Fly in drive home question

[roaniecowpony]

I think it's two points you are mixing together. But the short answer (for me, anyway) to your question is "every wear surface" in your vehicle needs to be seated. Granted, they put new motors on a dyno before dropping into your new vehicle (that starts the rings/bearings seating) but that process needs to be completed to somewhere between (reference only) 300 and 500 miles. All machined parts have imperfections (high points) that need to be worn down, or seated. That includes the engine, tranny, transfer case, rear ends, brakes, etc. Hell, I don't even fart in my new seat for the first 500 miles, but I probably should, at least little ones.

My other point is that I do not, nor should anyone else, "baby" their new vehicle. Drive it like you stole it, but only up to around 4,000 rpm. There is plenty of data from torn down engines that show improper wear of parts that were pushed above that threshold during the break-in. 4,000 rpm is a more important threshold (for me) than how the vehicle is driven during that period. They are two separate points.

Anyway, 'nuff said. It's a great subtle point you bring up. I hope you get what I'm trying so inadequately to say.

With regard to engines, I'm more of the belief that engines will either be put together with the right characteristics of fit and finish or not. In many years past, the term "blueprinted" was common amongst racers. In my youth, I worked in a race engine shop as a machinist. We would strive to achieve what vehicle manufacturers do better day in and day out today. It's all because of the more precise machining technology used throughout the automotive manufacturing industry. No manufacturer uses those old planers and shapers that the smallblock and big block chevy was originally made on. But, even those old "blueprinted" racing dinosaurs would get a short break-in for the cams and hit the track. A bearing is either right or not. If there's metal to metal contact in a rod or main bearing, it's likely not going to go the distance. Fortunately, that condition is seldom seen today.

With regard to rpm, any limitation during break-in should be about piston velocity, or more specifically, about the ring/bore velocity. That's a function of the stroke length x the rpm. Small engines have lower piston velocities.

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[LSJKU]

With regard to engines, I'm more of the belief that engines will either be put together with the right characteristics of fit and finish or not. In many years past, the term "blueprinted" was common amongst racers. In my youth, I worked in a race engine shop as a machinist. We would strive to achieve what vehicle manufacturers do better day in and day out today. It's all because of the more precise machining technology used throughout the automotive manufacturing industry. No manufacturer uses those old planers and shapers that the smallblock and big block chevy was originally made on. But, even those old "blueprinted" racing dinosaurs would get a short break-in for the cams and hit the track. A bearing is either right or not. If there's metal to metal contact in a rod or main bearing, it's likely not going to go the distance. Fortunately, that condition is seldom seen today.

With regard to rpm, any limitation during break-in should be about piston velocity, or more specifically, about the ring/bore velocity. That's a function of the stroke length x the rpm. Small engines have lower piston velocities.

Yes sir, understood and fully agree. With respect to piston velocities, you are spot on. I just thought it was more easily conveyed to the non-techie as a general rpm term. But you are absolutely correct.

I come from the old school days myself. I didn't do automotive machining but as a young amateur, I did build a few engines. And a "balanced and blueprinted" engine was the gold standard. Anybody serious about performance was doing it back then. Shaving heads and porting & polishing too.

In 1983 bought an AMC General 401 out of a '71 Matador for $50 (whole car), had it "B&B'd" when I rebuilt it, and tucked it and a T700 in my first Jeep, a '74 CJ5. Why? Because I could. Everyone I hung with was doing it, I was stupid young and had the money. Would I do it again today? Probably not. But those days are where my love of V8s in Jeeps originated. Cubic inches was the basic answer to most ills back then. And that was not a bad thing.

 

[WannFly]

I dont care what Mopar on anyone says, its my new Jeep and I am farting in it all I want from day 0

 

[roaniecowpony]

I dont care what Mopar on anyone says, its my new Jeep and I am farting in it all I want from day 0

Truth. I farted in someone else's jeep.

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