OK to chamfer top piston ring?

[meep]

Originally Posted By: mechtech2
I have worked on a few small old 2 stroke engines that had the head integral to the bore.
The piston went in from the bottom, but the bore was chamfered for this.

BTW, revving an engine loaded or unloaded is about the same.
Why?
Because it is the UNLOADED exhaust stroke that the max load occurs a the rod and bearings.
This is the same loaded or unloaded - it is RPM dependent only.


Mechtech... what you say makes sense... I'm trying to recall where I got my info from... it was either a chrysler publication or a 4wd rag. I believed it to be true since I have had 2 vehicles that have a 4k rev limit in N but a redline limit in gear. Is there another reason they'd instill a lower rev limit in N?

Mike

 

[QuadDriver]

If this were a motorcyle engine you have to do it this way as the piston assembly is pressed on at build time. but I cannot see a car motor clearing the bearings OR the ridge of junk at the bottom of the cylinder. what work does he think he is saving?

 

[Colt45ws]

Originally Posted By: meep
Originally Posted By: mechtech2
I have worked on a few small old 2 stroke engines that had the head integral to the bore.
The piston went in from the bottom, but the bore was chamfered for this.

BTW, revving an engine loaded or unloaded is about the same.
Why?
Because it is the UNLOADED exhaust stroke that the max load occurs a the rod and bearings.
This is the same loaded or unloaded - it is RPM dependent only.


Mechtech... what you say makes sense... I'm trying to recall where I got my info from... it was either a chrysler publication or a 4wd rag. I believed it to be true since I have had 2 vehicles that have a 4k rev limit in N but a redline limit in gear. Is there another reason they'd instill a lower rev limit in N?

Mike

So it isnt at 6grand when people neutral drop it.

 

[punisher]

With some older engines assembling the piston from the block side was normal as some manufacturers didn't trust head gaskets. Need to replace a valve? Drop the crank.

Then you had the crank case by itself, and integral jug/heads (VW with the cylinder and head cast as one unit.

Originally Posted By: mechtech2

BTW, revving an engine loaded or unloaded is about the same.
Why?
Because it is the UNLOADED exhaust stroke that the max load occurs a the rod and bearings.
This is the same loaded or unloaded - it is RPM dependent only.


Don't tell that to anybody at the track. On an engine at WOT the piston still has to pump out the exhaust gas on the exhaust stroke. Think of it as a big gas cushion counterbalancing inertial forces. Worst thing to stress rods is a high RPM/low absolute manifold pressure situation (like downshifting to 2nd gear at 60 mph, or leaving the car in gear at the end of a quarter mile run).

 

[kaboom10]

This is hilarious. Maybe try a halistic mechanic?

 

[mechtech2]

Originally Posted By: punisher
With some older engines assembling the piston from the block side was normal as some manufacturers didn't trust head gaskets. Need to replace a valve? Drop the crank.

Then you had the crank case by itself, and integral jug/heads (VW with the cylinder and head cast as one unit.

Originally Posted By: mechtech2

BTW, revving an engine loaded or unloaded is about the same.
Why?
Because it is the UNLOADED exhaust stroke that the max load occurs a the rod and bearings.
This is the same loaded or unloaded - it is RPM dependent only.


Don't tell that to anybody at the track. On an engine at WOT the piston still has to pump out the exhaust gas on the exhaust stroke. Think of it as a big gas cushion counterbalancing inertial forces. Worst thing to stress rods is a high RPM/low absolute manifold pressure situation (like downshifting to 2nd gear at 60 mph, or leaving the car in gear at the end of a quarter mile run).



Yes, there will be technically more exhaust back pressure - there will be some difference.
That is why I said "ABOUT the same".
But either way, exhaust back pressure compared to cylinder pressure when firing, is insignificant.

As to a lower RPM limit in neutral, it is [like mentioned] because no one can 'neutral drop' into gear, and because there is no reason to rev that high in neutral. Not for testing any component, or to drive any accessory, or any need for power.