Comment by Texasdude74
02-08-2014, 10:07 PM
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Comment by Texasdude74
He stated in another thread:
Can we get between the flow that the 928 heads get but more than the 944S2 heads?
The spring in the ball-seat is what controls this correct?
For those who aren't familiar with Michael Mount, the best analogy would be he's the Greg Brown of the 944/968 community, best known for his 400+ horsepower 3 liter N/A strokers. So, I asked for his thoughts on this 928 oiling issue and restricting oil flow on these engines. He said he's seen about 25 instances of 944 S2 "tensioner snatching." About 23 of which were caused by lack of maintenance to the tensioning system. He mentioned a big cam/spring track car that had tensioner and cam tooth issues after extended track use. The solution was to fabricate an oil jet to target this area for peace of mind, although he wasn't convinced it was necessary. Cost was under $200, to drill and tap the head and fabricate the sprayer and the problem did not resurface. He strongly recommends limiting oil flow to the top end on the 928. Even to the point of running solid lifters and eliminating lifter flow all together. He says his solid lifter engines survive just fine to 8500 rpm on splash oiling alone and doesn't recommend adding a sprayer (he's only installed the one) unless you're going to really buzz the engine for very lengthy periods. Then he thinks heat build up could eventually become an issue requiring targeted oiling.
After talking with Mike and his experiences then reading the above post from James combined with Kibort's record that no one else can duplicate and the history of his car, I think it's likely Porsche limited flow to the heads on that car.
I'm convinced enough to test this on my engine, which will be wet sumped and will absolutely have the oil flow to the lifters restricted.
After talking with Mike and his experiences then reading the above post from James combined with Kibort's record that no one else can duplicate and the history of his car, I think it's likely Porsche limited flow to the heads on that car.
I'm convinced enough to test this on my engine, which will be wet sumped and will absolutely have the oil flow to the lifters restricted.
Can we get between the flow that the 928 heads get but more than the 944S2 heads?
The spring in the ball-seat is what controls this correct?
02-08-2014, 11:05 PM
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I don't see why not. Yes, the flow is controlled by a spring. I can think of no reason you couldn't adjust flow by changing the spring pressure. It might be a little tricky to change with a high degree of consistency. It's a different setup than the orifice that is commonly used in pushrod engines to reduce flow to the top end.
I think this could be a huge development for the platform. Granted this is just a theory, one that I likely won't be able to personally test until next year.
Seems like most 928 track engine failures can be traced back to the oil out of the pan, into the valve covers and into the intake cycle that Greg has identified. Oil returns in the head being overwhelmed, chimney being plugged with oil. Oil flowing freely into the intake and hammering the bearings to death.
This path has the potential to be the simplest and by far cheapest remedy. However, you can't discount Greg's concerns of unintended consequences. I can't blame him for being hesitant to try something like this on one of his customers engines. I surely wouldn't recommend that Carl make a kit out of this and test it on 50 of his customers cars.
The immediate concerns raised in my feeble brain are sufficient oiling to the lifters and camshafts. I'm feeling more comfortable about this after talking a little bit with Mike M. about his 944's surviving in this very situation.
Comfortable enough that I plan on using S2 restricters, an early pickup and pan combined with a pan spacer and vacuum pump. I might even commit the mortal sin of emergency venting to the header collector!
I think this could be a huge development for the platform. Granted this is just a theory, one that I likely won't be able to personally test until next year.
Seems like most 928 track engine failures can be traced back to the oil out of the pan, into the valve covers and into the intake cycle that Greg has identified. Oil returns in the head being overwhelmed, chimney being plugged with oil. Oil flowing freely into the intake and hammering the bearings to death.
This path has the potential to be the simplest and by far cheapest remedy. However, you can't discount Greg's concerns of unintended consequences. I can't blame him for being hesitant to try something like this on one of his customers engines. I surely wouldn't recommend that Carl make a kit out of this and test it on 50 of his customers cars.
The immediate concerns raised in my feeble brain are sufficient oiling to the lifters and camshafts. I'm feeling more comfortable about this after talking a little bit with Mike M. about his 944's surviving in this very situation.
Comfortable enough that I plan on using S2 restricters, an early pickup and pan combined with a pan spacer and vacuum pump. I might even commit the mortal sin of emergency venting to the header collector!
02-08-2014, 11:52 PM
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J Wise found these for me posted on the Porsche recommended racing modification thread...
Attached Images
File Type: pdf 928Club94Letter.pdf (181.4 KB, 24 views)
File Type: pdf 928CupSpecs.pdf (107.8 KB, 17 views)
Attached Images
File Type: pdf 928Club94Letter.pdf (181.4 KB, 24 views)
File Type: pdf 928CupSpecs.pdf (107.8 KB, 17 views)
02-09-2014, 12:26 PM
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Thanks for the info James, that's very interesting stuff. I think that removes any doubt about whether or not Porsche was aware of what the problem was and if such a mod was ever attempted. It seems like at least a few 928's must have been running around with this setup.
Why is this information coming to light so late in the game? These cars have been out of production for nearly 20 years! Think of the countless barrels of oil ingested by these cars. Billions of knock events, all the pictures of catastrophic failures: torn up bearings, broken rods, junk blocks. To the more minor issues: intake manifolds with small ponds of oil in them, pistons with their own hot tubs of oil on their crowns, and legions of blown head gaskets. Through out these decades of destruction, there's a $200 factory recommended modification complete with part numbers to address this exact problem? A 944 guru is given a synopsis of the problem over the phone and instantly comes up with a solution? A solution it turns out that Porsche themselves thought of and recommended many years ago and no one thought to listen to?
Why is this information coming to light so late in the game? These cars have been out of production for nearly 20 years! Think of the countless barrels of oil ingested by these cars. Billions of knock events, all the pictures of catastrophic failures: torn up bearings, broken rods, junk blocks. To the more minor issues: intake manifolds with small ponds of oil in them, pistons with their own hot tubs of oil on their crowns, and legions of blown head gaskets. Through out these decades of destruction, there's a $200 factory recommended modification complete with part numbers to address this exact problem? A 944 guru is given a synopsis of the problem over the phone and instantly comes up with a solution? A solution it turns out that Porsche themselves thought of and recommended many years ago and no one thought to listen to?
02-09-2014, 01:00 PM
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The head oil flow mod has been around for a while. Obviously since that document but also since the forums were created and actually back to 2000-2001 when there was just "the list". When people emailed people back and forth on "email threads"
People like Waltk and John and other gentleman (some now truly "gone") would talk about long drives.
But not much "racing". At least not the kind we see full color photos of on here. Greg Brown was doing his gig, but without the hassle of us badgering him with emails and texts and forum posts. So he was not even there to suggest it was a bad idea in his opinion.
But it was still referred to as a bad idea - I do not know who was saying it at that time. That is 13 years ago now.
If you spray oil at just the chain tensioner - that may fix it. I have an engine of used parts going together and I could try that if I were to find out where to drill the hole and fit the tube to spray the oil.
Other concerns are not tensioner based. They are that the lifters and cams get too-little oil in low rpm settings - like automatics - and people sitting in traffic.
People like Waltk and John and other gentleman (some now truly "gone") would talk about long drives.
But not much "racing". At least not the kind we see full color photos of on here. Greg Brown was doing his gig, but without the hassle of us badgering him with emails and texts and forum posts. So he was not even there to suggest it was a bad idea in his opinion.
But it was still referred to as a bad idea - I do not know who was saying it at that time. That is 13 years ago now.
If you spray oil at just the chain tensioner - that may fix it. I have an engine of used parts going together and I could try that if I were to find out where to drill the hole and fit the tube to spray the oil.
Other concerns are not tensioner based. They are that the lifters and cams get too-little oil in low rpm settings - like automatics - and people sitting in traffic.
Thanks for the info James, that's very interesting stuff. I think that removes any doubt about whether or not Porsche was aware of what the problem was and if such a mod was ever attempted. It seems like at least a few 928's must have been running around with this setup.
Why is this information coming to light so late in the game? These cars have been out of production for nearly 20 years! Think of the countless barrels of oil ingested by these cars. Billions of knock events, all the pictures of catastrophic failures: torn up bearings, broken rods, junk blocks. To the more minor issues: intake manifolds with small ponds of oil in them, pistons with their own hot tubs of oil on their crowns, and legions of blown head gaskets. Through out these decades of destruction, there's a $200 factory recommended modification complete with part numbers to address this exact problem? A 944 guru is given a synopsis of the problem over the phone and instantly comes up with a solution? A solution it turns out that Porsche themselves thought of and recommended many years ago and no one thought to listen to?
Why is this information coming to light so late in the game? These cars have been out of production for nearly 20 years! Think of the countless barrels of oil ingested by these cars. Billions of knock events, all the pictures of catastrophic failures: torn up bearings, broken rods, junk blocks. To the more minor issues: intake manifolds with small ponds of oil in them, pistons with their own hot tubs of oil on their crowns, and legions of blown head gaskets. Through out these decades of destruction, there's a $200 factory recommended modification complete with part numbers to address this exact problem? A 944 guru is given a synopsis of the problem over the phone and instantly comes up with a solution? A solution it turns out that Porsche themselves thought of and recommended many years ago and no one thought to listen to?
02-09-2014, 01:34 PM
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The head oil flow mod has been around for a while. Obviously since that document but also since the forums were created and actually back to 2000-2001 when there was just "the list". When people emailed people back and forth on "email threads"
People like Waltk and John and other gentleman (some now truly "gone") would talk about long drives.
But not much "racing". At least not the kind we see full color photos of on here. Greg Brown was doing his gig, but without the hassle of us badgering him with emails and texts and forum posts. So he was not even there to suggest it was a bad idea in his opinion.
But it was still referred to as a bad idea - I do not know who was saying it at that time. That is 13 years ago now.
If you spray oil at just the chain tensioner - that may fix it. I have an engine of used parts going together and I could try that if I were to find out where to drill the hole and fit the tube to spray the oil.
Other concerns are not tensioner based. They are that the lifters and cams get too-little oil in low rpm settings - like automatics - and people sitting in traffic.
People like Waltk and John and other gentleman (some now truly "gone") would talk about long drives.
But not much "racing". At least not the kind we see full color photos of on here. Greg Brown was doing his gig, but without the hassle of us badgering him with emails and texts and forum posts. So he was not even there to suggest it was a bad idea in his opinion.
But it was still referred to as a bad idea - I do not know who was saying it at that time. That is 13 years ago now.
If you spray oil at just the chain tensioner - that may fix it. I have an engine of used parts going together and I could try that if I were to find out where to drill the hole and fit the tube to spray the oil.
Other concerns are not tensioner based. They are that the lifters and cams get too-little oil in low rpm settings - like automatics - and people sitting in traffic.
I'm concerned with cam wear as well. Are the 944 cams made out of a different material than the 928? Do they have a higher idle speed? Lower spring pressure or anything else that could account for their ability to survive over the 928 valve train?
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02-09-2014, 01:59 PM
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The 944-2 used a 3.889 final drive but 5th was a .829 overdrive the end result was 3.22 ratio. Or about 22 mph per 1,000 rpm. Also red line is 6,800 rpm.
The engine spends far less time at low RPM far fewer are automatics and getting reasonable performance you have to spin it
all good for oiling but bad for packing the heads. Porsche also increased the oil pan size on the 944 at least three times for SOME reason
The engine spends far less time at low RPM far fewer are automatics and getting reasonable performance you have to spin it
all good for oiling but bad for packing the heads. Porsche also increased the oil pan size on the 944 at least three times for SOME reason
02-09-2014, 08:11 PM
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Not having checked what has been said in another thread I'll just say 4 valve 944's are different than 928. They have actual 3 bar (IIRR) pressure valve instead of 928 ball and spring setup. Using it in 928 heads has been discussed here many many years ago.
02-10-2014, 12:42 PM
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I'm sure something like this could be made to work, if you were so determined. Quick story on unintended consequences and complicated solutions: We built a new house. I hate modern low flow, sissy setups in new homes, I like to take a real shower. So we used commercial sized water lines with no flow restrictors. We are on a well, with the pressure raised 50%. Awesome showers! One day the three year old turns on the water to the bathtub in master bath and wanders off. Drain was open, tub overflowed anyway. Water was going in faster than it was draining out. NEVER thought of that. When we found the wet floor we could have used a bilge pump to remove the excess water, put together a bucket brigade, used a wet vac or an infinite number of ever more complicated methods. Much simpler to shut off the water.
02-10-2014, 12:55 PM
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The 944-2 used a 3.889 final drive but 5th was a .829 overdrive the end result was 3.22 ratio. Or about 22 mph per 1,000 rpm. Also red line is 6,800 rpm.
The engine spends far less time at low RPM far fewer are automatics and getting reasonable performance you have to spin it all good for oiling but bad for packing the heads. Porsche also increased the oil pan size on the 944 at least three times for SOME reason
The engine spends far less time at low RPM far fewer are automatics and getting reasonable performance you have to spin it
all good for oiling but bad for packing the heads. Porsche also increased the oil pan size on the 944 at least three times for SOME reason
02-10-2014, 01:12 PM
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I haven't been able to find any threads on it, must have been many years ago. 45 psi to the heads sounds like plenty to me. These engines have robust oil pumps, massive flow at truly overkill pressures. No one will ever need to upgrade the oil pump. In the Ford modular GT500 world, the oil pump is the first recommended upgrade. Even before headers or exhaust. I have always been told by my engine builder (mainly BBC) that 10 psi for every 1k rpms is more than sufficient. Yet my S4 is nearing 80 psi by 3500 rpms, with 50 weight oil. That's more than twice what the engine needs and is a very large parasitic loss. I've heard of these engines exceeding 100 psi, you don't see that in other engines.
02-10-2014, 07:18 PM
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928 blocks have pressure relief valve which should release extra pressure back to oil pump intake side when it goes over 8.5 bar. Spring setup isn't very accurate and thus actual release pressure can be little less.
03-01-2014, 01:56 PM
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Texas, did you see the pic I posted in my other thread with the pressure valve from the head?