rebuilt 8.1's - break in period/oil consumption

I still have a couple of minor nagging issues which I have in separate threads below, I will come back and close those out. All told, I've put 41 hours on the rebuilt 8.1's and wondering if I should be concerned about the oil consumption. I might have mentioned this in a prior post, I have a feeling I wound up idling these at home a little longer than I should have. I pulled one plug and the cylinder wall didn't have a shine to it which is good (concern would be cylinder glazing).

I'm just wondering how long the entire break in process takes? I seems like I'm topping off constantly but I'm also checking at the beginning and end of each trip so it "feels" I'm wearing out the dipstick:

- over the first six hours, I used 1 QT on STB and 1.5 QTS on PORT. I did my 1st oil/filter change at 9 hours. Since then, (another 32 hours) I have added a total of:

STB - 2.5 QTS
PORT - 1.75 QTS

Does that seem excessive? Should I run the harder/closer to WOT for longer periods of time? Everything I've read about cylinder glazing says that if it's already an issue, there's nothing you can do at this point. I just don't know if a marine engine needs a much longer break in period than say a car where you can rack up the miles. Even though I have roller cams, my first start was around 2,000 RPM's for around 20 mins and varying RPM's. I had a bunch (6?) of quick runs to test various issues but they never idled for more than a few mins and I always revved them up/down. I'm doing another oil/filter change now and will log everything again.

Maybe they just need more time, curious what you guys think.


Bob

1) I also have 8.1 engines, four years old now and noticed high oil consumption first two years. Has slowed down the last two years to about 1/2 quart per 40 hrs of use. I think it is normal to see high usage of oil on the new engines. Wait until at least 300 hrs or so, and I think you will see a big change."

2) Keep an eye on your oil levels and break in the engine as per your owners manual. The engines will use more oil during break in, but should stabilize after about 100 hours. Put in a call to Crusader, expressing your concern, but don't panic until after break in.

3) I have 2 new 8.1 MPI 385hp crusader engines in a new motor yacht. They only have 30 hrs. on each engine. The port engine has used one quart of oil but the starboard engine has used 3 quarts. I think I may have a serious problem with the starboard engine. What do you think ??

- a couple of random comments I found in an 8.1 oil consumption thread here from 2007. Glad to hear that maybe I just need to rack up a whole lot more hours.

with the roller cam, you didn't need to to the 20 mins @ 2K but I doubt that hurt anything.

The Factory O&M manual says oil consumption should stabilize around 100 hours...

first question: what did the machine shop tell you to use for oil?

second question: have you looked for minor leaks on each engine?

I think they are consuming a bit more oil than I'd like to see but it is still 'early'...

When we had the 8.1 in the GM light and medium duty trucks they always consumed more oil than the 7.4.Engineering told us it was due to a pcv system change that instead of a valve it was a fixed oriffice hole in the bottom of the intake.We changed pistons on a few and it made no differance.It is what it is and always check your oil level.Dont know if the marine engine has the same setup.Can you see a pcv valve in the valve cover?

I held off replying because I took my longest trip of the season and have some better data. Now, I think I only have one problem, not two. Over eleven hours running, with hours at 3,700 RPM's, my port engine didn't use any oil. This was just after an oil/filter change on both sides. The Port engine used a QT over the same period. I've been in this adding/checking cycle so I'm happy that both engines seem to be trending downward. I have 52 hours on them now since the rebuilds.

Mark to answer your question, yes I do have a leak on this engine. Going back to the winter, this was the debacle with the machine shop not using enough RTV on the rear main cap. I fixed that issue on the PORT side and convinced myself it was ok on the STB side. I believe it only leaks when it's running which makes sense. In reality, maybe 1/2 of my consumption is leaking and the other 1/2 being burned which wouldn't be a big deal and maybe that side slows down as well.

I'm probably not going to pull it just to fix the leak, at least not yet. I suppose I could lift it straight up, drop the pan, pull the cap, etc. and then reinstall.

On my initial break in run, I knew I didn't have to break in the cam but sort of followed the process just to keep the RPM's up and then varied. I probably ran them both about the same number of hours before the install. After this last run, I'm a lot less concerned about cylinder glazing as I was a few weeks ago. On the oil, I told the machine shop that I run Rotella 15w40 and they said that would be fine just no synthetic during the break in period. I changed it at 10 hours and then at 40 and will do one more year end change which probably won't be more than another 20 hours.

Stach454 - there is no PCV valve but I read that was an issue. GM/Crusader actually issued a bulletin to upgrade the intake manifold bolts for exactly this issue which I did.

We have done many of the updated bolt repair bulletin and all I can say is don't waste your money.Dont bother with purchasing new bolts but it may be a good idea to check the torque. I have yet to see that bulletin repair make a difference on any of them.With the fixed orifice style pcv its going to consume more oil.Dont read to far into this just keep an eye on your oil level.Good luck.

shouldn't be any issues due to the rotella...and it sounds like things are improving...at least on the Port side...

did you fuel economy change any on the long trip?

Indirectly yes. My floscans indicated my fuel burn around the same but I seemed to be about 2 knots faster on this trip. I did have the tide in my favor for part of the leg but not all. I was 21k+ pretty much the whole time where previously I was around 19k. With the old 454's, I was 16k-17k at best burning the same 32GPH.

It suddenly "feels" like I have more torque, maybe the compression has ticked up slightly as they break-in more? I have a shorter trip planned later today but I'll be up on plane for about 30 mins. I minor thing which is a huge PIA is the oil fill location. No more adding through the valve covers on the 8.1's which means I have to pump the oil in, I have a wetbar and bench over each hatch. Not a big deal once I'm doing it less.