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Not sure when it happened, but I am guessing it was in Sunday’s race. I don’t think that explains the check engine lights and power issues on Saturday and Sunday morning, but one of the plugs is clearly fouled, so who knows.
Either way, I am replacing the rocker arm and crossing my fingers.
You probably need to double check according to several of the internet experts here that has never happened. You must be running a hot cam. Maybe it just looks like its broke.
I predict the next car to suffer this will be running a +100K motor that has had a history of lack of timely valve adjustments and is still running the original head. I’ve seen enough cases of broken rockers (on street & race engines) to form a theory that the cause is not high rpm operation per se. But rather that the cause is from repetitive impacts that result from lack of timely valve adjustments in the past coupled with worn valve guides.
Bill,
I don’t think the check engine and cutout on Saturday PM and Sunday AM was related to this. I think it’s related to the ECU as that’s what happened to my car in Sunday’s race. It took about eight minutes of running before the CE light came on and the car started cutting out. When I finally made it back to the pit I thought the motor was gone. When I changed out the ECU to give Eric/Julio theirs back the car started right up with no CE light, cutout, or any issues.
Bill tried our backup ECU as he was experiencing the CEL with his original unit. Jim tried our ECU as well but I’m not sure if it made a difference as he tried to diagnose his problems. What I do know is that our backup ECU works fine in our car - no idea why you both had issues with it. Jim may have some insight.
kchildre wrote:
[quote]Bill,
I don’t think the check engine and cutout on Saturday PM and Sunday AM was related to this. I think it’s related to the ECU as that’s what happened to my car in Sunday’s race. It took about eight minutes of running before the CE light came on and the car started cutting out. When I finally made it back to the pit I thought the motor was gone. When I changed out the ECU to give Eric/Julio theirs back the car started right up with no CE light, cutout, or any issues.[/quote]
That’s interesting…I tried their ECU and the car was backfiring and missing and all sorts of stuff. I switched back to mine and that went away.
The part I find most interesting is that for those first two laps before the engine broke, I had no CEL, no ABS light and the engine ran strong.
tpr jules wrote:
I can’t say that my car ran any better or any worse with your DME. There were other problems that I found and fixed this past weekend that negated any benefit from a DME swap.
For the curious, I found a bad crimp in the DME power lead from the main relay socket and that the fusible link in the DME power cable was corroded to the point that the fuse fell apart when I touched it. Interestingly, an ohms check of that cable showed nothing wrong. But a log of power to the DME showed a decrease with increasing rpm to the point that the DME was browning out.
That fusible link is gone and has been replaced by a 60a in-line lug type fuse mounted at the power block in the engine bay. Tonight I’ll find out if there are any other problems.
jlevie wrote:
Hmm. There really is a downside to racing 20+yr old cars. Pretty much every single little thing that you have not personally replaced is on the verge of failing. And here you sit doing nothing more useful then thinking “good god Jim logs DME voltage?”
Ranger wrote:
If Jim had long hairs in a pony tail, I can envision him melding and merging his ponytail with the wiring harness (à la Avatar) to sense the whole car’s operation.
Then again, I think I drank too much tea this afternoon.
Not ordinarily. I temporarily stole one of the USM analog input channels to see what power to the DME was doing when the rpm signal took a spike down to 300-600rpm. Right about the time the DME power input browned out to about 12.2v I’d see cutouts in the rpm log.
On R3V it has been said that I am an E30…
I am still leaning towards Mr. Robinson’s theory of a hot cam. You know what they say about trusting lawyers…
csrow wrote:
[quote]Ranger wrote:
If Jim had long hairs in a pony tail, I can envision him melding and merging his ponytail with the wiring harness (à la Avatar) to sense the whole car’s operation.
Then again, I think I drank too much tea this afternoon.[/quote]
jim doesn’t need ponytails… he’s a jedi master, he feels it through the force 
For those keeping count, I broke a rocker arm this past weekend during a DE event at Nashville.
I’ll be the first to admit that my engine is somewhere around 200K miles (odometer’s broke) and has been very reliable the past two years I’ve been running it. I write this one off as a “glad it held on this long” scenario.
thornton wrote:
[quote]For those keeping count, I broke a rocker arm this past weekend during a DE event at Nashville.
I’ll be the first to admit that my engine is somewhere around 200K miles (odometer’s broke) and has been very reliable the past two years I’ve been running it. I write this one off as a “glad it held on this long” scenario.
If the head has 200k on it, you might think about refreshing the head. Have the head guy take a hard look at your cam and remaining rockers and see what their condition is. Of the 5 or so heads that have gone thru my possesion in the last year, every one had worn out cam lobes and some worn out rockers (at the follower).
I’m no expert on the fatigue life of rocker arms. There is one school of thought that if they are properly adjusted on a OEM spec head, they don’t normally fail. But others disagree with this and I’ve no idea who’s right. The head on my spare motor has all used rocker arms. Those 12 that are on there were the pick of 3 different heads. Replacing all the rocker arms with new ones would be expensive. My perception is that most head refreshes don’t replace the rocker arms unless the followers show obvious wear.
I recommend replacing all of the rocker arms because they aren’t that expensive, around $17 a pop. Changing them at the track isn’t fun, but it is very doable. Broken rockers is a result of improper valve clearances. Don’t ask me how I know.
Another tip is to have your rocker arms x-rayed by a veterinarian.
My only broken rocker arm occured in a reconditioned head that I’d run for only a few hours of racing. But who knows the history of those rockers?
Refresh my memory - what are the indicators that it is a broken rocker arm? (before you remove the valve cover) sound? power?
Ran the Comp School at NJMP this weekend. Intended to run the races on Saturday and Sunday too, but early in the day my car sounded like a tractor and had no power. Kept running it as I had no time to pull the valve cover and check clearances. I was hoping the gaps had just gotten too large. Nope, a busted intake at #4 and a very loose exhaust at #5 (which I think is a cracked rocker there too). All 12 were brand new and properly adjusted less that 100 street miles before.
Do these things need to be checked soon after installation? Do they “break-in”? I’m wondering if there was just a bad casting and some voids in the rocker itself that caused it to fail so quickly.
I haven’t pulled the head off yet, but there is coolant sitting up on top there. So I’m assuming the head was cracked due to valve/piston interference. Hopefully the bottom end is ok…
