"Break In" Oil for Rebuilt K-Series Engine?
 

I'll be rebuilding a K321 soon, including piston and rings. Is it a good idea to use the break-in oil sold by some of the big names? I'm also considering using Valvoline VR1 Classic Car oil for the long term, mostly because of the higher zinc content.

A few years ago I did a total rebuild on another K321 and the rings didn't seat well right off the hop. It always blows blue on start up, but that might be more to do with the aftermarket rings though. I'm not sure now what oil I used after the rebuild, other than it was straight SAE 30 weight.

There is always a debate about detergent and non-detergent as well.

Hello , this will help.

https://www.onlycubcadets.net/forum/...ad.php?t=54255

I usually use generous amounts of royal purple during assembly and add the reg 30 wt oil , fire it up and get it hot shut it down,let it cool and re torque the head at least 2 or 3 times with the heat and cool cycle and after an hour or two of run time drain the oil and refill with fresh 30 wt then run it like you stole it ! :beerchug:

Pretty much the way I have done things as well. Especially the
re torque and then the re torque and...... I have just gotten in the
habit for re torque on these heads every year. They are always loosened
up a little it seems.

I have always used Non detergent 30 weight all the time. It is
getting pretty tough to come by around here anymore though. So will
have to do something else pretty soon.

Ken

Did you replace the valves and guides during the rebuild?

I ground the valve and seats and the stems measured good. But due to a misunderstanding with the machine shop that did the boring, the guides did not get changed and I didn't realize that until near the end of assembly and fast approaching spring.

I'll order two sets of guides, one for that engine and one for the intended rebuild. I may just change the guides in the past rebuild, since it can be done easily in the tractor, or I may pull and dissemble it and do a deglaze and re-ring if time permits.

Thanks for the link Darkminion. That's pretty clear and concise!

its best to work the engine when seating up the rings. Especially important on diesels, but also on gas engines. Running the mower deck, even if not cutting grass puts a good load on the engine. Run her up to full throttle, if you have a electronic tach, adjust throttle/gov so you see 3600rpm with the mower deck engaged and let her run for an hour or so. That will seat up the rings nicely. Drain the oil while still hot and put in whatever your flavor of normal oil you plan to run.