Hydraulic tappets?

Can you fit them to older engines? Is the oil pump beefier and the oil-ways the same?

--Steve

Bad news for any aircooled engine....

I have refused since 1997 to build any hydro engine.

The quiet running almost lets you hear the "tick tock" of the time bomb that is sitting right inside your valve cover.....

I'm adding an article to my website about them that will be available as soon as all the changes are made to the site. IOts 11 pages long so far and I'm 3/4 done with it.

They have ZERO mechanical benefits.

Jake Raby wrote: (with regard to hydraulic cam followers...)

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Like the Corvair? Or the Type IV? :-)

The truth is that juicers are smart... if your goal is long-term reliability. That's why they've been standard equipment in all certified light plane engines since 1937... and were used in big engines as far back as the 1920's.

The reason hydraulic cam followers are used in all modern engines is because they effectively adjust their lash each time they are actuated. That guarantees better long-term performance and reduced fuel consumption to say nothing of reduced maintenance cost.

My dad was an aircraft mechanic. I was working on horizontally opposed air-cooled Lycomings, Franklyns and Continentals years before I even saw my first Volkswagen. I was surprised to find it used solid lifters but the German mechanics I worked with explained that their use would have exceeded the targeted thousand Mark selling price of the original People's Car.

Bottom line is that hydraulic cam-followers have been standard equipment in air cooled engines for more than eighty years and for a host of good reasons.

Lots of VW mechanics are convinced juicers don't work because they got suckered by those 'drop-in' juicers from CB Performance, which simply did not work. The VW engine wasn't designed to use juicers; it does not provide enough oil to the right-hand half of the crankcase to allow proper actuation of the lifters on each end of that oil gallery. But Volkswagen offered hydraulic lifters in some of their industrial engines as far back as the late 1950's. To make them work they opened up a second supply channel to the right-hand half of the crankcase.

Stock, ALL of the oil to the right-hand side of the engine gets there by that tiny channel behind the #2 cam bearing. For juicers, VW opened up a second channel behind #3 bearing as well... a modification which racers immediately adopted since it solved the galling problem with the rocker shaft on that side of the engine.

But it isn't just providing enough oil that makes juicers work. Because of the incredibly small clearances in an hydraulic lifter (ten times smaller than the typical bearing clearnance) you also have to ensure they are provided with CLEAN oil. And that means an oil filter... or changing your oil every 25 hours of use (as with the early airplane engines).

VW de Mexico came up with an entirely new casting in which the tappet bores were thick enough to allow use of the proven Type IV lifters. And they provided a full-flow oil filtration system to go with it. This has proven to be the most reliable Type I ever built. (I live near San Diego. A lot of VW de Mexico stuff leaks across the border :-)

No mystery to any of this. And no secrets, either. Anyone reading this can prove all of the above for themselves by simply taken apart a few engines. Or reading the manuals. (Having forty years experience helps too :-)

-Bob Hoover

You best qualify that as _new_ manuals and frequent review of the literature. If we stuck to the original ACVW specifications, manuals and designs we could probably get a tax-empt status as a religious organization - it is that irrational to believe the ACVW was almost correct from the start.