LS3 and L99 Cutaways

[Mr Twisty]

Welcome...I want that LS3 poster! Got the L99 and this one at Indy.

[Robert91RS]

Originally Posted by o2camaross

look at the cam gear on the L99. WAY different, i wonder what it does? maybe some sort of clutch the advances or retards the cam. I think ill call it Variable Valve timing and patent it

LOL. refer here http://www.camaro5.com/forums/showthread.php?t=7057

[Grape Ape]

Originally Posted by Robert91RS

That appears to be the spring in the hydraulic roller lifter.

They are needed to force the lower portion of the follower down onto the base circle of the cam when it is in deact mode so as to be ready to reactive and probably keep the pushrod tip on the rocker. Without them the lifter might stay up where the cam lobe pushes it.

Originally Posted by Robert91RS

I bet it's so that if the afm gets stuck and holds a valve open it won't make contact with the piston. I know you don't want to miss oil changes with the afm or use the wrong oil.

The AFM deact lifter could fail in a way that would cause it not to reactivate (and the valve not to open) or it could fail to deactivate (and act as a normal lifter). But I don’t see how it could cause the valve to stay open, at least not outside of a bizarre failure that would also apply to a non-AFM engine.

I think that the cuts are an illustrator error since the location of the cuts doesn’t make any sense for that head design.

I’m reminded of an infamous H&K pistol ad that showed the rounds loaded into the magazine backwards. The people who do this kind of work are not car guys or gun guys, they are guys who went to art school and somehow managed to learn how to make things that look like things. But if you don’t know what you are looking at you are libel to goof a detail every once in a while.

Or maybe they are just worried about valve float.

[Robert91RS]

Originally Posted by Grape Ape

They are needed to force the lower portion of the follower down onto the base circle of the cam when it is in deact mode so as to be ready to reactive and probably keep the pushrod tip on the rocker. Without them the lifter might stay up where the cam lobe pushes it.



The AFM deact lifter could fail in a way that would cause it not to reactivate (and the valve not to open) or it could fail to deactivate (and act as a normal lifter). But I don’t see how it could cause the valve to stay open, at least not outside of a bizarre failure that would also apply to a non-AFM engine.

I think that the cuts are an illustrator error since the location of the cuts doesn’t make any sense for that head design.

I’m reminded of an infamous H&K pistol ad that showed the rounds loaded into the magazine backwards. The people who do this kind of work are not car guys or gun guys, they are guys who went to art school and somehow managed to learn how to make things that look like things. But if you don’t know what you are looking at you are libel to goof a detail every once in a while.

Or maybe they are just worried about valve float.

Haha I will have to look for that H&K add. I didn't think about there locations.

[zebra]

[Camaro68]

Originally Posted by MisterCamaro69

Welcome...I want that LS3 poster! Got the L99 and this one at Indy.

that's awesome that you got those signitures on the DI Engine poster

[glazr69]

Originally Posted by Grape Ape

They are needed to force the lower portion of the follower down onto the base circle of the cam when it is in deact mode so as to be ready to reactive and probably keep the pushrod tip on the rocker. Without them the lifter might stay up where the cam lobe pushes it.



The AFM deact lifter could fail in a way that would cause it not to reactivate (and the valve not to open) or it could fail to deactivate (and act as a normal lifter). But I don’t see how it could cause the valve to stay open, at least not outside of a bizarre failure that would also apply to a non-AFM engine.

I think that the cuts are an illustrator error since the location of the cuts doesn’t make any sense for that head design.

I’m reminded of an infamous H&K pistol ad that showed the rounds loaded into the magazine backwards. The people who do this kind of work are not car guys or gun guys, they are guys who went to art school and somehow managed to learn how to make things that look like things. But if you don’t know what you are looking at you are libel to goof a detail every once in a while.

Or maybe they are just worried about valve float.

When deactivating cylinders, the valves on the inactive ones are held open. This helps resuce mechanical losses, as you dont want to be compressing air on the compression strokes, and dont want to be creating a vaccum on what would be the combustion stroke.

[Mr. Wyndham]

Originally Posted by glazr69

When deactivating cylinders, the valves on the inactive ones are held open. This helps resuce mechanical losses, as you dont want to be compressing air on the compression strokes, and dont want to be creating a vaccum on what would be the combustion stroke.

Not in GM's version. They keep the valves closed, so the air being compressed acts like a spring during piston travel to BDC. Supposedly, Chrysler's 5.7 V8 acts the way you described. And it seems to work better, because they're getting another mpg more out of the system.

[Robert91RS]

Just an update now that the L99 and LS3 are both in the GM catalog now. For grinns I check the pistons and they are using different numbers. The crankshaft castings are also different. These motors may be a little more unique than we thought.

[CamaroSpike23]

Originally Posted by Robert91RS

Just an update now that the L99 and LS3 are both in the GM catalog now. For grinns I check the pistons and they are using different numbers. The crankshaft castings are also different. These motors may be a little more unique than we thought.

the pistons are different. the L99 has dished pistons

and I would imagine that the L99 crankshaft is slightly lighter to aid in the fact that AFM is having the engine turn over and move the car with only 4 cyls. just a thought tho.

[fad1]

I may just stick with the L99 auto in my SS and just be happy with it. I can try to improve fuel economy and HP by CAI and some nice Exhausts.

[Andro]

Nice Find