Mas
Lieutenant Commander
- Joined
- Oct 3, 2006
- Messages
- 1,656
You do have the compression relief valves in that '57 powerhead, but they cannot be used with the '56 rewind starter which does not have the activation cam or arm (which both are missing also). The decompression valves are designed to momentarily reduce cylinder compression to aid in rope starting so you do not wear yourself out. The motor must be properly tuned, however.