Van Norman 777-6, Serial # 3989 boring outboard engine blocks

[Lawrence Thornton]

Have a 777-6 that is used for both automotive boring & for Outboard Engines. When boring an outboard block with ports in it, (interrupted cut) there is a very loud clack / knock, etc sound as it goes by the ports. I feel that I have some major wear or possibly something is out of adjustment . Any and all help is greatly appreciated.

 

[Turbowerks]

Never ran a triple 7 but many others, pop the cover check the drive keys that slide up and down , or splines whatever that has. Could be a worn key or gear that it slides in. My old storm does that too, just a very experienced bar.

 

[Dan from Oakland]

How heavy a cut are you taking? There is backlash through the gear train and there are a pair of gears in the upper housing, driven by the vertical drive rod that is parallel to the main bar. The key could have slop, and the upper gears can be worn- have you greased the upper gear box? If you do a lot of ported cylinders, and heavy cuts, make up a small flywheel and mount it on the top of the bar over the split collar. Have you tried putting drag on the top collar with your hand when the bar is running? does that eliminate some of the clacking? Another solution may be a spring loaded friction block on a small cylinder at the top to keep the bar loaded. Just some thoughts for you to consider.

 

[Limy Sami]

+ 1 on Dan from Oakland creating drag, .....back in the day when I was reboring Spanish 2 stroke trials motor cylinders on an old and well worn 10'' Logan lathe, I hung an old leather belt with weight on the end over the chuck** body to create drag and take the knock out of the back gear train.

Plus, IME with ported cyls you need lighter cuts.

** Just for clarity, the cyls weren't held in a chuck, their fixture was!

 

[Lawrence Thornton]

Have a 777-6 that is used for both automotive boring & for Outboard Engines. When boring an outboard block with ports in it, (interrupted cut) there is a very loud clack / knock, etc sound as it goes by the ports. I feel that I have some major wear or possibly something is out of adjustment . Any and all help is greatly appreciated.

We have put a little drag on the top collar & this does help. Will open up top gear set & check/ replace key & gears. Thanks LT