I’m running an M20B25 with factory parts. I didn’t grow up driving manual, so 99% of the manual driving I’ve done has been in this car at speed.
In January, I money shifted at high revs, 3rd to 2nd instead of 3rd to 4th. I got the clutch in quickly, so there were no catastrophic or terminal parts failures at that moment.
Fast forward to June after a few lapping sessions and a full race weekend. Halfway through my 2nd race weekend with it, one of the rocker arms broke mid-race with no obvious over-rev. I replaced it and carried on. The 4th race weekend, a different rocker arm broke, again without any obvious over-rev. Just yesterday, another one gave out, so I’m going to replace all of them.
All 3 failures have been on the intake side, but I believe that’s just coincidence. Valves have been lashed to 0.010” each time. Oil has been changed regularly.
I suspect that there are hairline fractures in most of the rocker arms from the money shift in January and that the failures are now rearing their head one at a time, but I’d like to confirm that suspicion both by running it by the group as well as doing a thorough inspection of the remaining rocker arms from the incident.
My greater concern is that I’m actually causing isolated failures in each of these instances with my driving style. I don’t believe I’m shifting irresponsibly, I heel-toe and try to rev march as best as I can, and I’m not super aggressive with upshifts. I guess I could be more gentle on the clutch release? But even then, I don’t feel like the rocker arms would fail so regularly because of a clumsy upshift once in a while.
Any thoughts would be appreciated.
In January, I money shifted at high revs, 3rd to 2nd instead of 3rd to 4th. I got the clutch in quickly, so there were no catastrophic or terminal parts failures at that moment.
Fast forward to June after a few lapping sessions and a full race weekend. Halfway through my 2nd race weekend with it, one of the rocker arms broke mid-race with no obvious over-rev. I replaced it and carried on. The 4th race weekend, a different rocker arm broke, again without any obvious over-rev. Just yesterday, another one gave out, so I’m going to replace all of them.
All 3 failures have been on the intake side, but I believe that’s just coincidence. Valves have been lashed to 0.010” each time. Oil has been changed regularly.
I suspect that there are hairline fractures in most of the rocker arms from the money shift in January and that the failures are now rearing their head one at a time, but I’d like to confirm that suspicion both by running it by the group as well as doing a thorough inspection of the remaining rocker arms from the incident.
My greater concern is that I’m actually causing isolated failures in each of these instances with my driving style. I don’t believe I’m shifting irresponsibly, I heel-toe and try to rev march as best as I can, and I’m not super aggressive with upshifts. I guess I could be more gentle on the clutch release? But even then, I don’t feel like the rocker arms would fail so regularly because of a clumsy upshift once in a while.
Any thoughts would be appreciated.