Is that too much blowby on a Cat 15 liter engine?

The fact that you can see it blowing drops of oil out say it is too much.
You can likely just put liner and pistons in it if you’re trying to get by cheap but there’s also a decent chance the block will need counterbored. Possibly also going to find high amounts of wear due to soot contamination in the oil….depends on how long it’s been that bad.

 

Is this blowby new? If you have had a recent large increase you could have broken a ring or have fuel dilution in the oil. How's your oil pressure?

I had an PAI ceramic coated piston rebuild kit. Lost a wrist pin after about 150k miles. All of the pistons were kinda wobbly in the bore and in wear areas the golden ceramic was black both on pistons and bearings.

I replaced with an oem cat kit and never looked back

As for your blowby

I have a recommendation before you rebuild. When you change oil next. Add a gallon of marvel mystery oil to the crank case and run it for a little bit. Idle for 30 min. Best if you can run around without a heavy load on it for an hour or so.

Also run a few gallons of marvel mystery in your fuel at the mix ratio on the bottle.

In my experience it really helps clean up carbon and sludge on the quick.

Instead of adding Lucas. Add a gallon of cheap non synthetic 80-90 gear lube to the the crank case. Whenever you top up. And also at oil change.

It will smell horrific out the blow by. But again. In my experience works much better than Lucas at reducing blow by and leaks.

 

Blowby is only measured under a load on a dyno. Idling and seeing vapors and/or oil coming out of the vent tube could mean other issues and won’t indicate a problem with the rings.

 

Pulled in to one of my direct customers last year and noticed a big puddle of oil under my truck, it was blowing enough you could feel it on your hand at idle, and I don’t mean gently.

Oil was bypassing the accessory drive seal it had so much crankcase pressure.
Found a cylinder with broken rings on the piston. Cylinder was scarred letting the compression into the crankcase.

Not saying this is your problem with your truck, just saying what potentially can happen….

 

At your next oil change, just for giggles, change to a different brand of oil. Also consider instead of the 80-90 thing, try a straight 30w heavy duty diesel motor oil. It’s summer time, the 30w won’t hurt a thing.
Before everybody jumps in my chili about how much better oils are than decades ago, when 30w & 40w were the norm, that’s true, but straight weight oils are also vastly improved from decades ago.

 

Had a 3406B doing that shortly after an inframe. Screen in blowby housing on top of valve cover was plugged up. Assumed mechanic overlooked that. Replaced it but had the same problem in a week or two. An exhaust valve guide had 1/4 inch side play.
Saw a DT with a bad turbo doing worse than yours.
When I worked for large fleets they went more so by oil consumption. Is it acceptable?
Just some things to thank about and check.
How far do you get from home. Taking chances far from home can be very expensive.