Hydraulic lifters on Toyota engines??????

It does seem kind of odd since hydralic lifters have been around since the 1950's. I'm sure there must be reasons other than lack of engineering or saving a few dollars per vehicle.

I'm sure one of the tech experts will know the reason(s).

I don't know either, but both my 1990 Truck and my 1995 4-Runner always sound to me like the valve lash is out of adjustment.

I remember working on my girlfriends 1967 Datsun 2000 Roadster and after having the heads worked on, the valve lash had to be adjusted. Was pretty easy on that engine. I guess it isn't very easy on the V-6 Toyota engines.

Kirk

In traditional overhead valve push rod engines, hydraulic lifters make sense because of the several time/temperature variables in the valve train. It is a long path from the cam shaft in the block, thru the lifters, push rods, and rocker arms, and then finally to the valves in the head. A significant influence on that path length is the head gasket thickness change over time. So in this instance the hydraulic lifters can accommodate those changes. And with only two valves per cylinder, the economics can still be reasonable.

But in modern multi valve, overhead cam designs, the trade off changes. Some older SOHC engines, still with only two valves per cylinder, have integrated the hydraulic lifters into the rocker arms. But at four valves per cylinder, and without the intervening head gasket variable, it starts to make sense to go totally mechanical.

The V8's in the LC, Tundra, and Sequoia are an example. Each cam shaft (DOHC - there are 4, two in each head) actuates the valves directly with only a simple solid lifter/shim set interposed between each cam lobe and the valve stem. The shim is chosen at build (or rebuild) and should be correct until the next rebuild. This of course assumes that the valve and valve seat do not wear appreciably, and that the materials and heat treating of the cam shaft and lifters are properly chosen. There aren't very many dimensional variables left in this design.

Also don't forget also that hydraulic lifter engines are not without their problems. When that intermittent tick-tick-tick starts bugging you, the only choice is usually a major maintenance event. Hydraulic lifters can, and often do, get sticky with age and heat, and it's no mean feat to keep them working smoothly.

Dick Ballard snipped-for-privacy@att.net

This has been interesting reading. Does my 94 4Runner's V6 with 158,000 miles on it need its valves adjusted?

Bill

I would imagine that without a roller-type lifter, wear would be inevitable. Even with a roller lifter, the bearings must wear over time causing a change in valve lash...

I have a couple of toyota engines with over 300,000 miles on them and haven't had to adjust the valves yet. If the valve train is getting noisey then the valve seats may be worn, and you would then have more to look at than an adjustment. IMHO, you don't need to mess with the valve train unless it is making serious noise.

I like the way the valves adjust on my 22 4cyl engines, with a screwdriver and feeler gauge. I hate the way my 90 4Runner V6 valves adjust, changing out shims.....what a pain.

opinions will vary, jk

Explain this lack of engineering ?

I don't understand your question, well, acutally a request with a question mark after it. I didn't say it was a lack of engineering, I said there must be a reason OTHER THAN a lack of engineering...

Now one for you; Explain air? :>))

FWIW, Toyota fuel injectors sometimes tap, and they can sound a lot like valves tapping.

opinions will vary, jk