you have any feedback on the pros and cons on removing the second oil control valve on early bus cases? Seems most people say to use a rod so it stops opening. Bentley says it might cause increased oil consumption from oil spraying out of the bearings into the bottoms of the cylinders. I can deal with that if it is the only downside. |
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Tue May 29, 2018 8:50 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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| RalphWiggam wrote: |
| SGKent wrote: |
| Ralph, you appear to be entering a stage of denial. Sit back for a second. The bearings should have a clearance of about .002" +/-. Imagine how much oil would escape the bearings if you were running 3 times that at .006". You aren't a drag racer doing a quarter mile between rebuilds. When the pump wears it does so mostly on end-play. You can see this on T1 pumps when the gears eat into the steel plate which wears. Those folks can replace the steel plate or mill it flat again. About 10 years ago I bought every T4 oil pump I could find. About 20% of them were worn beyond repair. The others went to Phil who machined them so they were back to about .0015" to .002" end play. Most were up to .005" to .006" before he corrected that. Think how much oil pressure was leaking around the gears. Lash opens up too a little and that cannot be brought back without new gears, or expensive plating processes. Oil can't escape the lash unless the shaft allows wobble, or it chatters. The main key is tightening up the endplay. This is best done with an end mill. The idle shaft should be pinned also. |
Denial about what exactly? I just said that my oil pressure is well within (almost perfect) to the bentley spec of 42psi at 2500rpm at 158deg. What Im reaching for is beyond published specs. Id like to see 12psi or so per 1000rpm at full operating temp. Maybe thats not achievable, and I have no issue going back through my oil pump if need be. Furthermore, as any rational person would do, I will eliminate the easy variables first. That is what Im currently doing.
Do you have any feedback on the pros and cons on removing the second oil control valve on early bus cases? Seems most people say to use a rod so it stops opening. Bentley says it might cause increased oil consumption from oil spraying out of the bearings into the bottoms of the cylinders. I can deal with that if it is the only downside. |
Ralph. Maybe I am reading something into this that isn't there but it seems to me that you are looking at a solid rod for the control valve to try to find more pressure. It would be most appropriate to have the oil pump blueprinted first.
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RalphWiggam
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Joined: February 02, 2018
Posts: 906
Location: SouthEast
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| Posted: Tue May 29, 2018 9:25 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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| SGKent wrote: |
| RalphWiggam wrote: |
| SGKent wrote: |
| Ralph, you appear to be entering a stage of denial. Sit back for a second. The bearings should have a clearance of about .002" +/-. Imagine how much oil would escape the bearings if you were running 3 times that at .006". You aren't a drag racer doing a quarter mile between rebuilds. When the pump wears it does so mostly on end-play. You can see this on T1 pumps when the gears eat into the steel plate which wears. Those folks can replace the steel plate or mill it flat again. About 10 years ago I bought every T4 oil pump I could find. About 20% of them were worn beyond repair. The others went to Phil who machined them so they were back to about .0015" to .002" end play. Most were up to .005" to .006" before he corrected that. Think how much oil pressure was leaking around the gears. Lash opens up too a little and that cannot be brought back without new gears, or expensive plating processes. Oil can't escape the lash unless the shaft allows wobble, or it chatters. The main key is tightening up the endplay. This is best done with an end mill. The idle shaft should be pinned also. |
Denial about what exactly? I just said that my oil pressure is well within (almost perfect) to the bentley spec of 42psi at 2500rpm at 158deg. What Im reaching for is beyond published specs. Id like to see 12psi or so per 1000rpm at full operating temp. Maybe thats not achievable, and I have no issue going back through my oil pump if need be. Furthermore, as any rational person would do, I will eliminate the easy variables first. That is what Im currently doing.
Do you have any feedback on the pros and cons on removing the second oil control valve on early bus cases? Seems most people say to use a rod so it stops opening. Bentley says it might cause increased oil consumption from oil spraying out of the bearings into the bottoms of the cylinders. I can deal with that if it is the only downside. |
Ralph. Maybe I am reading something into this that isn't there but it seems to me that you are looking at a solid rod for the control valve to try to find more pressure. It would be most appropriate to have the oil pump blueprinted first. |
That is partially true. I'm very interested in the research around this second valve. It seems like a pretty rare item to have and what discussions I can find about it say to make it static. I want to know why. There are probably thousands of late cases out there without this valve running solid lifters with no issue. Why shouldnt I make my case this way? |
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Volswagon
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Joined: December 29, 2009
Posts: 299
Location: Knoxville, TN
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| Posted: Tue May 29, 2018 9:46 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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I suspect the rod is meant to limit the movement of the piston instead of prevent it.
Since I've not had a pressure gauge on mine I don't know the max. pressure it allowed. I know it kept the motor going for 228K miles.
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SGKent
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Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Tue May 29, 2018 10:19 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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actually it isn't "rare." Almost every bay whether upright or pancake has two valves. The late 1977 - 1978 engine and later dropped it. Don't assume it is for the better. Those late engines all have problems getting initial oil pressure when they sit for a long time because any air in the system has no place to go but turn into a froth. In your engine it gets pushed out the 2nd valve rather than being sent back to the oil pump to froth some more.
The valve at the end of the oil gallery also prevents over pressure situations from splitting the seams on your oil cooler among other things.
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RalphWiggam
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Joined: February 02, 2018
Posts: 906
Location: SouthEast
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| Posted: Tue May 29, 2018 11:37 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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| SGKent wrote: |
actually it isn't "rare." Almost every bay whether upright or pancake has two valves. The late 1977 - 1978 engine and later dropped it. Don't assume it is for the better. Those late engines all have problems getting initial oil pressure when they sit for a long time because any air in the system has no place to go but turn into a froth. In your engine it gets pushed out the 2nd valve rather than being sent back to the oil pump to froth some more.
The valve at the end of the oil gallery also prevents over pressure situations from splitting the seams on your oil cooler among other things. |
I thought they dropped the second valve when they went to hydraulic lifters. Wouldnt the main relief valve prevent the oil cooler or filter from exploding (assuming it was working properly)?
Last edited by RalphWiggam on Tue May 29, 2018 11:43 am; edited 1 time in total |
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SGKent
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Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Tue May 29, 2018 11:40 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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| RalphWiggam wrote: |
| SGKent wrote: |
actually it isn't "rare." Almost every bay whether upright or pancake has two valves. The late 1977 - 1978 engine and later dropped it. Don't assume it is for the better. Those late engines all have problems getting initial oil pressure when they sit for a long time because any air in the system has no place to go but turn into a froth. In your engine it gets pushed out the 2nd valve rather than being sent back to the oil pump to froth some more.
The valve at the end of the oil gallery also prevents over pressure situations from splitting the seams on your oil cooler among other things. |
I thought they dropped the second valve when they went to hydraulic lifters. |
I believe all bay cases were double valve from 1968 to part way thru 1977.
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udidwht
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Joined: March 06, 2005
Posts: 3779
Location: Seattle, WA./ HB, Ca./ Shizuoka, Japan
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| Posted: Tue May 29, 2018 11:43 am Post subject: Re: Sealing rings at top/bottom of cylinders |
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| SGKent wrote: |
Ray you have posted here before that you do not own a bus. I encourage you to buy one and restore it. Drive it awhile and see the difference between it and a bug etc. The one place you will get bitten in a bus is highway speeds on a hot day then pulling a grade or pushing a headwind. Your oil WILL get very hot, typically 250 F to 260 F. You can compare viscosities on this chart from the RAtwell page. The viscosity of 20w50 @ 212F is approximately the same as SAE 30 @ at 160F. Richard goes into a lengthy discussion about buses and oils on that page. The thermal question asked in this thread is valid for a bus. No one in a bug. 411 or 914 comes even close to the heat a bus generates unless they are racing around a track near wide open for hours.
Richard's numbers came directly from Valvoline. FWIW the oil that isn't used gets dumped back to the sump (or recirculated in a late case). When the oil is hot the pressure is so low that no oil is bypassing the cooler. If cold oil bypasses the cooler why would that bother anyone? Cool oil is the goal. The 20w50 is used because it holds the 10 PSI /1000 when it is 250F - 260F that a bus can see (and higher if pushed harder). In the case of this thread - he is seeing low pressures 40 degrees lower than that. Like you I suspect that the pump is worn. I also don't recall if plasti-gauge was used on all the bearings. I am not suggesting every bus needs 20w50 oil but when it is 108F here and we are driving 50 mph the oil is very thin. Add a long grade and it gets even thinner.
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If I'm not mistaken in all the testing Jake did with the T-4 and buses 20w/50 viscosity fared the best overall. He did not approve of running 30 weight oils in a bus (unless you were cold climate). In fact he told me once....They thin like piss with bus heat.
_________________
1972 Westy Hardtop/Type-4 2056cc
96mm Biral AA P/C's~7.8:1CR
Headflow Masters New AMC 42x36mm heads w/Porsche swivel adjusters
71mm Stroke
73 Web Cam w/Web solids
Dual 40mm IDF Webers - LM-2 - 47.5 idles/125 mains/190 air corr./F11 tubes/28mm Vents - Float height 10.45mm/Drop 32mm
Bosch SVDA w/Pertronix module (7.5 initial 28 total @ 3400rpm)
Bosch W8CC plugs
Pertronix Flamethrower 40K coil
S&S 4-1 w/Walker QP 17862
3 rib 002 Trans
185R14 Hankook tires |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50338
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| Posted: Tue May 29, 2018 1:12 pm Post subject: Re: Sealing rings at top/bottom of cylinders |
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| udidwht wrote: |
| SGKent wrote: |
Ray you have posted here before that you do not own a bus. I encourage you to buy one and restore it. Drive it awhile and see the difference between it and a bug etc. The one place you will get bitten in a bus is highway speeds on a hot day then pulling a grade or pushing a headwind. Your oil WILL get very hot, typically 250 F to 260 F. You can compare viscosities on this chart from the RAtwell page. The viscosity of 20w50 @ 212F is approximately the same as SAE 30 @ at 160F. Richard goes into a lengthy discussion about buses and oils on that page. The thermal question asked in this thread is valid for a bus. No one in a bug. 411 or 914 comes even close to the heat a bus generates unless they are racing around a track near wide open for hours.
Richard's numbers came directly from Valvoline. FWIW the oil that isn't used gets dumped back to the sump (or recirculated in a late case). When the oil is hot the pressure is so low that no oil is bypassing the cooler. If cold oil bypasses the cooler why would that bother anyone? Cool oil is the goal. The 20w50 is used because it holds the 10 PSI /1000 when it is 250F - 260F that a bus can see (and higher if pushed harder). In the case of this thread - he is seeing low pressures 40 degrees lower than that. Like you I suspect that the pump is worn. I also don't recall if plasti-gauge was used on all the bearings. I am not suggesting every bus needs 20w50 oil but when it is 108F here and we are driving 50 mph the oil is very thin. Add a long grade and it gets even thinner.
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If I'm not mistaken in all the testing Jake did with the T-4 and buses 20w/50 viscosity fared the best overall. He did not approve of running 30 weight oils in a bus (unless you were cold climate). In fact he told me once....They thin like piss with bus heat. |
When I did some testing 5'ish years ago, of the oils I tested 20w50 ran the hottest and 30wt the coolest, with the difference in temperature at the top of a long grade being about 25-30° cooler for the 30wt, thus the viscosities in actually use for the two oils would be about the same. A cooler oil can also remove more heat from the bearings and cylinders than a hotter oil. Also by API standard a straight weight oil can have no viscosity modifiers (which can break down in the heat and long usage) nor are they restricted in the amount of ZDDP they can run.
I ran 30wt in all my rigs, watercooled and air cooled for many decades during the heat of summer and it never occurred to me that it might not be doing a fine job. Never thought or heard different until I first signed on to The Samba. |
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