I'm installing a Diesel Dynamics camshaft while I have the engine apart... I'm replacing all the piston rings as part of the rebuild. DD tells me that the first step for break-in of the cam is this:

"At first start-up run engine at 2000rpm for 20 mins."

My question is, will this be detrimental to the seating of the piston rings? I've been told in the past that constant rpm for an extended period of time is bad for break-in on these engines...

Thanks.
~ Russ

 

Ask DD.

 

No, it will be fine, steady RPM for a long time is detrimental to ring seating on any motor. I have built tons of motors with new rings and a new cam, just keep it at the steady RPM in the driveway to break the cam in, DO NOT let it idle until the 20 minutes has passed. Then take it out and drive it and vary your speed to seat the rings, and don't run it too hard. 20 minutes is not an extended period of time, just don't take it on the freeway for a 100 miles. It will blow a little oil until they seat, you did hone the bores, right??

Tom

 

Gee... why didn't I think of that! ... I'm still waiting for a response from DD.

 

Thanks Tom, and no, I didn't hone the bores... aside from the cylinder that was repaired (obviously). They're all in good shape and the guy who sleeved the cylinder felt the same way so we left 'em alone.

~ Russ

 

You should be OK, although I have never done that, I have seen it work.

Tom

 

You should cross hatch hone all the bores as that will help speed the process and seat the rings better/faster.

 

So how many miles does it usually take for the rings to seat?

 

Cummins Site says 5000. And not to use synthetic oil during this period. How about that!

 

It should start to seat at about 1K, fully seated at 5, and AA Meeting is correct, No Synthetic oil!!!!

 

I'm well aware of the "no synthetic" rule... thanks for the other info though.

 

Just dont let it idle very long.. keep the rev's up a bit.. Get out on the highway and mash the pedal a few times and your rings are seated.

sit back and enjoy.

If they take 5,000 miles to seat, you either got some washed cylinder walls that didnt get honed/hatched or the rings are crappy.