- Engine:
- 3412 (S/N: 3JK1-UP)
- 3412C (S/N: 3JK1-UP)
Description of Change: The correct optional cylinder head has been added for use on certain 3412 and 3412C Marine Engines in high horsepower applications.
The valve mechanism was updated to include valves made from a high nickel alloy and floating valve bridges, that do not ride on dowels.
Note: Ensure that the correct valve mechanism group is installed when installing the optional cylinder head on earlier engines.
Adaptable To: Valve bridges may be required for engines that have serial numbers 3JK1-875 which were originally built with guided bridges. Refer to Illustration 1.
 | |
| Illustration 1 | g03049616 |
Old valve mechanism (1) Dowel | |
 | |
| Illustration 2 | g02159880 |
New valve mechanism without the dowel | |
When replacing an old head with the updated head, a different valve bridge is needed since the updated head does not have a dowel hole. Refer to Illustration 2. For a more detailed description, refer to Engine News, SEBD9258, "Be Sure to Use the Correct Inlet and Exhaust Valves in Engines Equipped with Valve Bridges that Do Not Ride on Dowels".
The valve mechanism is adaptable back to the first production of the listed engines. The change is effective for serial numbers 3JK875-UP.