951 rebuild
02-12-2002, 01:39 PM
#32
Hello Erick, et all,
I am a 928 owner, and have had close contact with many people like Devek, who has quite a bit of info on the situation, and other who have actually had thier engines grenade on the track. It amazing that the most destructive things that happen to an engine can usually happen with a wimper. Usually its "There was a stumble, and then white smoke, and nothing,"
My 89 928 is very similar to the GTs of 89-91 (the most that have blown, as they are high rpm cars), and when the engine shuts off EVERY LIGHT goes on in the dash. Very scary.
Anyway, to speak to this subject, I only have 2nd hand info, but some info that must be said noe-the-less. Devek has quite a bit to say about this, but so does another shop, called 928intl
<a href="http://www.928intl.com." target="_blank">www.928intl.com.</a> They have tested the cranks a different way. They, years ago, installed a special drysump oiling system, and ran the car in races. This would have cured the high-side load oil starvation problems. They still blew up engines. So I guess this just proves only part of Devek's point. There IS a problem with the oil startvation problem, but only when you have high Gs, or somehow take flight at a race at high rpm, or take too much oil out of the system as a lister named Ed Ruiz seems to have done.
The ROOT of the problem is still the path that the oil takes. The 32V 928s have this problem even more because out power goes right to 6400rpms. Usually a driver, when in the heat of accelleration, will shift at 6k. Well, that shift is started at 6k, and the engine, in the mean time, has spun to about 6300. This is starting to be rarified air with the oiling at the journal. One issue that the 944s (and 16V 928s) do not have so much is the oil drain back problem, where
the 32V head KEEPS the oil in the head too much, thereby leaving not enough in the pan for pickup. (We use 944 drain back valves for that I think) This is again, oil starvation. So, a good test was when a gentleman took one of thsoe desolate highways up to Alaska, and did it at about 6000rpm in fifth gear (157 range for me). He blew up his engine in a few hours - not because he was G-loading the car - but because his crank was not oiling correctly AND the oil aeration had uncovered the pickup. An Accusump will only give you about 7-10seconds of oil when the pressure drops - fine in a corner, but not when you are running at high speeds on the autobahn. Then its back to basics. If you were to totally make the car a dry sump - for high rpm sustained loads, you STILL need the crank drilled.
ON that note, I am unsure if Deveks's drilling, 928intl's drilling, and Huntley's drilling are at all different.
Brendan
89S4 5spd.
I am a 928 owner, and have had close contact with many people like Devek, who has quite a bit of info on the situation, and other who have actually had thier engines grenade on the track. It amazing that the most destructive things that happen to an engine can usually happen with a wimper. Usually its "There was a stumble, and then white smoke, and nothing,"
My 89 928 is very similar to the GTs of 89-91 (the most that have blown, as they are high rpm cars), and when the engine shuts off EVERY LIGHT goes on in the dash. Very scary.
Anyway, to speak to this subject, I only have 2nd hand info, but some info that must be said noe-the-less. Devek has quite a bit to say about this, but so does another shop, called 928intl
<a href="http://www.928intl.com." target="_blank">www.928intl.com.</a> They have tested the cranks a different way. They, years ago, installed a special drysump oiling system, and ran the car in races. This would have cured the high-side load oil starvation problems. They still blew up engines. So I guess this just proves only part of Devek's point. There IS a problem with the oil startvation problem, but only when you have high Gs, or somehow take flight at a race at high rpm, or take too much oil out of the system as a lister named Ed Ruiz seems to have done.
The ROOT of the problem is still the path that the oil takes. The 32V 928s have this problem even more because out power goes right to 6400rpms. Usually a driver, when in the heat of accelleration, will shift at 6k. Well, that shift is started at 6k, and the engine, in the mean time, has spun to about 6300. This is starting to be rarified air with the oiling at the journal. One issue that the 944s (and 16V 928s) do not have so much is the oil drain back problem, where
the 32V head KEEPS the oil in the head too much, thereby leaving not enough in the pan for pickup. (We use 944 drain back valves for that I think) This is again, oil starvation. So, a good test was when a gentleman took one of thsoe desolate highways up to Alaska, and did it at about 6000rpm in fifth gear (157 range for me). He blew up his engine in a few hours - not because he was G-loading the car - but because his crank was not oiling correctly AND the oil aeration had uncovered the pickup. An Accusump will only give you about 7-10seconds of oil when the pressure drops - fine in a corner, but not when you are running at high speeds on the autobahn. Then its back to basics. If you were to totally make the car a dry sump - for high rpm sustained loads, you STILL need the crank drilled.
ON that note, I am unsure if Deveks's drilling, 928intl's drilling, and Huntley's drilling are at all different.
Brendan
89S4 5spd.
02-12-2002, 03:02 PM
#33
Race Car
I don't agree with this part:
[quote]It will happen more frequently and sooner on a S4 then on an early engine
with the same cornering capability due to the fact that there are less
places for the oil to stay in the head and the paths in the head are
smaller. So more oil stays in the pan.<hr></blockquote>
Unless he's describing the early engine that will leave more oil in the pan, not the S4.
[quote]It will happen more frequently and sooner on a S4 then on an early engine
with the same cornering capability due to the fact that there are less
places for the oil to stay in the head and the paths in the head are
smaller. So more oil stays in the pan.<hr></blockquote>
Unless he's describing the early engine that will leave more oil in the pan, not the S4.
02-12-2002, 08:15 PM
#34
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My butt feels like an airline seat has been permantly attached to it.
I see the cross drill issue has come up and the 90° issue. HMMM, I have a question about the knife edged/lightened crank. If you lessen the rotating mass on the crank, should the flywheel be lightened too? I've heard of several shredding themselves, just wondering if the knife edged crank will have any problem supporting the original flywheel load. I know that it takes nothing away from the strength just wondering...I have a chance to pick up the crank before the rebuild but can't pull off both right now,,,my "boost control" has kicked at home..LOL! Anybody running a Garrity lightened/knife edged crank? I know he does great work.
I see the cross drill issue has come up and the 90° issue. HMMM, I have a question about the knife edged/lightened crank. If you lessen the rotating mass on the crank, should the flywheel be lightened too? I've heard of several shredding themselves, just wondering if the knife edged crank will have any problem supporting the original flywheel load. I know that it takes nothing away from the strength just wondering...I have a chance to pick up the crank before the rebuild but can't pull off both right now,,,my "boost control" has kicked at home..LOL! Anybody running a Garrity lightened/knife edged crank? I know he does great work.
02-13-2002, 12:10 AM
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As far as I know, we are the only ones that Perp drill. I am sure others will follow as time goes on but thier prices will go up because it is much mor difficult than the x-drill. As one liter mentioned even dry sump motors have the failure of the rod bearings which completly validates our position on this. It has nothing to do with the pickup. There is never a pickup issue with a dry sump motor. I stand behind our flawless record. I'm not trying to be snooty but this has saved many many 944 AND 928 motors (yes we build those too) 
02-13-2002, 12:29 PM
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I read all the 944 Rebuild posting. It's a good thread and there's a lot there to consider. I'm going to be really critical though and I hope my being critical this way doesn't put anyone's nose out of joint. If Huntley or someone can address these criticisms I'd genuinely appreciate it, as I'm rebuilding my 931 engine presently. Here goes..,
It's an 'interesting idea' that more holes placed by Huntley equals no rod failure. But I'm not sure they have it nailed down:
a. Why this engine, or the Chevy big block, should be special, has still eluded everyone. They point to RPM's being a problem...so some 'band' or 'range' of RPM leads to engine failure (those 'bad' RPM's!). Yet, if centripetal force affects any oiled crank if that same crank does not have additional 'holes', then there should be some 'theoretical' RPM at which any bearings on any car will fail - we just have to get the RPM's to that 'bad band'. But this doesn't happen. We see Japanese cranks without additional holes going through cycles up to 10000 RPMs (Acura NSX), Formula 2000 cars reaching 6000 RPM regularly without a problem, my Porsche 924 running at 7000 RPM's regularly, the WRX with a redline of 8000 RPMs...the list goes on and on and on. No one else has had to drill holes in a crank or bearing to this extent. Still, no problem. Why? Oh, maybe it's some 'magic' feature of the 944 crank, that is also shared by the Chevy crank. Bah! Humbug. Further, there are thousands of other manufacturers and still they do not have extra holes in their crank or bearings. Readers have not yet addressed this crucial 'in your face' fact.
Convincing evidence for me would be if someone could show me:
1. A manufacturer making a system with no holes and then...
2. The same manufacturer making a system with these holes and then
3. Showing us how the lifetime of the system created in (2) leads to a longer life system.
I've seen no evidence of that yet.
b. The idea of an additional hole to augment oil flow is good in any situation. It's hard to conceive of an engine part that could not benefit from additional oil leads. So the idea that it 'must' be in this particular spot due to centripital force is interesting, though debatable, and many posters did debate this point, though they were given a good explanation by Danno that I thought was superb. However, I suspect holes lead to decreased structural strength, so on the weight of the evidence I'd hesitate before taking the Wagner portable and a titanium drill bit to my crank.
Convincing evidence would be a computer simulation of the effect, showing cooling happening at the rods in the affected area. That's a no brainer with the right software.
c. I'm not convinced that Huntley's technique has in fact led to the decreased incidence of engine failure in their rebuilt engines. Huntley reports no engine failures on up to 40 944 turbos they've done with this technique. Yet, the technique has only been used by Huntley since 1998, so the fact that there has been no breakdowns of this kind on, at most, a 3 year old engine, is far from surprising. In fact, were there to be a breakdown of any type on a 2 year old rebuilt engine, at the prices they charge, I would expect a successful lawsuit.
Convincing evidence to counter my claim would be to show me two approximately matched 944 Turbos, each with Huntley's total rebuild, but one having the cross drilled holes and the other not. We should see, under identical driving conditions, the non-drilled car fail and the drilled car not fail. I don't see that evidence.
(In fact, it might be that a good engine rebuild by Huntley, sans holes, leads to better oil cooling throughout the system, regardless of the holes.)
And, of course, as my friend R points out...two additional questions as yet unanswered:
1. Why #2? (The problem should be dispersed across all bearings equally, unless the hole placement is different at the #2 portion of the crank)
2. Where to other manufacturers place their holes? (i.e., does their placement differ by 90 degrees from Porsche's placement?)
Thanks R.
Danno: I'm not sure on this, but, if you drill a second hole of the same diameter as the first, wouldn't the resultant length of the force vectors be correspondingly halved, thus dispersing less oil per hole, but the same amount of oil overall? The latter diagram shows the resultant force vectors to be of identical length, and if length represents force (or volume) then they might be halved.
It's an 'interesting idea' that more holes placed by Huntley equals no rod failure. But I'm not sure they have it nailed down:
a. Why this engine, or the Chevy big block, should be special, has still eluded everyone. They point to RPM's being a problem...so some 'band' or 'range' of RPM leads to engine failure (those 'bad' RPM's!). Yet, if centripetal force affects any oiled crank if that same crank does not have additional 'holes', then there should be some 'theoretical' RPM at which any bearings on any car will fail - we just have to get the RPM's to that 'bad band'. But this doesn't happen. We see Japanese cranks without additional holes going through cycles up to 10000 RPMs (Acura NSX), Formula 2000 cars reaching 6000 RPM regularly without a problem, my Porsche 924 running at 7000 RPM's regularly, the WRX with a redline of 8000 RPMs...the list goes on and on and on. No one else has had to drill holes in a crank or bearing to this extent. Still, no problem. Why? Oh, maybe it's some 'magic' feature of the 944 crank, that is also shared by the Chevy crank. Bah! Humbug. Further, there are thousands of other manufacturers and still they do not have extra holes in their crank or bearings. Readers have not yet addressed this crucial 'in your face' fact.
Convincing evidence for me would be if someone could show me:
1. A manufacturer making a system with no holes and then...
2. The same manufacturer making a system with these holes and then
3. Showing us how the lifetime of the system created in (2) leads to a longer life system.
I've seen no evidence of that yet.
b. The idea of an additional hole to augment oil flow is good in any situation. It's hard to conceive of an engine part that could not benefit from additional oil leads. So the idea that it 'must' be in this particular spot due to centripital force is interesting, though debatable, and many posters did debate this point, though they were given a good explanation by Danno that I thought was superb. However, I suspect holes lead to decreased structural strength, so on the weight of the evidence I'd hesitate before taking the Wagner portable and a titanium drill bit to my crank.
Convincing evidence would be a computer simulation of the effect, showing cooling happening at the rods in the affected area. That's a no brainer with the right software.
c. I'm not convinced that Huntley's technique has in fact led to the decreased incidence of engine failure in their rebuilt engines. Huntley reports no engine failures on up to 40 944 turbos they've done with this technique. Yet, the technique has only been used by Huntley since 1998, so the fact that there has been no breakdowns of this kind on, at most, a 3 year old engine, is far from surprising. In fact, were there to be a breakdown of any type on a 2 year old rebuilt engine, at the prices they charge, I would expect a successful lawsuit.
Convincing evidence to counter my claim would be to show me two approximately matched 944 Turbos, each with Huntley's total rebuild, but one having the cross drilled holes and the other not. We should see, under identical driving conditions, the non-drilled car fail and the drilled car not fail. I don't see that evidence.
(In fact, it might be that a good engine rebuild by Huntley, sans holes, leads to better oil cooling throughout the system, regardless of the holes.)
And, of course, as my friend R points out...two additional questions as yet unanswered:
1. Why #2? (The problem should be dispersed across all bearings equally, unless the hole placement is different at the #2 portion of the crank)
2. Where to other manufacturers place their holes? (i.e., does their placement differ by 90 degrees from Porsche's placement?)
Thanks R.
Danno: I'm not sure on this, but, if you drill a second hole of the same diameter as the first, wouldn't the resultant length of the force vectors be correspondingly halved, thus dispersing less oil per hole, but the same amount of oil overall? The latter diagram shows the resultant force vectors to be of identical length, and if length represents force (or volume) then they might be halved.
02-13-2002, 02:08 PM
#38
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Hey BigPorscheGuy39. I Like seeing you around because you are keeping on of my favorite cars on the road, the 924!
Anyway. I think people cross drill each rod journal (it only makes sense). #2 isn't the only bearing that people have seen wear poorly. Often when people open their motors up #3 it pretty bad too.
As for the "proof" that it works, I agree with you. I think Huntley charges $900 to lighten, balance, and cross drill. Even if there is no "proof", it still seems like a good investment for a track car.
Anyway. I think people cross drill each rod journal (it only makes sense). #2 isn't the only bearing that people have seen wear poorly. Often when people open their motors up #3 it pretty bad too.
As for the "proof" that it works, I agree with you. I think Huntley charges $900 to lighten, balance, and cross drill. Even if there is no "proof", it still seems like a good investment for a track car.
02-13-2002, 03:02 PM
#39
Race Director
[quote]We see Japanese cranks without additional holes going through cycles up to 10000 RPMs (Acura NSX), Formula 2000 cars reaching 6000 RPM regularly without a problem, my Porsche 924 running at 7000 RPM's regularly, the WRX with a redline of 8000 RPMs...the list goes on and on and on. No one else has had to drill holes in a crank or bearing to this extent. Still, no problem. Why?<hr></blockquote>I'm assuming these guys got it right the first time and put a single hole in their rod-journals; but on the very outside instead of on the side like our 944s. It's not that it needs a second hole, but where that hole is placed. On all of the motorcycle engines I've taken apart, the oil hole on the rod-journals is always on the very outside. I spin them up to 13,000rpm all the time without any problems.
[quote]Danno: I'm not sure on this, but, if you drill a second hole of the same diameter as the first, wouldn't the resultant length of the force vectors be correspondingly halved, thus dispersing less oil per hole, but the same amount of oil overall?<hr></blockquote>I think so, that's why in my final picture, there very little coming out the side hole. Check out this recent thread on that particular subject:<a href="http://forums.rennlist.com/scripts/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=003359" target="_blank">cross drilling crank</a> for why the second hole doesn't reduce pressure to both. That would only be the if the pump was already at the limit with a single hole. I would surmise that at low-RPM, there's more than enough pressure and flow to supply both holes with identical pressure, ensuring an even layer at the bearings (the limiting factor is the clerance and how much it can flow at any given pressure). However, at high-RPM, there will be very little flow out the side hole anyway, so most of the oil-pressure and extra added by centripedal force will flow out the outermost hole.
[quote]Oh, maybe it's some 'magic' feature of the 944 crank, that is also shared by the Chevy crank.<hr></blockquote>I think there's still some other factor going on here since the hole-placement idea still doesn't explain why the #2 bearing has much, much more severe wear than the others. Here's a summary of my rod-bearings at 196k-miles:
The #2 bearings was by far the worse. #1 was next with a shiny used finish. #3 &4 were still dull-looking with a like-new finish (look away from central reflection).
I like the idea in Erick's post about the #2 getting the first dosage of air as being the cause. It'd be interesting to measure the path lengths from the oil-pump to each of the rod-journals.
[quote]Danno: I'm not sure on this, but, if you drill a second hole of the same diameter as the first, wouldn't the resultant length of the force vectors be correspondingly halved, thus dispersing less oil per hole, but the same amount of oil overall?<hr></blockquote>I think so, that's why in my final picture, there very little coming out the side hole. Check out this recent thread on that particular subject:<a href="http://forums.rennlist.com/scripts/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=003359" target="_blank">cross drilling crank</a> for why the second hole doesn't reduce pressure to both. That would only be the if the pump was already at the limit with a single hole. I would surmise that at low-RPM, there's more than enough pressure and flow to supply both holes with identical pressure, ensuring an even layer at the bearings (the limiting factor is the clerance and how much it can flow at any given pressure). However, at high-RPM, there will be very little flow out the side hole anyway, so most of the oil-pressure and extra added by centripedal force will flow out the outermost hole.
[quote]Oh, maybe it's some 'magic' feature of the 944 crank, that is also shared by the Chevy crank.<hr></blockquote>I think there's still some other factor going on here since the hole-placement idea still doesn't explain why the #2 bearing has much, much more severe wear than the others. Here's a summary of my rod-bearings at 196k-miles:
The #2 bearings was by far the worse. #1 was next with a shiny used finish. #3 &4 were still dull-looking with a like-new finish (look away from central reflection).
I like the idea in Erick's post about the #2 getting the first dosage of air as being the cause. It'd be interesting to measure the path lengths from the oil-pump to each of the rod-journals.
02-13-2002, 06:35 PM
#40
If it was caused by centripedal force, it would be RPM related and would be repeatable... exceeded 6,000+ RPM for xx seconds and rod failure.
See simular BMW problem below;
Update-8/99-E30 M3 Oil Sump Problems
We have seen an increase in BMW E30 M3 motors losing rod bearings in driving school and club racing conditions here on the East coast, plus reports from the West coast and tuning firms and customers overseas.
The newest "spec" tires now coming into increased use, BFG G-Force, Goodyear GS-CS, Hoosiers, etc, along with improved suspension systems, generate cornering forces previously experienced only with racing slicks. In hard braking and cornering, oil surging in the pan can cause oil pickup problems. The BMW Motorsport type oil baffle added to the stock pan that has worked so well for the past 10-12 years may not provide sufficient protection under these new conditions. Modified engines carrying higher RPM through corners add to the problem. At high RPM, oil is pumped to the head faster than it can drain back to the pan, further lowering the oil level around the pick up.
In marginal conditions, two identical M3's may run through a long corner at the same speed. The one in third gear and 7600 RPM may lose his rod bearings. The other, in fourth gear at 5500 may have no trouble at all.
See simular BMW problem below;
Update-8/99-E30 M3 Oil Sump Problems
We have seen an increase in BMW E30 M3 motors losing rod bearings in driving school and club racing conditions here on the East coast, plus reports from the West coast and tuning firms and customers overseas.
The newest "spec" tires now coming into increased use, BFG G-Force, Goodyear GS-CS, Hoosiers, etc, along with improved suspension systems, generate cornering forces previously experienced only with racing slicks. In hard braking and cornering, oil surging in the pan can cause oil pickup problems. The BMW Motorsport type oil baffle added to the stock pan that has worked so well for the past 10-12 years may not provide sufficient protection under these new conditions. Modified engines carrying higher RPM through corners add to the problem. At high RPM, oil is pumped to the head faster than it can drain back to the pan, further lowering the oil level around the pick up.
In marginal conditions, two identical M3's may run through a long corner at the same speed. The one in third gear and 7600 RPM may lose his rod bearings. The other, in fourth gear at 5500 may have no trouble at all.
02-13-2002, 07:13 PM
#42
If #2 rod, as stated above for the 928, is first in line in the oil path, it would receive no oil, overheat, the film barrier fails, then metal to metal. If the process happened quickly and the motor seized/stopped, the other bearing might survive . What was the timescale of your #2 failure? If someone has a block in their livingroom, maybe they could map the lengths of the oil path to the rods.
02-13-2002, 07:38 PM
#43
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Looking at those rod bearings makes my stomach turn. That's poor lubrication engineering to the max. Maybe its due to the excessive rpms (danno probably revs to 6500-7000), or the lack of a baffle on the stock 86 bottom end, or the aireation, but intuitively it looks like the lubrication path itself is substantially different judging from the dramatic difference n wear.
Here's a generic image of an engine block showing oil galleries:
Here's a generic image of an engine block showing oil galleries:
02-13-2002, 08:55 PM
#44
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Here's a good site illustrating types of plain bearing wear...
<a href="http://www.thirskauto.net/BearingPics.html" target="_blank">http://www.thirskauto.net/BearingPics.html</a>
here's a pic of the oil starvation bearing that appears similar to Danno's bearing:
And hear's a faitgue (detonation included) bearing:
<a href="http://www.thirskauto.net/BearingPics.html" target="_blank">http://www.thirskauto.net/BearingPics.html</a>
here's a pic of the oil starvation bearing that appears similar to Danno's bearing:
And hear's a faitgue (detonation included) bearing:
02-14-2002, 12:21 AM
#45
Race Director
[quote]What was the timescale of your #2 failure? <hr></blockquote>The bearing actually didn't fail, the car was still running fine when I took it apart. I had a really bad oil-leak from the front of the engine, so I replaced the crank & balance-shaft seals. I figured I might as well do the rod-bearings and oil-pan gasket. I was going to buy one of those "update" oil-pan baffles, but mine looked exactly the same, so I'm not sure what's the difference is besides part numbers. The crank itself was in good condition:
I borrowed a guy from one of my friend's machine shop and had him measure the rod-journals. They were all well within specs and I threw in the replacement bearings. The Plastigage clearance test was in the middle of the allowable range. So I threw everything back together.
Due to the good condition of the crank vs. the bearing, I think it was a very short-term catastrophic event that caused the bearing wear you see. If it was a chronic problem like oil-starvation at high-RPM, I think the crank would've been toast since I race on the tracks every three weeks or so. It might have been the few times my oil-pressure light went on as I was coming to a stoplight (due to my low-oil level from leaks). This was at low-RPM and no load, so I think that's why the bearing didn't spin or cause other problems. If it had happened at high-RPM at maximum cornering on the track, I think the crank would definitely be gone.
Anyway, no definite conclusions yet as to why #2 is more susceptible than the others.
I borrowed a guy from one of my friend's machine shop and had him measure the rod-journals. They were all well within specs and I threw in the replacement bearings. The Plastigage clearance test was in the middle of the allowable range. So I threw everything back together.
Due to the good condition of the crank vs. the bearing, I think it was a very short-term catastrophic event that caused the bearing wear you see. If it was a chronic problem like oil-starvation at high-RPM, I think the crank would've been toast since I race on the tracks every three weeks or so. It might have been the few times my oil-pressure light went on as I was coming to a stoplight (due to my low-oil level from leaks). This was at low-RPM and no load, so I think that's why the bearing didn't spin or cause other problems. If it had happened at high-RPM at maximum cornering on the track, I think the crank would definitely be gone.
Anyway, no definite conclusions yet as to why #2 is more susceptible than the others.