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CarlH

Break-In Procedure

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CarlH
I just got the Lombardini diesel in my 7790 rebuilt and running:). Now I need some advice on a good way to break it in. The service manual talks about (in poor English) two parts of the 'run-in' process. The first is an 'idle test'. Run the engine no-load starting at 1500 RPM for 15 minutes then increasing the RPM by 300 RPM increments and running at each RPM for 15 minutes until max RPM. The second part is progressively increasing the load for the first 10 hours not exceeding 70% of rated power. The first part is straight forward, although a bit time consuming. The second is somewhat more difficult to implement precisely. Does anyone have a practical procedure given the loads I am able to impose on a garden tractor? Essentially the only load I can really apply is mowing for some period of time. Also, any recommendations on initial oil change interval? Thanks.

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HubbardRA
Carl, If I were you, I would go thru the idle break-in procedure, then skip the second part and go straight to using the tractor. I wouldn't be towing three food diameter logs out of the woods for a while, but normal usage, mowing, tilling, etc., will never load the engine to 100% capacity. Use these comments as you wish. After all, I am only an engineer, and I gotta keep an eye out for you to start shooting. LOL

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HubbardRA
Last two gasoline engines that I rebuilt were used from the start with no break-in, other than a few minutes of idling and carb tuning. I tried to use them pulling carts, and dragging things around, with the speed being varied quite a bit, before I put a deck under them and cranked up the throttle to mow the lawn. In both situations, i needed to mow long before I had run through any significant break-in period. Both were B/S engines. Both run strong, and neither used any oil at all last summer. Guess the lack of a break-in period didn't hurt them.

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B.Ikard
Carl, You are going to get advice that runs the whole spectrum so be prepared.....and I have met a lot of sharp engineers mainly beginning their career in the field at the grass roots level instead of wearing a tie in an office :) That being said, I worked in an overhaul depot several years ago, probably put together 100 or so large to larger Cat, Cummins, and Detroit engines primarily for generator sets and heavy equipment. There was a complicated lengthy schedule of dyno loading to break in, probably to determine if an engine would carry rated load and if it was assembeled correctly rather than to actually establish wear surfaces,etc. I'd get one together, run @1800 for an hour or so, correct any problems and crate it.... I had a very few engines come back because improper grade/ viscosity oil was used (Detroit 2 Strokes). On my personal equipment and jobs, after this hour unloaded run I would use normally, just do not lug hard and overwork till you get 50 or so hours on it. IMHO people get all wrapped up on the mysteries of ring seating and oil consumption. Bottom line if you have excessive oil burning/consumption problems after a few hours operation something went wrong with the overhaul. Ike

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Ryan
Rod, that is kind of a joke between the Mech. Eng. and the Man. Eng. down here at school. I have a lot of respect for any kind of engineer. It is a lot of hard to get through such a program. I am sorry if I affended you in any way. It was all in fun.

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HubbardRA
Ryan, I am just joking also. Just keep forgetting to put LOL after the statements. You know us old engineers, who suffer from CRS. Wish I could remember what that stands for.

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jlasater
In the motorcycle field, there's a saying about breaking an engine in hard. Very lightly loading it right after a rebuild tends to cause the rings not to seat very well. Doesn't mean run it around at redline, but idling it is bad news and is considered so by most engine builders. Stay away from any synthetic or semi-synthetic oils during the break-in period as well. You can switch to them after break-in is finished. >> Found the phrase: "Break it in fast, and it'll be fast. Break it in slow, and it'll always be slow." It applies to more than just motorcycles.

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Roy
As another engineer let me throw this into the conversation. Cast iron rings seat easily while chrome rings need to be run hard and hot to seat. Thus it seems the break in procedure should be dictated by the type of rings used for the rebuild. My 2 cents worth, Roy

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CarlH
Another perspective is what is recommended for Perfect Circle rings in automotive applications. After initial startup and adjustment, take the car to lightly traveled road. Accelerate WOT in high gear from 20 MPH to 60-70 MPH, coast down to 20 MPH, repeat 7 - 10 times. I have done this with several car engines after I rebuilt them. After the first 3 or 4 runs, the car accelerates noticeably faster. A very good mechanic explained that this is a combination of varying the load on the engine with it hot and sufficiently stresses the engine to get everything broken-in adequately, or broken, if not built correctly :D ! Thanks to you all for your inputs.

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