Originally Posted by
spaceworm
A workaround for engines without a pinned ring was a bridge across the port(s). Some hop-ups include removing the bridge when using a pinned ring to replace the stock one. Removing the bridge increases the flow; replacing the ring with a Bowman pinned ring increases the performance due to improved compression from better sealing rings and and reduced ring blow-by from smaller ring end gap.
While true, most of the ringed engines with pinned rings I've had apart have a bridged exhaust port. One has to consider the transfer ports as well - many liners I've seen have transfer ports that are longer horizontally than they are vertically. While the exhaust port is often the widest port, that isn't the only one that would be wide enough to snag a ring. In the case of my Fox .50 and likely most other B-case Foxes, the transfer port is split into two narrow ports running vertically at an angle as well as having a bridged exhaust port.