Bucket lifters,

[ARCOgraphite]

I see the bucket tappet as a "CHEAP" engine design. And NONE of my last 5 cars are lasting on this "wonderful" SM oil. Piston slap, high oil usage on all of them and cams going on the OHC bucket tappet ones. My yaris will be next to go at 26K - trying hard to save it, but its giving bad indications this week. I couldnt buy any John Deere SL 10w30 lawnmower oil at Home depot a couple hours ago - its all sold out. Fess up! Who here stashed it all!?

 

[Doug Hillary]

Hi,
there are many variations in the design of valve train components. Rollers are not always the best deal - they are great in certain applications (Series 60 Detroits (ceramic) for example) and buckets do work best in others like some Euro engines (some Porsche engine families)

Rollers can create traction problems with some lubricants (or vice versa) and whilst rollers are generally reliable they do have problems (like pin failures and etc)

It is a case of the engine designer having a Portfolio of possibilites and using the best one for the task - performance, durability, package size and cost/benefit being just some of the prime guidelines

Personally I see the wisdom in both

 

[cven]

How about we get rid of all the bad stuff?

http://www.ducatidesmo.com/


In the motorcycle world buckets work at very high rpm and from what I've seen on my bikes and others they hold up pretty good. If you keep them in spec problems are rare but they do happen.

 

[ARCOgraphite]

Bike oil is much stouter than pass car oil, I wouldnt wan to adjust a desmo on a pass car - plus no need for desmo at low engine speed.

 

[OVERKILL]

Originally Posted By: Doug Hillary
Hi,
there are many variations in the design of valve train components. Rollers are not always the best deal - they are great in certain applications (Series 60 Detroits (ceramic) for example) and buckets do work best in others like some Euro engines (some Porsche engine families)

Rollers can create traction problems with some lubricants (or vice versa) and whilst rollers are generally reliable they do have problems (like pin failures and etc)

It is a case of the engine designer having a Portfolio of possibilites and using the best one for the task - performance, durability, package size and cost/benefit being just some of the prime guidelines

Personally I see the wisdom in both



That is a different perspective on things, thank you Doug. I guess I had always figured that buckets were simply inferior, yet for something exotic as a Porsche... there has to be a reason!

Do you have any diagrams of how the Porsche setup is configured?

I am only familar with the general layout of a few of the Japanese styles and obviously that of Ford, which is roller. This is of course my reference point.....

I could see the advantage of a bucket setup being a lighter valvetrain.... Which means one could spec lighter springs. Though with the Ford Modular engines, it appears as though the roller setup has proven to be fantastic for durability....

And unlike setups from Honda, it requires zero maintenance.

Like running solid lifters, of both the roller and flat variety, I imagine there is a solid REASON for buckets to be used in a performance engine. I simply don't see the logic (other than cost) for them to be used on a "normal" car, where a hydraulic-lashed roller setup (like the one Ford uses) would eliminate having to open the valve cover.... pretty much ever.

In case you are unfamiliar with the Ford SOHC setup:

The rocker/bucket has a recess that fits over the top of the valve. In the middle there is a roller. Lash is taken up via a hydraulic lash adjuster which looks like a tiny lifter and is situated on the the opposite end and subsequently acts as the far mounting point. The cam sits on top of this setup and acts upon the rocker/bucket assembly via the roller.

It is pretty basic, and likely why it is very problem-free.

What has been your experience with rollers "skating" as you've mentioned?

Your knowledge always makes me curious

 

[Doug Hillary]

Hi,
OVERK1LL - I will send you some data on the Porsche buckets - some in use since the 1960s and those used in the M96 engine family. These require no maintenance is operation. Switchable buckets (hydraulic/mechanical) have been used since the 1990s with the German Company INA being a trailblazer in many types of valve train components

As many of us will recall, bucket design was often a soft/discrete way of rev limiting an engine - before ECMs arrived of course

Please send me a PM with your email address

Regards

 

[OVERKILL]

Done. Thanks Doug!

-Chris

 

[ARCOgraphite]

How do you rev limit an engine with a bucket design? Not familiar with that. Valve float will rev limit an engine but not a good practice on interference head designs. The only issue I see with inverted buckets is the large/heavy cam base circle and the high contact point velocity seen by the tappet - other than the adjustability issues. Seconday issue would be windage in the oil bath around the buckets and a possible HD wedge effect with highly viscous lubricants. When you add a fulcrum with mechanical advantage to the design you can utilise a smaller cam effective base radius and add lash takup easily to the lower class lever geometry.

 

[twigdog]

Pablo, you out there? Do I remember correctly seeing you running something like 20,000 mile changes in an old Red Block? What kind of oil were you running with what results? I seem to remember them as good.

 

[Doug Hillary]

Hi,
ARCOgraphite - By design and operation that initiates valve float and etc. This is a similar "soft" approach to using restrictive intake and exhaust systems as well. Many engine families in this era were very "lethargic" beyond about 3.5k - 4k rpm - by such design!

The World was alive in the 1950s and 1960s with solid lifter alternatives, freeflow exhausts, tuned exhaust manifolds, specialised intake manifolds and advanced carburettor setups. A tuned exhaust on a Type 1 or 3 VW as an example was a real performance enhancer in the era where VWs were the most popular selling car in Australia, some of Europe and all of Scandinavia

At a recent visit to the Nurburgring (and at Philip Island in 2005 - Porsche Historic Factory racer visit) the most experienced Engineers said they spent more time on electronic tuning than worrying about lubricant viscosity and other "parasitic" matters

There are a number of very advanced bucket lifters in use today. They are extremely reliable and functional at approaching 10k rpm and maybe above!