Engine ka-boom follow-up
08-09-2005, 06:06 PM
#1
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Engine ka-boom follow-up
As you may recall, my engine went ka-boom a short while ago. I dropped it off Saturday at the shop. I can't believe I didn't see the hole when I first looked. It's as big as my fist.
It's a cell phone camera, but ugly is ugly.
It appears the rod bolt for #5 died and took my engine with it. We are puzzled why it happened as I've never over-reved the car in the 2 years I've had it. But that doesn't change the fact I need a new engine. Sigh. Isn't this track stuff fun?
It's a cell phone camera, but ugly is ugly.
It appears the rod bolt for #5 died and took my engine with it. We are puzzled why it happened as I've never over-reved the car in the 2 years I've had it. But that doesn't change the fact I need a new engine. Sigh. Isn't this track stuff fun?
08-09-2005, 06:28 PM
#2
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Damn, Tom. That's a painful picture to look at. So, what's exactly going to be involved with your "new" engine? Sorry to hear & see the news about your engine.
08-09-2005, 06:38 PM
#4
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Ka-boom is right. Yikes. No missed shifts or over heating?
I guess the tear down will determine if it was a rod bearing or bolt that failed.
Either way....what a bummer.
I guess the tear down will determine if it was a rod bearing or bolt that failed.
Either way....what a bummer.
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08-09-2005, 08:41 PM
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While I've never missed a shift and over-reved it, the car has about 75k miles and has been a track appliance for a while. I thought that some of that epxy weld stuff might do the trick for the whole but, unfortunately, to get it to the right spots on the inside you still have to take the engine apart.
I plan to do as little "enhancement" as possible on the rebuild as I want to stay in a stock class for racing.
I plan to do as little "enhancement" as possible on the rebuild as I want to stay in a stock class for racing.
08-09-2005, 09:55 PM
#11
RL Technical Advisor
Originally Posted by Tom W
As you may recall, my engine went ka-boom a short while ago. I dropped it off Saturday at the shop. I can't believe I didn't see the hole when I first looked. It's as big as my fist.
It appears the rod bolt for #5 died and took my engine with it. We are puzzled why it happened as I've never over-reved the car in the 2 years I've had it. But that doesn't change the fact I need a new engine. Sigh. Isn't this track stuff fun?
It appears the rod bolt for #5 died and took my engine with it. We are puzzled why it happened as I've never over-reved the car in the 2 years I've had it. But that doesn't change the fact I need a new engine. Sigh. Isn't this track stuff fun?
Thats the classic lubrication failure on 911 engines; the #2 or # 5 rod bearing.
These crankshafts are end-oiled and the center two rod journals are the last places to receive oil. When rod bearings fail (there are many reasons involved), those two are the ones that usually fail.
If the engine is to see mostly track/race use, there are several things that can be done to improve durability/reliability under such conditions. Different rods, GT-3R oil pumps and cross-drilled crankshafts are just a few of the measures taken to prevent such occurrances.
In the end, its FAR cheaper to do these things proactively, than after the fact,....
08-09-2005, 10:47 PM
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Kim: Don't think I haven't considered it. Racing with you, Dean and Laura would be a hoot. Not to mention one of those sissy cars would actually force me to learn to drive better.
Steve: I'll keep that in mind. It's still a puzzle as I had kept the oil full (I'd been using about a quart per hour of track time) and the pressure was fine (up until it went ka-boom).
I'm not upgrading! I'm staying in stock/prepared class, this hobby is too damned expensive as it is! A description of my ka-boom was posted on 7/31 (the title was something like 1st race report).
Steve: I'll keep that in mind. It's still a puzzle as I had kept the oil full (I'd been using about a quart per hour of track time) and the pressure was fine (up until it went ka-boom).
I'm not upgrading! I'm staying in stock/prepared class, this hobby is too damned expensive as it is! A description of my ka-boom was posted on 7/31 (the title was something like 1st race report).
08-09-2005, 11:21 PM
#15
RL Technical Advisor
Originally Posted by Tom W
Steve: I'll keep that in mind. It's still a puzzle as I had kept the oil full (I'd been using about a quart per hour of track time) and the pressure was fine (up until it went ka-boom).
I'm not upgrading! I'm staying in stock/prepared class, this hobby is too damned expensive as it is! A description of my ka-boom was posted on 7/31 (the title was something like 1st race report).
I'm not upgrading! I'm staying in stock/prepared class, this hobby is too damned expensive as it is! A description of my ka-boom was posted on 7/31 (the title was something like 1st race report).
Its not a question of adequate oil supply, its an issue with all 911 engines at certain RPM levels.
Early short-stroke cranks could run to 7800 RPM without rod bearing problems, but these later long-stroke cranks have more trouble getting sufficient oil to the center two rod journals. In addition, the stock 3.6 oil pumps do not quite deliver sufficient oil pressure & volume at high RPM.
This is why we use the larger GT-3 oil pump, better rods (a well-known issue) and some bottom end mods to get enough oil to the center of the crank.
Its not about HP, its about long-term durability for track events.
I've only briefly touched on this subject, but hopefully this will help you in the rebuild so this will not happen again.