Quote: I have been reading everything I can on the 340 valve train and just read that the 340 rockers were different than the 318 rockers. Apparently they have a relief area for bigger valve springs. I didn't realize they were different. I used a set of 318 rockers! Haven't been able to go out and confirm this is my problem but can anyone confirm if this is truly the case? Were the rockers different? Could this be the cause of my noise?
When the 340's came out in 68 they used 318 rockers with larger diameter springs and retainers. They DEFINITELY had interference issues. The problem was corrected sometime early to mid 69. They corrected it by grinding a relief on the backside of the rocker during manufacturing. I believe all the rockers from that point forward (318/340/360) all had the relief in them. If one is using a set of early rockers it would be best to swap them out or at least check them. This issue can also be present when using 273 rockers. Congrats on finding the issue, that could have been disastrous. As to the cause I'm going to bet on a manufacturing defect
