07-31-2019, 10:41 PM
Hi Tommy, welcome to the forum and thank you for posting your vc's.
I don't claim to be a mechanic but i like to know "what makes things tick" and have always done my own maintenance on my vehicles so take my advice with some skepticism and if anyone has a better explanation i would like to hear it so we all can learn something and improve ourselves
The impression i get from reading the spreadsheet is that initially when the engine is new the cams and buckets are not " polished in " , they are ground and have to achieve their high polish over time as the engine runs in and they rotate in their position as can be seen from the markings on the top of the buckets, who are truly worn round, this is done on purpose, all cams are positioned eccentric so the area of "wear" is as big as possible to prolong the life of the engine and to extend the valve adjustments increments.
For this reason it is important that the buckets do not get mixed up and all end up in their respective seats and the shims are placed with the text facing up on top of the valves where they have the biggest mechanical support area and have lubrication applied when re-inserted in their position
These area's are a lot bigger than the original screw adjustable tappets from the old style and retain an oil film much better.
During this time the valves also run in and settle on the seats, they do not rotate and are always under spring tension.
So in the "settling period" anything can happen, the clearance can get bigger or smaller depending on how good the technician at the time installed the valve clearance and if there are deposits that settle on the seat surface and decrease the vc, this is picked up at the first vc check.
The trend is for them to increase the vc so the shims are replaced with bigger sizes ( best are done with 0.025 mm. shim intervals ) but there is the odd one that gets smaller, so it depends.
The valve system is designed to have long vc intervals and slowly increase as the valves wear the seats down over time.
Generally small vc is bad because the valve can fail to close, not cool enough and consequently burn ( melt ) when the engine heats up, but a loose valve is not such a bad thing although it wears faster and is noisier, it still cools enough as the seat transfers the heat from the exhaust gas when it is closed.
I don't claim to be a mechanic but i like to know "what makes things tick" and have always done my own maintenance on my vehicles so take my advice with some skepticism and if anyone has a better explanation i would like to hear it so we all can learn something and improve ourselves
The impression i get from reading the spreadsheet is that initially when the engine is new the cams and buckets are not " polished in " , they are ground and have to achieve their high polish over time as the engine runs in and they rotate in their position as can be seen from the markings on the top of the buckets, who are truly worn round, this is done on purpose, all cams are positioned eccentric so the area of "wear" is as big as possible to prolong the life of the engine and to extend the valve adjustments increments.
For this reason it is important that the buckets do not get mixed up and all end up in their respective seats and the shims are placed with the text facing up on top of the valves where they have the biggest mechanical support area and have lubrication applied when re-inserted in their position
These area's are a lot bigger than the original screw adjustable tappets from the old style and retain an oil film much better.
During this time the valves also run in and settle on the seats, they do not rotate and are always under spring tension.
So in the "settling period" anything can happen, the clearance can get bigger or smaller depending on how good the technician at the time installed the valve clearance and if there are deposits that settle on the seat surface and decrease the vc, this is picked up at the first vc check.
The trend is for them to increase the vc so the shims are replaced with bigger sizes ( best are done with 0.025 mm. shim intervals ) but there is the odd one that gets smaller, so it depends.
The valve system is designed to have long vc intervals and slowly increase as the valves wear the seats down over time.
Generally small vc is bad because the valve can fail to close, not cool enough and consequently burn ( melt ) when the engine heats up, but a loose valve is not such a bad thing although it wears faster and is noisier, it still cools enough as the seat transfers the heat from the exhaust gas when it is closed.