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My solution to the plugged cam oiling dilemma was born when I first rebuilt the 930 ten years ago. I noticed that the very end ( nearest the driver, back of the engine ) oil holes were plugged with the oil cap nut. What I did was take those plugs out ( one from each side ) and replace them with banjo fittings then ran a tube to the front of the engine, dropping out of the shroud at the back. Letting those tubes drop and then installed brass compression ells with caps. When I would do my oil changes I would take the plug from the ig-coil and crank the engine for a few seconds and the oil would pump out of my cam drain tubes. What this accomplished was removing any crap that had built up in the ends of the cam oiling tubes; obviously a ľ inch hole flows better than a pin-hole when one is wanting to remove crud.




munchovie
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Last edited by wmunchovie; 12-07-2007 at 06:12 PM.. Reason: spelling
Old 12-07-2007, 06:09 PM
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AYGLASS: I agree with you 100% on the B&B replacement oil sump tank; not only does it not allow for filtering, it does not allow for turbo blow-by gasses to escape into to the air intake housing just on top of the CIS plate via the factor breather vent in the sump tank. B&B had a nice set of headers but they should have, in my opinion, created a set of headers that would have allowed the stock sump tank to be used. Moreover, the sump tank acts as a buffer; during periods of high boost the oil is allowed to accumulate in the tank prior to being scavenged by the turbo scavenge pump for minor cooling and turbo bearing flood ( in my opinion ).
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Old 12-07-2007, 08:01 PM
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I spent some time going through this thread and have a couple of thoughts to share. I’m not a CSI investigator but I have extensive background in turbos and tend to get unhinged when every engine problem on a turbocharged engine eventually gets blamed on the turbocharger.
The thread starts with describing an extreme thermal excursion for the entire engine. Now in this situation the turbo is happily idling away and not exposed to conditions to form varnish much less hard coke. However being an air-cooled engine if the oil is at an excessive temperature so are the head temperatures.
Everyone who has experience with non turboed air-cooled Porsches, aircraft or the lowly VW knows you will find coke chunks in the oil strainers. Without turbos, how can this be?
Because they are air-cooled and the coke is being formed in the extreme temperature areas localized around the exhaust valves and moving outward as the mineral based oils are being cooked. There is also the very real problem of all turboed engines; blow by. This forms similar accumulations in the vent hoses, oil tank, etc.
I pose one more question for you. If these chunks shown in the initial posting were formed in the turbo bearings, how did they get through TWO close tolerance pumps, the oil scavenge then the oil pressure pump without being pulverized?
I think these were formed in the cooling rail oil delivery path during repeated running and hot shutdown extremes throughout the life of this motor. This last extreme was the killer.
If you can’t except coke, obvious you can’t, use synthetic oil, as do all the gas turbines in the world.
Marty

Last edited by copbait73; 12-08-2007 at 02:09 PM..
Old 12-08-2007, 01:52 PM
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Hey Marty,

So how do you explain the coke found in the post-turbo screen that I installed? Are you suggesting that the coke was created somewhere else and passed through the close-tolerance turbo bearing to get to the strainer?

I'll let Dave speak to his "thermal excursion". My engine has not been extremely hot and has not been shut down after a hard run without a cool down period so I would say that my coke formed within normal operating parameters.

I can't argue the broad case that coke isn't found under other circumstances. I can only argue that in my case it was found post-turbo and that coke is implicated in the lubrication problems with my engine. Looking at the oil flow diagram, oil returning from the heads passes through the oil filter before returning to the tank and oil from the turbo doesn't. My theory was that this was a design flaw with this unfiltered tank and return so I put a screen inline with the turbo and collected coke bits.

Simply put, I can't rule out the universe of other ways that coke could have arrived in my cam spray bar. I can only point out a likely source that does indeed create coke bits. I've addressed this source, but of course I will continue to look for any indication that I have another source.

As to the synthetic oil, I was using synthetic at the time of the incident. I realize that the coke could have been formed before I switched to synthetic and then broken loose, but all of us (excepting those who have done a complete rebuild and replaced oil coolers etc) have used dino oil in our cars because that's what was available and factory recommended when these cars were born. My car is proof that synthetic oil, later in the engine's life does not make one immune to issues with coke. As you suggest, I may go synthetic from the beginning with a new rebuild. That seems prudent given that turbo engines are more "thermally challenged" than NA engines.
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'86 930 Kokeln IC, K27-7200, SC cams, GHL headers, Fabspeed muffler, Short R&P , misc other mistakes made...
Old 12-08-2007, 04:25 PM
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Just wanted to point out that it is possible that when you switched to synth oil it possibly released coke from the outlet of the turbo.

Anyway, the screen is an excellent idea providing it is cleaned often (depending on how often the car is used).
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 12-08-2007, 11:37 PM
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Quote:
Originally Posted by copbait73 View Post
Iím not a CSI investigator but I have extensive background in turbos and tend to get unhinged when every engine problem on a turbocharged engine eventually gets blamed on the turbocharger.
Well, get unhinged because this camshaft failure was due coking in the turbocharger.

Quote:
Originally Posted by copbait73 View Post
The thread starts with describing an extreme thermal excursion for the entire engine. Now in this situation the turbo is happily idling away and not exposed to conditions to form varnish much less hard coke. However being an air-cooled engine if the oil is at an excessive temperature so are the head temperatures.
So you are telling me that the ambient temperature of a turbo bearing shaft "happily idling away" is lower than the oil (230 degrees) that's being circulated in this situation? Remember, the reason for the elevated temps in the engine oil is due to the volume of oil being circulated through the engine is insufficient. Same applies for the turbocharger. Varnish is going to generated on the turbocharger shaft in a condition such as this with dino oil.


Quote:
Originally Posted by copbait73 View Post
Everyone who has experience with non turboed air-cooled Porsches, aircraft or the lowly VW knows you will find coke chunks in the oil strainers. Without turbos, how can this be?
Who said it can't?

Quote:
Originally Posted by copbait73 View Post
Because they are air-cooled and the coke is being formed in the extreme temperature areas localized around the exhaust valves and moving outward as the mineral based oils are being cooked. There is also the very real problem of all turboed engines; blow by. This forms similar accumulations in the vent hoses, oil tank, etc.
The used oil delivered by the DRY SUMP PUMP is returned to the OIL FILTER before going into the holding tank. So anything gathered from the engine's sump is going to be filtered before residing in the holding tank. The turbo sump pump is another matter all together.

Coke doesn't just magically appear. Elevated oil temps go through a metamorphosis. The coke chunks I found in the valve train feed tubes had hardened over time and the exposure to brake cleaner which I tried to use to clear the tubes (didn't work). Also, the appearance of the "chunks" looks like they attached themselves to each other over time. Before becoming coke, oil becomes a very tacky substance and I am sure that is how the pieces became attracted.

Quote:
Originally Posted by copbait73 View Post
I pose one more question for you. If these chunks shown in the initial posting were formed in the turbo bearings, how did they get through TWO close tolerance pumps, the oil scavenge then the oil pressure pump without being pulverized?
Like I said, The coke did not have to appear immediately on the turbo shaft, but the metamorphosis of oil to varnish to tar will easily get through the turbo sump pump.

Quote:
Originally Posted by copbait73 View Post
I think these were formed in the cooling rail oil delivery path during repeated running and hot shutdown extremes throughout the life of this motor. This last extreme was the killer.
This was a split case freshly rebuilt engine (about 3K miles since rebuild), thoroughly cleaned... I blame the failure on two factors. Web Cams would not warranty the cams if Syn Oil was used to lubricate the engine, so I had to use dino oil. Two, the current dino motor oils are lacking in the proper minerals for the early engines running this type of valve train mechanism.
I did not shut the engine down hot. The engine was shut down after driving it at highway speeds to bring the temps down.


Quote:
Originally Posted by copbait73 View Post
If you canít except coke, obvious you canít, use synthetic oil, as do all the gas turbines in the world.
Marty
The reason we (or I) can not accept the coke is obvious. It was a poor design on Porsche's behalf to have used oil returning from the turbocharger to the main sump tank UNFILTERED.
Two, it is a poor design to have the top end lubricating system OPEN LOOP. Once a particle such as coke gets in there, it's just a matter of time before it gets into the feed hole and begins to clog it.
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'85 930 Factory Special Wishes Flachbau
Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P
Old 12-09-2007, 05:32 AM
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If one's 930 utilizes the factory sump tank which includes the filter screen as shown below then the oil leaving the turbo sump tank, entering the turbo scavenge pump will, in fact be, filtered; the only particles that can get thru the screen filter are ones which have a physical size smaller than the screen grid matrix size.

munchovie

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Old 12-09-2007, 07:38 AM
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Dave:
Thank you for the additional information. Since you challenge my statements I find it interesting your discussion moves from being responsible for, to being a victim of, several poor design features that compounded to engine failure in only 3,000 miles of street driving. This only brings me to three conclusions:
1) You conducted or paid someone for a dirty engine rebuild on a 20 year old engine (you don’t give mileage). Don’t feel bad it happens very frequently, turboed or not.
2) In combination, you cooked your engine. You are responsible for keeping your engine in normal operating parameters regardless the circumstances. If you had not allowed the engine core to reach extreme temperatures the oils viscosity would not have broken down. This happens too, turboed or not.
3) You are in denial about these two issues but watch out on the second one, most modern engines the ECM will tell on you. .
Marty

Last edited by copbait73; 12-09-2007 at 10:57 AM..
Old 12-09-2007, 08:33 AM
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Too funny!

It is amazing to me how some people tend to treat anything that comes out of Porsche or some piece of machinery as some sort of sacred monolith. Just for your sense of getting the facts straight, I rebuilt the engine. I have rebuilt many engines before of all types and countries of origin. The "thermal stress" you refer to occurred at the Port of Entry from Canada at Port Huron. Some months after 9/11 all points of entry to the U.S. became nightmares for people coming back into the country. The highway backed up for several miles with no where to go, jackasses were driving on the breakdown lanes risking people's safety and welfare. If you think I'm going to pull over into situation and risk my safety or the safety of others, forget it. I didn't peg the oil temp gauge, but I knew that the oil temp was beyond normal operating parameters.

Geez......If you don't know the facts, don't offer some ridiculous theories based on your predjudices.
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'85 930 Factory Special Wishes Flachbau
Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P
Old 12-09-2007, 09:04 AM
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Dave:
My thoughts are far from the Porsche engine being any sacred monolith, maybe you are projecting? As to the facts they are yours and they lead to logical conclusions which are not turbo engine specific. All the rest is diversion.
Is WebCams giving you warranty?
Marty
Old 12-09-2007, 10:52 AM
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Freud?

First Marty suggests Dave is in "Denial" and then he suggests Dave is "Projecting". I thought this was an engineering discussion. Dave and I have cars that had issues, then someone takes issue with our issues. I had better dust off my M.A. in Psychology... it looks like it's suddenly applicable to our discussion.

I tend to agree with Nathan. I believe that the coke formed in the turbo over the years of using dino oil with the P.O. and that the change to synthetic broke them loose. Many of the chunks are shiny on an inside radius.
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'86 930 Kokeln IC, K27-7200, SC cams, GHL headers, Fabspeed muffler, Short R&P , misc other mistakes made...
Old 12-09-2007, 11:15 AM
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Quote:
Originally Posted by ayglass View Post
First Marty suggests Dave is in "Denial" and then he suggests Dave is "Projecting". I thought this was an engineering discussion. Dave and I have cars that had issues, then someone takes issue with our issues. I had better dust off my M.A. in Psychology... it looks like it's suddenly applicable to our discussion.

I tend to agree with Nathan. I believe that the coke formed in the turbo over the years of using dino oil with the P.O. and that the change to synthetic broke them loose. Many of the chunks are shiny on an inside radius.
Thank you!

I spoke with a 930 engine builder/racer (read posts), he has advised and revised the oil return lines from the turbo sump to incorporate an oil filter. According to him (not projecting), it has improved the reliability of the oil system dramatically.
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'85 930 Factory Special Wishes Flachbau
Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P
Old 12-09-2007, 11:22 AM
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Quote:
Originally Posted by wmunchovie View Post
If one's 930 utilizes the factory sump tank which includes the filter screen as shown below then the oil leaving the turbo sump tank, entering the turbo scavenge pump will, in fact be, filtered; the only particles that can get thru the screen filter are ones which have a physical size smaller than the screen grid matrix size.

munchovie

My car didn't have one of these. Does anybody here have this exact one?

Mine was similar but not the same & definitely does not have a filter screen. It was definitely a Porsche part.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg

Last edited by NathanUK; 12-09-2007 at 01:57 PM..
Old 12-09-2007, 01:54 PM
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Dave:
Ok, so WebCam denies warranty. Somehow Iím not surprised.
Andy:
Yes, this is a technical discussion. I specifically addressed my conclusions to Daveís situation and statements. They did not address the possible root cause(s) of your engine failure or the realitive merits of a post turbo sump filter. Given the existing engine system the filter has merits worth considering but only in light of possible drawbacks.
Here, does this work? Yes, you are both correct in all your conclusions. Now you have heard what you wish to hear.
Marty
Old 12-09-2007, 02:48 PM
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Quote:
Originally Posted by NathanUK View Post
My car didn't have one of these. Does anybody here have this exact one?

Mine was similar but not the same & definitely does not have a filter screen. It was definitely a Porsche part.
The diagram of the turbo sump tank came from the Porsche Turbo workshop manual; section 21 - 12 "Turbocharger oil supplyĒ. I know that the 76 Turbo Carrera did not have this type tank, it was more like a long candy bar. I also know that an 84 turbo did not have this model from one I just checked - I am going to check a 77, 80 and 85 and will post later when I find out.

A note worth mentioning: if one had a filter and did not clean it then the turbo would backup with oil and the back pressure would force oil it out the bearing race and into the cold and hot side of the turbo; I have rebuilt several turbos and have seen the 'coke' caked in the bearing housing and hot wheel side.

Obviously, the best thing to do is keep oil changed regularly and let the turbo cool down after ďhot sessionsĒ thereby avoiding any substantial 'coking'. Couple the facts that K27 can spool up to 90,000 rpm and the turbo hot side is like a blazing furnace, one should realize that the oil passing over the bearing is going to get pretty toasty. This hellatious heat obviously breaks down the lubricants ability to properly do itís job. Another idea: has anyone ever run an engine super hot after blowing a radiator hose then tried to change the oil? Gooey black yuck.


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Old 12-09-2007, 04:08 PM
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