Posted by Matt G on July 06, 2001 at 07:03:53:
In Reply to: Porting of valves posted by Charles Knight on July 05, 2001 at 21:15:34:
Charles,
Those valves are actually vented and not ported. The small hole drilled in the casing of the valve allows air to escape when the slide is moved without the valve depressed. This makes the horn "popless" when a valve slide is moved in preparation for the next tuning adjustment. Matt Walters did the job on that valveset so you might want to contact him with any questions. These valves were plated before the venting process, so the actual compression of the valves should not be a problem. However, the slide pop test will not let you know how the compression is. The main reason these valves were vented was because the first slide on Marzans needs a good bit of manipulation. If the job is done well, which I'm sure it is, there are rarely any negatives to this process.
Matt G