precup seals 602 engine ?
 

So does it make sense to try to seal a slight precup leak by tightening the internally splined retainer nut. I would rather not disturb the precup itself for a very minor leak. I may be missing something never having taken one of these apart. Cheers Dan

no.

the problem lies between the mating of the prechamber and the bore that accepts it.

as you said, it is a minor leak. Deal with it when you rebuild the head.

^x2

It could not hurt to try re=tightening it to the correct torque.

If you can find any there is more than a few threads on bubbling around the Prechambers when some liquid has gotten down inside of that area.
Most often the bubbles seem to be caused by something other than a leak. A reaction to vibration due to Fuel Injection (grab a hold of a Fuel Injection Line and you will feel it) and heat seem to cause them if liquid is down there.

If you actually have a Prechamber leak gas ought to come out at some velocity during ignition.

Also on Diesels Carbon tends to fill in tiny leaks.

Bigger more obvious leaks can actually burn larger.

If you sprayed a mixture of Dawn Dishwashing Soap (My Wife uses that in here Pre-school class to make bubbles) and Water on a cold Engine do you think it would bubble? If there was a Prechamber Leak you might see a large bubble or a growing pile of little bubbles and it might give an idea as to how big the leak is.

good idea
 

I will try this thanks
" If you sprayed a mixture of Dawn Dishwashing Soap (My Wife uses that in here Pre-school class to make bubbles) and Water on a cold Engine do you think it would bubble? If there was a Prechamber Leak you might see a large bubble or a growing pile of little bubbles and it might give an idea as to how big the leak is."

If everthing is cold it also works on Exhaust Leaks and Intake Manifold Leaks if there is Boost Pressure in the Take Manifold.