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Clogged Spray Bar autopsy

Thought I'd post some pics of my recent teardown and reassembly of the engine. Some background on the set of circumstances I think caused the disaster. When I was moving back to Wisconsin from the Boston area, I decided to take the "scenic" route through Canada, PoE Port Huron, Michigan then through the U.P. of Michigan down to Wisconsin. Well, the port of entry for Port Huron was very congested. I was stuck in traffic for a l-o-n-g time and the oil temps got very high. If I was using synthetic oil, it may have given a bit more margin of error in the temp department. But using Web Cams, they said syn oils were taboo....
Anyway, the black specks in the white background are the pieces I found on the spray bar at the holes that spray oil on the valve train. They are black and carbon like, almost like charcoal. They do break when pressure is applied. I think it's the byproduct of the oil overheating, yes??

The rocker arms you see are from cylinders #6 and #5. Cylinder heads #1 thru 4 escaped the carnage. This all happened over a period of 300 miles with the some terrible noises developing over the last 50 miles. Limped home and began the long process of removal/teardown.



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Dave
'85 930 Factory Special Wishes Flachbau
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Old 10-02-2007, 07:20 AM
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OH...THE HUMANITY! So going forward, Dave, what are your thoughts on the dreaded oil debate? Also, what's in store for the engine? Quick and dirty tear down and rebuild - or going kookoo?
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back in the saddle: '95 993 - just another black C2
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Old 10-02-2007, 07:47 AM
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Angry

This is very interesting. I am doing the exact same rebuild now. I just buttoned up the engine and I'm getting it ready to reinstall. For me, #2 intake lost lubrication and the spray bar was the culprit. I forced solvent through the spray bar from end to end so I did not save the pieces that clogged the port.

I had switched to Mobil-1 from 20-50 two oil changes prior to the carnage. I've suspected this was a mistake and thought some debris might have been dislodged by the oil type change. Since the discussion of ZDDP, I have found that I can get Rotella-T locally. I am going back with Rotella and changing it weekly!







Thoughts?
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Andy Glass
'86 930 Kokeln IC, K27-7200, SC cams, GHL headers, Fabspeed muffler, Short R&P , misc other mistakes made...
Old 10-02-2007, 08:05 AM
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I thought this was/is a clever solution. These things do have a history of getting clogged. I thought maybe the next time I had my engine out, I'd make this change in case I ever wanted to remove the spray bar:
cam spray bar plug replacment
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 10-02-2007, 08:10 AM
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And not to hi-jack Dave's thread with oil controversy, I'm running Brad Penn 20W-50 and have been very pleased. I can get it for $40.00 a case. On my next oil change, I plan to have an oil analysis done.

Prior to that, I was running Rotela "T" synthtetic 5W-40 and found it to too thin for my climate. Oil temps were deffinately higher.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 10-02-2007, 08:19 AM
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Quote:
Originally Posted by sand_man View Post
OH...THE HUMANITY! So going forward, Dave, what are your thoughts on the dreaded oil debate? Also, what's in store for the engine? Quick and dirty tear down and rebuild - or going kookoo?
The engine is back together, replaced the spray bars, put the damaged rockers back in ......just kidding, flushed the system as best I could, new rockers, elephant feet, rocker shafts and reinstalled the original SC cam the Special Wishes people had in there in the first place. Later, I'll using Dougherty 964 cams in the car, but now, I just want to drive it!

Don't get me wrong, the extreme oil temperatures were the culprit. I really do feel the synthetic oils give you that extra margin of safety on the turbocharger bearing and valve train when it comes to events like this.

These engines ARE not designed for low engine speeds. Never lug the engine below 2K RPM and never, never allow yourself to sit stuck in a traffic jam for extended periods of time. There just isn't enough oil volume going to the heads to keep the temps down.
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'85 930 Factory Special Wishes Flachbau
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Last edited by WERK I; 10-02-2007 at 03:12 PM.. Reason: forget a segment
Old 10-02-2007, 03:07 PM
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That same mod had already been done on my cam towers. Luckily it was because I found huge junks of carbon in my spray bars, even after the towers had a good bath.

Quote:
Originally Posted by sand_man View Post
I thought this was/is a clever solution. These things do have a history of getting clogged. I thought maybe the next time I had my engine out, I'd make this change in case I ever wanted to remove the spray bar:
cam spray bar plug replacment
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1979 Porsche 930: 3.4L, SC cams, Twin plug, Leask WUR, Custom SSI turbo exhaust, Tial WG, K27HFS, and we can't forget the Zork (short lived depending on my homeowners assoc.)
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Old 10-02-2007, 04:12 PM
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So how to we keep these small bits of carbon from getting into our spray bars? A small filter on the turbo return line? A "turbo timer" to keep the beast running for a while after it's parked? I for one am very motivated to keep this from happening again.

Note the look of motivation on my face... or exhaustion...

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Andy Glass
'86 930 Kokeln IC, K27-7200, SC cams, GHL headers, Fabspeed muffler, Short R&P , misc other mistakes made...
Old 10-02-2007, 10:18 PM
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Oil from the turbo drains to it's own little sump tank, then gets sucked to the turbo scavenge pump where it gets pumped on to the main oil tank without going through the oil filter, right?
Or does the oil from the scavenge pump get pushed through the oil filter? I think only the oil coming from the scavenge side of the engines oil pump goes through the oil filter.

So maybe this carbon thats clogging the spray bars is coming from coked or burnt oil from the turbo bearing.
Maybe this is more reason to use synthetic oil and let it idle cool down a minute or so after driving.

Might be a good idea to take off the turbo sump and see if you can rinse any little burnt oil carbon chunks out of it...
Old 10-02-2007, 10:20 PM
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Quote:
Originally Posted by JFairman View Post
Oil from the turbo drains to it's own little sump tank, then gets sucked to the turbo scavenge pump where it gets pumped on to the main oil tank without going through the oil filter, right?
Or does the oil from the scavenge pump get pushed through the oil filter? I think only the oil coming from the scavenge side of the engines oil pump goes through the oil filter.

So maybe this carbon thats clogging the spray bars is coming from coked or burnt oil from the turbo bearing.
Maybe this is more reason to use synthetic oil and let it idle cool down a minute or so after driving.

Might be a good idea to take off the turbo sump and see if you can rinse any little burnt oil carbon chunks out of it...
The turbo sump oil goes back into the oil tank unfiltered.
The main tank oil is filtered "before" it is fed to the engine on the pre-964 engines. The problem I see with their logic is when the engine is cold, the viscosity of the oil is high. The oil filters high a pressure spring bypass that allows the oil to go to the engine unfiltered, relatively speaking. Porsche found its wisdom later by filtering before AND after with the 964's.

The other problem I see is the top end lubrication is open loop. If in the unlikely event that any particles get up there, they have no where to go. A ticking time bomb, IMHO.
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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

Last edited by WERK I; 10-07-2007 at 06:42 AM.. Reason: oops! meant open loop
Old 10-03-2007, 06:41 AM
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Regarding the additional 964 oil filter, I think it was DonE that did this to his highly modified '79 Turbo. I don't think his pictures are still visible in this thread though:
http://forums.rennlist.com/rennforums/showthread.php?t=241512
I think if I ever ran an extra oil cooler in the front valence, I might consider ditching the engine cooler for the extra filter. There are also a few other basic mods needed to make it work, but it can be done without too many headaches.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 10-03-2007, 07:12 AM
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Would plumbing a small filter on the output side of the turbo scavenge pump make sense? Do I need to worry about pressure and flow issues with that line? It would seem that it's a small amount of oil relative to the main filter.
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'86 930 Kokeln IC, K27-7200, SC cams, GHL headers, Fabspeed muffler, Short R&P , misc other mistakes made...
Old 10-03-2007, 10:17 AM
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On my 930 engine, I ditched the engine oil cooler in favor of a 993 filter console. I did it for the very reason discussed in this thread -- any contamination that makes it into the tank from any source is going to go right to the main oil gallery. That made me nervous. The problem is, a modified 930 will generate even more heat than a stock one, so the addition of extra cooling capacity becomes even more important.

To add this filter, you can buy almost all of the components from Smart Racing Products. I used a factory 993 oil filter console, which has the filter mounted vertically. The 964 turbo filter console (which also works) has a 15 degree angle to it, perhaps to make it easier to remove the filter. But I have no trouble getting mine on and off. Either filter will just bolt on to the engine. But it takes a little work to modify the ducting. It's necessary to seal off the air flow that previously ventilated the engine mounted cooler, and to preserve the separation between top and bottom of the engine compartment. To do this, I made a couple of sheet metal pieces -- one to seal off the channel that diverts air from the fan to the cooler, and one that sealed off the end of the #6 cylinder head. I then gutted an old oil cooler and used it to provide the seal for the engine compartment -- it already fit so nicely that I couldn't see making a whole new piece just for that.

To cover for the loss of cooling (and increased heat load from engine mods) I added two coolers up front -- a fender mounted cooler with a fan and a large center cooler. On a recent 90 degree track day here, engine temps never rose above 205 F.

Here are some pics of my setup:


Old 10-03-2007, 10:38 AM
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Quote:
Originally Posted by ayglass View Post
Would plumbing a small filter on the output side of the turbo scavenge pump make sense? Do I need to worry about pressure and flow issues with that line? It would seem that it's a small amount of oil relative to the main filter.

Seems to me a small inline cleanable/serviceable fine screen filter like some of the anodized aluminum inline AN fitting fuel filters you see in a Jegs or Summit Racing catalog would be a good thing and wouldn't impede oil flow either.
Old 10-03-2007, 10:49 AM
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The main tank oil is filtered "before" it is fed to the engine on the pre-964 engines.
I don't think you have that right. AFAIK the oil is only filtered when it leaves the engine by running through the filter at the top of the tank before it goes back into the bottom of the tank for storage.
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Old 10-03-2007, 03:43 PM
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Can anyone confirm which is right?
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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 10-06-2007, 01:43 AM
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Hey Nathan,

I looked at a 911 oil flow diagram last night and it appears that oil is only filtered on return to the tank from the engine. The turbo scavenge pump appears to return directly to the tank unfiltered. I felt around the bottom of my tank through the drain hole and found some carbon bits that look like the ones Dave recovered from his spray bar. I washed out the tank.

While it appears that gravity might separate this trash from the engine's oil supply most of the time, it obviously doesn't prevent this kind of failure. I would like to believe that the oil tank would be considered a "clean zone". I am going to pursue some kind of filter/screen on that scavenge pump return line. This appears to be a design weakness on the Turbo.
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Last edited by ayglass; 10-06-2007 at 10:34 AM..
Old 10-06-2007, 09:19 AM
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Nathan,

Andy is right, but in reading the quote from WERK-1, I think he meant the same thing: on a 911 or 930, the oil is filtered only as it enters the tank. This occurs when oil flows back into the tank from the engine -- either directly or from the front-mounted oil cooler (if the thermostat sent it there first). Oil from the turbo scavenge pump goes right into the tank unfiltered. Any oil (or dirt) flowing from the tank to the engine goes first to the pressure side of the oil pump, then upward to the thermostat housing for the engine-mounted oil cooler (and perhaps through the cooler), then into the main oil gallery and right into the crankshaft bearings.

I don't know about putting a filter on the turbo scavenge line. It might work, but you might want to be careful that whatever filter is placed there doesn't cause a restriction that might inhibit scavenging. The nice thing about adding the filter as I did is that it catches any dirt that may enter the tank for any reason, such as through the filler cap. So if you put a 964 turbo or 993 filter on a 930 engine, it will (theoretically) intercept all significant dirt that got into the tank, not just dirt coming from the turbo. But of course, there are costs and downsides to doing this too, as discussed above.

Rob
Old 10-06-2007, 10:03 AM
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Thanks guys, just as I thought.

I do however have an idea where the dirt comes from. I have noticed that crud can build up around the top of the oil tank due to condensation. This builds up and gets dislodged when you top the oil up (with or without a funnel). Obviously it can come from the turbo and its scavenge pump as well.
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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 10-06-2007, 02:34 PM
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There is a condition called coking that happens to aircraft engine turbochargers that could explain the chunks of carbon. It is cooked oil from shutdown that has migrated to the tank???
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Old 10-06-2007, 04:51 PM
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