The Ford Barn - View Single Post - What is Engine 'Break-in'??

Dave in MN · 03-06-2021, 07:18 PM

Later....
I have a full schedule today, breaking down three engines and breaking in one!

Now it's later...And the engine is through with the "break-in"

"Dave, I do like your thinking regarding snapping the throttle closed to induce oil movement however I am unsure if it will work that way. Work with me to establish how this works. If the piston is at TDC, the oil that is on the cylinder walls is typically below the bottom oil ring as slinging it around is always under that control ring."......

Brent, I realize most of the oil on the cylinder wall is below the lowest ring. The assumption you make disregards or is not mentioning the oil deposited between and above the oil control rings and not factoring the machined slots and holes from the interior of the piston into the lowest oil ring groove. Oil is free to move in either direction through these lower ring groove openings. Excess oil removed/scraped from the walls is passed to the inside of the piston and oil from the oil mist in the crankcase is free to enter these areas in the reverse direction as well. The oil around the lowest ring is the oil I am trying to redistribute.

IMO: Blow-by past the top and middle rings will impact the oil within the lower ring assembly. Most often it will move the accumulated oil to the interior of the piston, would be my assessment. Quickly closing off the throttle plate on an engine at operating speed will change or maybe slightly reverse the oil movement around the lower oil ring(s).

My theory it that any change in the cylinder pressure, assuming there is some blow-by, will cause an interruption to the movement of the oil retained in the oil control ring assembly and could deposit some of that oil above the top ring of the assembly when the cylinder is trying to draw in air with the throttle plate closed. Doing so would provide a bit of additional oil to the middle ring and to a lesser degree to the top ring especially if these rings are not fully seated yet. My belief that I am redistributing some oil around and between the middle and top rings and is why I snap the carb closed a couple times early in the running.

My goal in snapping the throttle closed is to slow down the generation of heat being developed between the middle and top ring and the cylinder wall.

I can usually think of two reasons as to why I do something. While doing the "Snap the throttle closed" I am also listening to the engine perform. I am studying the result and listening for any errant sounds. I cannot say I have ever heard any but nonetheless, I am studying the result.

Thanks for your study Brent, it's always interesting.
Good Day,
Dave

03-06-2021, 07:18 PM	#48
Dave in MN Senior Member Join Date: May 2010 Location: Jordan, MN Posts: 1,411	Re: What is Engine 'Break-in'?? Later.... I have a full schedule today, breaking down three engines and breaking in one! Now it's later...And the engine is through with the "break-in" "Dave, I do like your thinking regarding snapping the throttle closed to induce oil movement however I am unsure if it will work that way. Work with me to establish how this works. If the piston is at TDC, the oil that is on the cylinder walls is typically below the bottom oil ring as slinging it around is always under that control ring."...... Brent, I realize most of the oil on the cylinder wall is below the lowest ring. The assumption you make disregards or is not mentioning the oil deposited between and above the oil control rings and not factoring the machined slots and holes from the interior of the piston into the lowest oil ring groove. Oil is free to move in either direction through these lower ring groove openings. Excess oil removed/scraped from the walls is passed to the inside of the piston and oil from the oil mist in the crankcase is free to enter these areas in the reverse direction as well. The oil around the lowest ring is the oil I am trying to redistribute. IMO: Blow-by past the top and middle rings will impact the oil within the lower ring assembly. Most often it will move the accumulated oil to the interior of the piston, would be my assessment. Quickly closing off the throttle plate on an engine at operating speed will change or maybe slightly reverse the oil movement around the lower oil ring(s). My theory it that any change in the cylinder pressure, assuming there is some blow-by, will cause an interruption to the movement of the oil retained in the oil control ring assembly and could deposit some of that oil above the top ring of the assembly when the cylinder is trying to draw in air with the throttle plate closed. Doing so would provide a bit of additional oil to the middle ring and to a lesser degree to the top ring especially if these rings are not fully seated yet. My belief that I am redistributing some oil around and between the middle and top rings and is why I snap the carb closed a couple times early in the running. My goal in snapping the throttle closed is to slow down the generation of heat being developed between the middle and top ring and the cylinder wall. I can usually think of two reasons as to why I do something. While doing the "Snap the throttle closed" I am also listening to the engine perform. I am studying the result and listening for any errant sounds. I cannot say I have ever heard any but nonetheless, I am studying the result. Thanks for your study Brent, it's always interesting. Good Day, Dave Last edited by Dave in MN; 03-11-2021 at 07:20 PM.