Surfing a round, I found a few threads on the topic here on the HAMB, but I came across this video yesterday. I know this is not a new modification, but the video is informative, but a bit long. I have not found a thread with this info on here, so I hopefully am not resharing old news. I'm looking to have this machine work done on a 261 I'm redoing for a friend and will post updates once I line up the machine work at a reasonable price. Seal part number is included in at the end of the video, the only thing I'm trying to confirm is the finished ID for pressing in the seal, i.e. how much interference fit should there be. Reading the mic in the vid, looks like they set it up for about 0.003" press fit.
The Jalopy Journal
