Valve Stem Seals

[ihc1470]

Explained: Why Diesel engines need a throttle body & throttle plate

Explained: Why Diesel engines need a throttle body & throttle plate

www.team-bhp.com

But...what you are explaining in detail is air movement up to the intake valve and not in the cylinder... and I am referring to air movement after the intake valve on a NA older diesel.

I am not saying that there is any significant vacuum in the intake manifold other than what you pointed out from air filter restriction.


On my point...

Since the swept volume of a diesel cylinder is...lets say 'X'...when the piston is at the bottom of its stroke...and the speed of the piston is 'X' when it is moving in the downward direction...and the intake valve opening is many times smaller than the swept volume of the whole cylinder...I am talking NA here...not forced induction...then the only way the cylinder can fill is by the piston creating a vacuum in the cylinder.

I believe you are talking about MANIFOLD vacuum...and I am talking about the dynamics of CYLINDER filling...

Interesting points. Trying to understand your logic a bit better. Do we both agree that a vacuum is created on earth because there is a restriction in air flow? If we do agree on that then I am having a hard time following how you can produce vacuum going past an open intake valve. At least anything that could be measured. Air turbulence yes vacuum I do not see.

Take a cylinder and put a piston in it starting with the piston at one end of the cylinder and then move the piston to the other end of the cylinder and do it so that it takes at least 5 minutes for the travel to happen, also the cylinder is open to atmospheric pressure at both ends just like a NA diesel is when the intake valve is open. Do you believe that as the piston moves that the air will not fill the cylinder as the piston moves away? There would be no vacuum created at the speed I moved the piston yet the cylinder will still fill with air will it not?

Remember that there is 14.7 pounds pushing down on everything at sea level at all times. When you move that piston it is that pressure that fills the cylinder. If you think about it that is also the reason when you go up to 10000 feet the engine is producing less power as there is less pressure to fill the cylinder resulting in less air to support combustion. Nothing else would have changed on the engine. That is the advantage of the Turbo, it will pack the cylinder with air as the boost is higher than atmospheric pressure.

Maybe the best example though is our body. When our diaphragm moves down air enters our lungs and there is no vacuum involved. It is that 14.7 pounds at work. When our diaphragm moves up the used air is expelled. Very much like an internal combustion engine.

 

[hacked89]

That's what I've contemplated doing. So long as the guide-valve clearance is correct, it will be minimal. These engines seem to chew through guides as is, not sure if you could over lube them. This whole topic has me wondering why the idi's do go through guides as bad as they do. Are the rockers sideloading the valves in some way? Would roller rockers fix this? Or is the solution bronze guides and no seals?

We ran no seals on the race engines. I can say right now the amount of smoke produced at startup was minimal. Unless the engine design submerges the springs in oil, the only time I really see oil consumption past guides is because of loose guides as much as it is failed seals.

Agreed - I’ve done an IDI no exhaust seals and it was no concern. Also have similar thoughts to you on the guides but I don’t have a good answer currently.

I can comment on the vacuum discussion but enjoying from the sidelines IHC and XOL

 

[IDIBRONCO]

This also is reminding me of something my Dad told me about him having an argument with a science teacher...he said that...when you draw water through a straw out of a glass...the water moved through the straw by creating a partial vacuum...the science teacher said that the water moved by atmospheric pressure.

I would have to side with your dad on this one although they're probably both right to a degree.

Would roller rockers fix this?

Ask Idiot. I believe that he has used roller rockers on IDIs before.

Or is the solution bronze guides and no seals?

I don't know about the no seals part, but bronze liners are the solution.

 

[Kevin 007]

Installing comp 910's for the first time on a turboed 6.9. And since the umbrella seals on the exhaust don't fit right with the 910s, I will install them without seals on the exhaust side as I don't want to install the positive seals on the exhaust, in fear of accelerated guide wear.