Broken Cam Epidemic?
#1
Drifting
Thread Starter
Broken Cam Epidemic?
Just discovered that the drivers side cam on my 78 was broken inside the gear. This is on a 17 year old crate engine that was installed in 91. Tom Charlesworth (PCA guru and Tulsa mechanic) indicated this is the 3rd cam to go this summer in the Tulsa area. The timing belt had never been overtensioned in the 8 years I've owned the vehicle. All the rollers, tensioners, etc were in good shape. Metal fatigue? Is this unique to this area and if so, could it be the water?
Dennis
Dennis
Last edited by Dennis Wilson; 09-16-2008 at 02:03 PM.
#2
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The cams are quite brittle and surprisingly easy to break.... usually it is the drivers side with the longer unsupported snout... We have sold a LOT of cams over the last 20 years ...
#4
Drifting
Thread Starter
Jim,
I had a brain f@rt. It was the drivers side. Did Tom order the replacement from you?
Dennis
#5
Drifting
Thread Starter
Sterling,
You'll have to ask 928 Intl about that. All I have is a copy of their invoice to a PO. I had checked the tension since the last belt change and it always came up on the loose side of the notch on the JK tension tool.
Dennis
You'll have to ask 928 Intl about that. All I have is a copy of their invoice to a PO. I had checked the tension since the last belt change and it always came up on the loose side of the notch on the JK tension tool.
Dennis
#6
Drifting
Thread Starter
Discussed the 3 Tulsa area broken cams with Tom today and there were 2 common factors in all three breaks. 1} All were older engines with the halfmoon woodrift keys/cuts and 2) all were using Mobil 1 in the new low zink formula. He has also seen a broken shaft on a GT's oil pump which was using Mobil 1. Over tensioning was not a factor.
Dennis
Dennis
#7
Race Car
Discussed the 3 Tulsa area broken cams with Tom today and there were 2 common factors in all three breaks. 1} All were older engines with the halfmoon woodrift keys/cuts and 2) all were using Mobil 1 in the new low zink formula. He has also seen a broken shaft on a GT's oil pump which was using Mobil 1. Over tensioning was not a factor.
Dennis
Dennis
Dan
'91 928GT S/C 475hp/460lb.ft
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#13
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Woodruff depth maybe. But without imbalance and undue tension on the cam, or MORE LIKELY some sort of impact at some point, it seems unlikely a cam would break. Many thousands of cams run many quadrillions of miles with no issues, and we're looking at what ..a sample of 3? 10? 100? Out of how many cams, thousands...
#15
Drifting
Thread Starter
Woodruff depth maybe. But without imbalance and undue tension on the cam, or MORE LIKELY some sort of impact at some point, it seems unlikely a cam would break. Many thousands of cams run many quadrillions of miles with no issues, and we're looking at what ..a sample of 3? 10? 100? Out of how many cams, thousands...
Actually, the jury is still out on what caused it but I will be changing to a high zinc oil on all of my cars, especially the 928 and 931.
Dennis