Drilled Crank Thoughts...
09-28-2007, 07:39 PM
#76
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I also believe that a 928 with stock oil passages will soon fail at a steady 7000 rpms even on a dyno with virgin oil fed to the pump
It also mentions testing a motor up to 8,200 rpm to check the hydraulic lifters but it was a 6 cylinder motor and again no clue about the crank used.
It would be very interesting to get more details of such testing.
I have to believe that they did long tests at max revs but there is no clear statement of this.
It also says that they planned a race version of the motor but no more details in this book if this version ever saw the light of day.
Marton
09-29-2007, 12:48 PM
#77
Race Car
09-29-2007, 04:02 PM
#78
Race Car
https://rennlist.com/forums/928-forum/255033-help-me-thank-corky-and-bell-intercoolers-for-their-support.html
He mentions it is his laundry list in post 9. Doesn't say where/when it took place. I think this is the laundry list he had up on his website previously. Now the engine puts out even more power.
He mentions it is his laundry list in post 9. Doesn't say where/when it took place. I think this is the laundry list he had up on his website previously. Now the engine puts out even more power.
09-29-2007, 04:15 PM
#79
Rennlist Member
Aren't the 16 valve motors (like Carl's) exempt from the 2/6 issue? I thought that part of the oiling starvation problem was oil staying trapped in the big 32v heads. I don't think I've every heard of 16v motor blowing the 2/6. Isn't this one of the reason to build the 5L Euro/hybrid motor so you can take advantage of using the smaller heads?
09-29-2007, 04:45 PM
#80
Road Warrior
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good point adam... when greg did his windage trays for our strokers he paid special attention to insuring the return drains stayed clear of the crank. he also lowered the pan a bit to keep the larger throws out of the oil. seemed to work on the track pretty well.
09-29-2007, 08:46 PM
#81
Former Sponsor
No motorcycle crank with the journal size or oiling of a 928 is going to live over 6-7000 rpms. I also believe that a 928 with stock oil passages will soon fail at a steady 7000 rpms even on a dyno with virgin oil fed to the pump, the rod bearings will starve while the pressure gage looks good.
If the journal is a large enough diameter and the rpms high enough and the oil has to reach the center of the crank before it can go up to the rods, the centrifical force will be greater than the supply pressure at a certain point. In a 928's cross drilled crank the force of the oil in that channel will cancel out the supply pressure somewhere within high rpms ranges, I would guess by 7000 rpms. At that point the oil column going to the rods will cavitate and no more oil will reach them until rpms drop. Aeration of the oil within the crank's oil passage's is probably happening too before the critical pressure cancellation point, and that can be with a perfect supply of nice oil.
If the journal is a large enough diameter and the rpms high enough and the oil has to reach the center of the crank before it can go up to the rods, the centrifical force will be greater than the supply pressure at a certain point. In a 928's cross drilled crank the force of the oil in that channel will cancel out the supply pressure somewhere within high rpms ranges, I would guess by 7000 rpms. At that point the oil column going to the rods will cavitate and no more oil will reach them until rpms drop. Aeration of the oil within the crank's oil passage's is probably happening too before the critical pressure cancellation point, and that can be with a perfect supply of nice oil.
We kid the heck out of Kibort about Amsoil, but the fact that he has higher oil pressure with Amsoil than other oils, means that the oil will travel farther towards the center of the crank before the centrifical force stops the oil from moving. The differences between oils and what they do can be significant. Amsoil might disipate heat quicker, which results in cooler oil and thus more oil pressure, or it might be underated slightly in viscosity, which increases oil pressure.
I learned many years ago not to take anything for granted. I was on a Nascar team and we were running at Ontario (California) (few years back). We were fighting a severe case of really high oil temperature all day (over 250 degrees). Nothing we did seemed to help. We were running a 20-50 Union Oil product. Some old guy in coveralls came by our door (Junior Johnson) and stopped and took a look around. We had no clue who he was, so we kind of all chuckled at the "hick" at our door. The first thing out of his mouth was "You guys having oil temperature problems today?" He pointed at our stack of cases of oil and said "You guys running that stuff?"
No one had talked to anybody outside our garage about our oil temperature problems, so this caught our attention.
He went on to say "You go get you some of that straight 50 weight Union Oil stuff over there and you will cure your problems. That multi-viscosity crap doesn't let go of the heat fast enough."
We laughed and thanked the hick as he moved on. As soon as he was out of sight, someone immediately was sent running over to the Union Oil trailer to get some straight 50 weight. We changed the oil and guess what......lost 50 degrees of stinking oil temperature!!!
The moral of the story is:
It's possible that Kibort might turn out to be a hick in coveralls, in the end.
09-30-2007, 08:07 AM
#82
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Aren't the 16 valve motors (like Carl's) exempt from the 2/6 issue? I thought that part of the oiling starvation problem was oil staying trapped in the big 32v heads. I don't think I've every heard of 16v motor blowing the 2/6. Isn't this one of the reason to build the 5L Euro/hybrid motor so you can take advantage of using the smaller heads?
Not sure about the premise, but the my motors failures (2/6 rod bearing) were 16v heads on 5L shortblocks. David Lloyd went through at least a couple the same way. John Veninger didn't but replaced rod bearings with significant wear. Some failures happened with accusumps and some with drilled cranks.
Dave Cooley had the same problem with a 4.7L motor (no 5L short block).
09-30-2007, 08:09 AM
#83
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Here's my 2 cents, for what it is worth.
Any crankshaft with damage that caused distortion needs to be thrown away. Repaired, welded, chromed cranks usually break into two pieces fairly quickly. This is "used car lot" repair proceedures. Most cranks that are ground undersize have flaws in the radius and they will also break. A very good crank grinder will radius their stones and not get this "chatter" in the radius. "Good" crank grinders are expensive, as it takes longer to do things this way. Most people don't know the difference, so "good" crank grinders are very rare! If you have a crank ground and it has "chatter" marks on the radius, throw it away and smile.
Your crank was not drilled anywhere near correctly. One of the problems with the 928 is that #2 and #6get their oil last....not first! To improve the oiling, you need to drill the #3 main bearing to supply oil to these rods. The main bearings need to be modified to supply oil to the rods throughout the rotation of the crankshaft.
What rod bearings were used? I'm betting a set of "aftermarket" Glyco bearings. Nice price. Not enough oil clearance.
Jay Steele at Taylor Engine has a guy that knows how to do this. I had him do the very first one to my specifications and he's done many of them since. Jay is a "world class" machinist. He's also very busy. The two go hand in hand, in my opinion.
Any crankshaft with damage that caused distortion needs to be thrown away. Repaired, welded, chromed cranks usually break into two pieces fairly quickly. This is "used car lot" repair proceedures. Most cranks that are ground undersize have flaws in the radius and they will also break. A very good crank grinder will radius their stones and not get this "chatter" in the radius. "Good" crank grinders are expensive, as it takes longer to do things this way. Most people don't know the difference, so "good" crank grinders are very rare! If you have a crank ground and it has "chatter" marks on the radius, throw it away and smile.
Your crank was not drilled anywhere near correctly. One of the problems with the 928 is that #2 and #6get their oil last....not first! To improve the oiling, you need to drill the #3 main bearing to supply oil to these rods. The main bearings need to be modified to supply oil to the rods throughout the rotation of the crankshaft.
What rod bearings were used? I'm betting a set of "aftermarket" Glyco bearings. Nice price. Not enough oil clearance.
Jay Steele at Taylor Engine has a guy that knows how to do this. I had him do the very first one to my specifications and he's done many of them since. Jay is a "world class" machinist. He's also very busy. The two go hand in hand, in my opinion.
I can assure you I didn't get a deal on the crank drilling even if it wasn't done correctly.
Ok, it will go to the scrap yard on the next run, didn't think there would be much interest anyways lmao
09-30-2007, 10:41 PM
#85
Former Sponsor
Stan:
There was a post sometime back about someone who changed their original rod bearings, even though they looked pretty good, and replaced them with an aftermarket set....and promptly lost a rod bearing.
Get the bearing clearance under .002" and you are going to have trouble. I've measured clearances as low as .001" with the Glyco bearings.
There was a post sometime back about someone who changed their original rod bearings, even though they looked pretty good, and replaced them with an aftermarket set....and promptly lost a rod bearing.
Get the bearing clearance under .002" and you are going to have trouble. I've measured clearances as low as .001" with the Glyco bearings.
09-30-2007, 10:51 PM
#86
Former Sponsor
Kevin:
Indeed there are known multiple problems with the 928s loosing rod bearings, which I have discussed many times. There are at least 4 differrent factors involved in this problem, with-in the 928 engine. Solve one, think you have it fixed, and then another jumps up to bite you. As I've said before, Mark Anderson's race engine hurts stock rod bearings, even though it is dry sumped.
Your thoughts are interesting. How hot do you think the oil gets when it is in use between the rod and the crank? Is there any data on this? It seems like it would have to fairly significant to have the air bubbles expand enough to be a factor. If it was this significant, the exiting oil would have to be very, very hot.
Indeed there are known multiple problems with the 928s loosing rod bearings, which I have discussed many times. There are at least 4 differrent factors involved in this problem, with-in the 928 engine. Solve one, think you have it fixed, and then another jumps up to bite you. As I've said before, Mark Anderson's race engine hurts stock rod bearings, even though it is dry sumped.
Your thoughts are interesting. How hot do you think the oil gets when it is in use between the rod and the crank? Is there any data on this? It seems like it would have to fairly significant to have the air bubbles expand enough to be a factor. If it was this significant, the exiting oil would have to be very, very hot.
10-01-2007, 09:53 PM
#87
Former Sponsor
Since the aftermarket guys and the hot rodders don't have the budget of the military or the oem guys, we sometimes have to do some educated guessing, instead of expensive testing.
We do know this:
Drilling the crankshaft, so that the oil doesn't have to try to fight its' way to the center of the main bearing, helps the rods get oil at higher rpms. This might be a lack of pressure to get the oil there, it might be a lack of viscosity that reduces the pressure, so the oil can't get there, or it might be air bubbles expanding in the oil, so the oil can't get there. Not sure it matters, as long as drilling the crank, like the majority of the race cranks (in this country) are done, seems to cure this portion of the problem. There are at least 3 further problems that are not solved by this fix, and it is very possible/likely to loose a rod bearing with a drilled crank.
I'm sure that any improvement in controlling the windage problem in the 928 engine will help greatly, but it will not remove all of the known factors that cause bearing failures.
We do know this:
Drilling the crankshaft, so that the oil doesn't have to try to fight its' way to the center of the main bearing, helps the rods get oil at higher rpms. This might be a lack of pressure to get the oil there, it might be a lack of viscosity that reduces the pressure, so the oil can't get there, or it might be air bubbles expanding in the oil, so the oil can't get there. Not sure it matters, as long as drilling the crank, like the majority of the race cranks (in this country) are done, seems to cure this portion of the problem. There are at least 3 further problems that are not solved by this fix, and it is very possible/likely to loose a rod bearing with a drilled crank.
I'm sure that any improvement in controlling the windage problem in the 928 engine will help greatly, but it will not remove all of the known factors that cause bearing failures.
10-02-2007, 01:10 AM
#88
Former Sponsor
Kevin:
Why the frustration?
We are just passing thoughts back and forth here.
I understand your points. I'm not debating them. An endless supply of filtered, bubble free oil will do wonders in an engine.
That being said, you should try and stop and understand what I'm saying.
None of the engines you mention have anywhere near the main journal diameter of the 928, nor do they oil like a 928. There is a physical limit, due to centrifugal force, that you can force oil to the very center of a spinning object. Once that limit is reached, there are only three ways to solve the problem. You either need to increase the pressure pushing against the centrifugal force, slow the revolutions so that the affects of the force is decreased, or change the path so that the fluid can get to its' destination through a different path.
Why the frustration?
We are just passing thoughts back and forth here.
I understand your points. I'm not debating them. An endless supply of filtered, bubble free oil will do wonders in an engine.
That being said, you should try and stop and understand what I'm saying.
None of the engines you mention have anywhere near the main journal diameter of the 928, nor do they oil like a 928. There is a physical limit, due to centrifugal force, that you can force oil to the very center of a spinning object. Once that limit is reached, there are only three ways to solve the problem. You either need to increase the pressure pushing against the centrifugal force, slow the revolutions so that the affects of the force is decreased, or change the path so that the fluid can get to its' destination through a different path.
10-02-2007, 08:40 AM
#89
Pro
Just thinking out loud here
10-02-2007, 09:03 AM
#90
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How about using an electrical centrifuge to separate oil and gas before it enters the pump?