excessive blow by a concern?

My old D47U has what i would consider a nontrivial amount of blow by. Engine runs fine and I could swap in cylinder kits but would like to use it over the summer. No weird noises or anything. Should I be concerned and save it for a fall task?

Has it been worked hard lately for a period of time at operating temp? If not that may help/eliminate the blowby.

Does anyone still do the BonAmi treatment to an engine??

Worn valve stems and guides will make have blow by also.

would it be safe to assume if this was the major source it would be very visible from the valve cover off?

if it has enough power and doesn't overheat or use more than a gallon of oil in a ten hour day then i would run it.

If its a steady stream that would suggest general wear ,pulsing would be more concerning as that could mean one cylinder is damaged and could cause a bigger problem..

Not seen it lately you would need to be sure you had bore glazing and not wear , mainly works on a engine that wasn't broken in corectly or hadn't
been honed enough for new piston rings to seat I think ...

I would agree with all the posts earlier, except that the chances of having much blow by from valve bushings has got to be low.

I think your engine is telling you it has lots of wear and I would be very careful about oil condition and pressure, even more than normal until you get it rebuilt. The results of bearing failure are invariably expensive. If the pressure is good I wouldnt worry about running it, but would certainly be checking for any tendency to (apparently) not burn oil, or to "make" or gain oil. Either one points to some degree of fuel contamination which needs to be caught quickly or at least the oil lubricity closely monitored if it is just not using any.

High clearance bearings cannot withstand compromised lubrication.