valve lifters/valve clearance adjustment

I had a Honda Hurricane with shim adjustment. The initial service called for them to be checked, which they did. The mechanic said they were "all over the map", he had to change shims on quite a few. Can't remember how many valves there were, being a 4 cylinder, there'd be at least 8.

 

My 03' BMW with an M54 inline six has hydraulic lifters and twin overhead cams. Also turns 8,000rpm with no valve float. The reason they don't in the Prius is a loss of efficiency. You get a tiny bit of cushioning in the valve system with a hydraulic lifter. That comes a the cost of a bit of wasted energy. It's first and foremost engineered to eek out all MPG it can. That it can be a royal pain in the nice person to fix or adjust when things in that area wear, isn't even on their radar.

 

My (very limited) understanding is the hydraulic lifters maintain optimum clearance, , without the need for periodic adjustment, unless they fail somehow, say gum up.

2nd gen Prius had shims, were insanely difficult to adjust, best just left alone whenever possible.

Prior to acquiring our 2010 Prius I had 30 years of Hondas, am familiar with screw and locknut adjustment.

 

You can add to your list the Toyota 2ZR engine, used in the Gen 3 and later Prius and the Prius v. The "where would you put them" question has a clever answer. The 2ZR rockers are below the cams. The cams push the rockers down in the middle. The valve is beneath one end of the rocker. The hydraulic adjuster is beneath the other end, as a fulcrum. The mass of the adjuster, therefore, isn't in motion.

The 1NZ engine, used in the 2nd gen and 1st gen Prius and the Prius c, does not even have shims under the lifters. It's the lifters themselves that are sold in 35 different sizes, and have to be replaced with other sizes to change the adjustment.

 

And access involves cam shaft removal. Can they be snuck out from under the timing chain? I’d hope so.

 

Just to show it's not necessary to be that clever about it, Mazda's 1.6L overhead cam B6 engine back in 1988 had conventional-looking rockers and they just had hydraulic lash adjusters built into the ends where screws and locknuts would otherwise go. So in that design the mass of the adjuster did have to wag up and down, but it apparently just wasn't that much of a problem.

 

Off-topic, but our sons Mazda CX-5 allows owners to swap between 2 sets of tpms equipped wheels without dealership intervention or special tools. Just drive steady for a minute or two, the car recognizes the swap ok.

 

Mazdas weren't that bad, however Mitsubishi used a similar design that had problems with the hydraulic lash adjusters intermittently collapsing. They would sit at idle- tap, tap, tapping away, only to gradually get quieter - for a few minutes. Then back to tapping.

Really, Toyota's cam over bucket/shim design is pretty much bullet proof. Back in the early 90's I used to check valve clearance per factory maintenance schedule but stopped doing it because it was always still in spec.

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Hondas screw adjusters always drifted towards looser in my experience, but slowly.

 

Or cam over bucket. It gets tiring adding reminders that there are no shims.

Not saying there mightn't be other Toyota engines with shims ... just that the 1NZ engines used in Prii don't have them.

 

True enough. There's the shim on the bucket, I think some makes used a bucket on the shim (might be an aftermarket performance mod) , and now there is the one piece (select size) bucket. I never kept track of which is which since I never have to mess with them.

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Hello guys!
I've Yaris 1.5 Hybrid with X1NZ-P92 engine and I've to adjust a valve clearance but I would like to change oryginal "in one pice " lifters for lifters with removalbe shimes like used in old Toyota engines ( e.g 4E-FE, - dimmension 28mm to 23 mm) If someone will be albe to tell me what are the dimmensions of valve lifters in 1.5 liter PRIUS engine? ( I dont want to disassembling camshaft and after looking for proper lifters but I'm sure that they are similar in Yaris and Prius )
THX for any help