From: Leftie on 24 Jul 2008 09:58
Retired VIP wrote:
> On Wed, 23 Jul 2008 16:26:59 -0400, "C. E. White"
> <cewhite3(a)mindspring.com> wrote:
>> "Steve" <no(a)spam.thanks> wrote in message
>>> Shims-in-a-bucket cam followers for valve adjustment is positively
>>> stone-age (the last car I had so-equipped was a '78 Plymouth Horizon with
>>> the VW-based SOHC 4). Rocker-tip mounted hydraulic lash adjusters that are
>>> common now don't carry enough mass penalty to worry about and are commonly
>>> used in engines with 7500+ RPM redlines. That said, I never had to adjust
>>> the valves on that VW engine either. Everything else about it sucked, but
>>> the valves never needed adjustment! ;P
>> Numerous modern engines from Toyota and Nissan do not use hydraulic lash
>> adjustment. The most modern Camry V-6 does have hydraulic lash adjusters,
>> the older Camry V-6 and 4 cylinders do not. The engines without hydralic
>> lash adjustment do require routine valve clearance checking (if not actual
>> adjustment). I think this requirment is widely ignored. Interesting, Fords,
>> newest V-6 also does not have hydraulic valve adjustment - I guess they have
>> learned from Toyota.
> I guess I'm just to stupid for my shirt. How is increasing the amount
> of necessary routine maintenance as well as increasing the cost of
> operation a step forward?
There are two problems with hydraulic lifters: they are more
expensive to build and, more to the point for us, they tend to fail long
before the rest of the engine. Who wants to have to spend $1k on new
lifters on a car with 150k miles on it? The shim & bucket type setup
rarely needs adjustment when properly designed (and it is as used by
Toyota and Volvo in their older engines) and it doesn't fail. I've had
two cars and one motorcycle suffer from hydraulic lifter failure. I'd
much rather have the valves adjusted every 5 years or so.
From: Scott Dorsey on 24 Jul 2008 09:15
Leftie <No(a)Thanks.net> wrote:
> There are two problems with hydraulic lifters: they are more
>expensive to build and, more to the point for us, they tend to fail long
>before the rest of the engine. Who wants to have to spend $1k on new
>lifters on a car with 150k miles on it? The shim & bucket type setup
>rarely needs adjustment when properly designed (and it is as used by
>Toyota and Volvo in their older engines) and it doesn't fail. I've had
>two cars and one motorcycle suffer from hydraulic lifter failure. I'd
>much rather have the valves adjusted every 5 years or so.
The unfortunate problem is that most people don't do proper maintenance on
their vehicles. As a consequence, manufacturers design cars to avoid
the need for that maintenance because, given the poor treatment of the
average owner, the car will last longer as a result.
This means hydraulic lifters, but it also means sealed chassis components
that don't need regular greasing with every oil change but which fail
before 80,000 miles is up. It means "sealed for life" transmissions, where
that life is about half what it should be.
This is what the market demands, and it's what is best for the average car
owner today. Sadly it's not what is best for folks who actually intend on
taking good care of their vehicles, but those people are in a small minority
and probably always have been.
"C'est un Nagra. C'est suisse, et tres, tres precis."
From: Steve on 24 Jul 2008 10:35
> Actually, the reason to go to mechanical lash is not for high speed
> valvetrain control but rather to reduce engine friction. The hydraulic
> lash adjusters exert a significant amount of force on the cam base
> circle, increasing mechanical friction. This IS both measureable and
> does contribute to fuel savings. If you examine the base circle of the
> came you can even see the lobe is narrower and flairs out to a wider
> surface (Ford Zetec).
That would be a lot more palatable explanation if not for two factors:
1) Lash adjusters (unlike hydraulic lifters) are generally located at
the valve-stem end of the follower. They're about the diameter of a
valve stem, not a lifter. Therefore, the plunger inside them is about
the diameter of a valve stem, not order-of 5/8 inch like a lifter.
Taking the oil pressure and multiplying it by the surface area of the
lash adjuster plunger produces a TINY number. When lift begins the
valves in the lash adjuster close and the entrained oil is
incompressible so they don't collapse, but the BASE CIRCLE pressure is
solely due to engine oil pressure multiplied by plunger area, and is
2) With roller followers cam followers, adding base circle pressure
doesn't increase friction much at all. That's one big reason they're
used- far far lower friction than flat lifters from base circle all the
way to full lift. And of course they can follow a lobe profile with a
much sharper ramp rate so that you can get long duration without
> With modern oils and their additive packages, the need for frequent lash
> adjustment is very rare. Most will make it thought the mandatory 100k
> emissions durability requirements with no adjustment.
No argument there, but I still think eliminating auto lash adjusters is
more cost-driven than engineering-driven. And I don't even disagree that
its a good idea to go ahead and save that money IF the engine can run
200k miles without opening the overhead, as we've come to expect from
cars with hydro lifters or hydro lash adjusters.
From: Steve on 24 Jul 2008 10:39
> There are two problems with hydraulic lifters: they are more
> expensive to build and, more to the point for us, they tend to fail long
> before the rest of the engine. Who wants to have to spend $1k on new
> lifters on a car with 150k miles on it?
They FAIL before the rest of the engine? Hardly. Ask any mechanic how
many hydraulic lifters or lash adjusters he's had to replace because the
lifter or adjuster ITSELF was a root cause of a problem in the last 10
years and I'll bet you can count the average answer on 1 hand, and if
you probe further you'll find that those were typically in badly
neglected sludged-up engines.
From: Steve on 24 Jul 2008 10:41
Scott Dorsey wrote:
> This means hydraulic lifters, but it also means sealed chassis components
> that don't need regular greasing with every oil change but which fail
> before 80,000 miles is up. It means "sealed for life" transmissions, where
> that life is about half what it should be.
Here here! Eliminating the dipstick on automatic transmissions has to
be the single most unnecessarily STUPID thing car makers have done in
the last 50 years. Maybe since the dawn of the automobile.