Hello Socal Jetboats!

Long time watcher/reader, first time poster.  I have just purchased the family jetboat from my parents who have owned it since 1999, a 1974 Bayon with a 455 and Berkeley jet.  The boat has been well maintained since my families ownership.  Naturally, during my second time out, the 455 decided to let go with a spun rod bearing in cylinder 8.  this occured during a 2k RPM slow cruise back to the beach.

With the above being said, I've pulled the 455, stripped down to a long block and have just dropped it off to the machine shop for the rebuild.  Below are my goals for the rebuild, what I've already planned for the build...and what I am looking for input on from any olds experts.  Interested in your feedback.

Details of boat:
- 21ft 74 Bayon (unsure specific model)
- Berkeley JC pump, original impeller A
- Seats 6
- cruiser hull, semi-V bottom (definately not flat)

Goals of build:
 - Solid, reliable 455 which will last
 - Around 5 or 5500 max RPM
-  Around 350-375hp, 400 ft. lbs.

Already planned for engine build:
- Oiling mods for the 455
- Milodon 7 quart oil pan (upgrade from OE)
- Upgrade to Hardin logs/snails from the Berkeley Packajet stock manifolds
- Edelbrock performer intake manifold (replacing stock cast iron)
- Increase compression while remaining on pump gas (91 octane)
- Upgrade to better cam

Questions:

1. Cam: What do folks recommend?  My goals are a moderate build with increased power (as listed above)...but nothing crazy.  Seems more lift/duration would be the best fit (with minimal overlap), but interested in first-hand opinions.
2. Impeller:  While having the engine work done, I plan to rebuild the pump and replace the impeller/wear ring.  Boat is currently setup with an A impeller which has been a good match with the OE setup.  Considering the above proposed build, any recommendations on an impeller pitch change?

Thanks for the input! 

Goals of build:
 - Solid, reliable 455 which will last
 - Around 5 or 5500 max RPM
-  Around 350-375hp, 400 ft. lbs.

Already planned for engine build:
- Oiling mods for the 455
- Milodon 7 quart oil pan (upgrade from OE)
- Upgrade to Hardin logs/snails from the Berkeley Packajet stock manifolds
- Edelbrock performer intake manifold (replacing stock cast iron)
- Increase compression while remaining on pump gas (91 octane)
- Upgrade to better cam

Questions:

1. Cam: What do folks recommend?  My goals are a moderate build with increased power (as listed above)...but nothing crazy.  Seems more lift/duration would be the best fit (with minimal overlap), but interested in first-hand opinions.
2. Impeller:  While having the engine work done, I plan to rebuild the pump and replace the impeller/wear ring.  Boat is currently setup with an A impeller which has been a good match with the OE setup.  Considering the above proposed build, any recommendations on an impeller pitch change?

Thanks for the input!

Ok, where to start....

- what machine shop did you take it to?  Are they familiar with marine engines?

- The HP you are looking for and the RPM with an A impeller do not match. 375 HP will get you basically 4900 give or take. Pretty easy to do. i would stick with the A impeller.  Depending on your driving style and weight of the boat, you might get away with going with an AA impeller for better cruise speed.  Even at 375 hp you will most likely be in the 475 TQ range anyway.

- What Head casting letter do you have?  (please dont say J... please dont say J.... please dont say J.... please dont say J)

- I have built some olds with TRW pistons - (would not recommend) too heavy.  I have built some olds with KB pistons (would recommend) lots lighter, good price and taller height for better quench/compression. there are other brands as well, your machine shop can recommend also based on who their vendors are.

- Oil pan, personally i would skip the 7 qt and just go straight to the a std 10 qt marine pan. you need oil volume to keep oil temps in check just as much as total volume for the engine.

- Cam - we were aggressive with our cam with logs but never had reversion problems.  236/248 Engle cam.  madew 457 HP with headers but only 425 hp with the logs on the dyno.  Id say you will be looking for something in the 226/232 range.  we can talk cams later though.

- compression - depending on final cam selection you will most likely be looking for the 9.3 to 9.5 range and be safe on 91.  again we were aggressive and were 9.8 on 91.

- Performer intake will be perfect for this setup.

- Please describe oil mods you plan.  there are quite a few!

- What are your plans for valvetrain? 

-what carb was on the engine?  are you planning on keeping it?


- Most importantly, what rpm did the original motor turn?  were you happy with the performance?  what are the current cam specs? is there any engine tags on the current engine with original HP rating or anything?

waiting your response, Olds 455 was my first engine i ever build from scratch, i have a special love for them.