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Statistical  Look Number 3

new 1/18/03, updated 1/31/03

I have been doing some house keeping,  Here is a tally of cam failure reports. Information is incomplete as you can guess. Average mileage at failure is 75,008. We have several double failures and two triple failures.

Histogram looks like this: 

30,000 bar would be that group greater than 25,000 and less than 30,000. 

Note while average may be 75 the risk below 50k is still very real. 

We lack mileage information on 41 failures, yet the 127 data points do indicate the bulk of failures occur before 100k. One cam failure at 145k indicates to me you are never safe. 

I don't want to take this too far, it may be unlucky (for your cams ) to have a first name that begins with "B", "J", "D", "K", "R", "S", "T" or "W".  This is the best accounting I can give at this time with the "Body Count" standing at 188.


The statistical charts seem to indicate that if there is going to be a problem it will occur before 100,000 miles. Some things could be distorting the picture, those of us who have had our cams welded or pinned. It would be interesting to see the charts by year. It would also be interesting to see if there are very many people out there with over 130,000 miles that have not had a failure and have not modified their cams.

Best regards,
W. Jay Kellogg


I don't know if we have enough information to break out the years, compare them and conclude anything meaningful. Forgetting totaled cars the population by year is 96 25%, 97 50%, 98-99 12.5% each. Assume a 15k mile offset per year in usage. Because 96-97 are coming into their most veranable (sp?) time I expect this to be a banner year for failures.

We have less than 200 owners who have fixed their cars.  I can try to contact owners who failed to report miles at failure (again) but in a way it does not matter. If, as I expect, we know about 1/10 of the failures - once we contact all 20,000 owners and have say 2,000 failures to work with we will have all raw data one could need. 

We have enough data to demonstrate a pattern of early failure. That is all we need for a jury or judge.  As one would expect we are getting more reports of double and triple failures .in a small population. So much for rare.


Taking into account the most recent cam failures we have 202 reports, of which only 138 tell us the mileage at failure.

I get an average of 74,820 with a std dev of 23,899 miles.

Why not call it 75k +/- 24k, anything over 50k you are at great risk. 

87% ~ 119 or of 137 occur between 40k - 100k. 
3% ~ before 40k
10% after 100k

Distribution is not normal, it is a time related distribution with a big peak between 45k-100k and a long tail with as miles increase.

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