Solid Lifter Valve Lash Stable for Life of Engine?

[SubLGT]

That seems to be what Subaru claims for the valvetrain in my engine (2.5L DOHC turbo). There is no scheduled check of valve clearances in the maintenance schedule. Checking the valve lash in this engine is not easy (very limited working space), and adjusting valve lash requires camshaft removal and lifter replacement (shims are not used). It is not difficult to find numerous online reports of burnt exhaust valves in Subaru turbo motors, some as early as 95,000 miles.

What other manufacturers of solid lifter engines do not have a requirement in the maintenance schedule for checking valve lash? I know Honda does not fall into that category with their SOHC V6 engine, as they require a check of valve lash at 105,000 miles. (A long time ago, when I owned an air cooled VW, I believe I had to check the valve lash every 3000 miles)

Is Subaru alone in their belief that a solid lifter valvetrain can be maintenance free?

 

[fdcg27]

From your description of what would be involved in correcting clearances in this Subie's valves, I can understand how Subaru would want you to believe that no checks are needed.
Too tight exhaust valves that cannot fully close and exchange heat into their seats will burn in short order.
This seems like a bad design and you have to wonder why Subaru didn't just use hydraulic lifters.

 

[bdcardinal]

My mom's 2014 Fusion with a 2.0L Ecoboost has that setup. There are multiple lifters listed and when you replace a head you have to measure and install the proper ones for clearance. There is no interval for checking or resetting lash.

 

[CT8]

Although having owned Motorcycles and Toyotas that need shims over the cam or under the cam bucket I prefer hydraulic adjusters.

 

[Syntheticuser]

My Focus has mechanical setup bucket shim setup in the Zetec. I have never adjusted them. I have never seen a recommendation on the adjustment either. 287k miles and runs great. I asked a few mechanics in the area and they said they don't fall out of specs very often. I won't do them unless it starts given me problems or someone can produce recommendations that show me an interval for it.

 

[Trav]

Stable for a long time yes, for the life of the engine possibly but if run hard or modified probably not. Subaru IMO has figured out that the best way to do this job is probably remove the heads and if that's the case call it "for life" because if a valve does burn you need to pull it anyway so you might as well pull both.
Some valve adjusting mechanisms are more stable than others but regardless all will wear at some point, the question is how much.

The bucket mechanism whether it uses shim or not has the least wear and being an aluminum head the valve clearance will grow with engine temp not decrease like an iron head so it should be good to go in theory but it isn't.
The one thing they cant figure into their equation is the exact amount of valve seat recession outside of controlled conditions. Those include anything that could increase combustion chamber temps from the fuel being used, time spent under higher boost pressures and tuning, etc, increased temps increases the chance of seat recession or valve erosion.
Sodium filled stems and hardened seat inserts help to minimize these conditions but with a turbo engine especially there is no way to totally eliminate it.

There are 6 point of wear in this particular mechanism, 4 of them can be minimized with the use of a higher zinc content oil like a Euro oil e.g Mobil 1 0w40has 1100ppm zinc. These points are the cam lobe and bucket face, the valve stem tip and the bucket contact area.
The two you cant really do much about is the seat and valve in the combustion chamber other than not using tuning files and modifying the boost pressure, if you want to play you have to pay and the possibility of burned valves or seats are the price of entry with high pressure turbo's.
Lowering the AFR to 12.7:1 under full boost will help keep chamber temps under control.

 

[Wheel]

Which Subaru engine ? They used to want adjustments at 105,000.

 

[SubLGT]

Originally Posted By: Wheel
Which Subaru engine ? They used to want adjustments at 105,000.


EJ255

 

[SubLGT]

Originally Posted By: Syntheticuser
My Focus has mechanical setup bucket shim setup in the Zetec. I have never adjusted them. I have never seen a recommendation on the adjustment either. 287k miles and runs great...


I'm impressed.

 

[PeterPolyol]

Yes, modern solid bucket lifter arrangements don't generally require maintenance. They are often times paired with lower pressure springs and stray from spec far less than 'solid' rocker arm/finger follower types due to the greater friction surface area and the tendency for the buckets to rotate, further evening the wear pattern. This type is used in later model Ford/Mazda 4 cyls. OTOH Honda is a big proponent of finger followers, a habit from VTEC implementation and mass reduction (for high RPMs). They haven't used bucket lifters since the ZC/D16-DOHC from the late 80s, and not surprisingly they're among the most NVH prone valvetrains (although MultiAir is trying to steal the title). I had a 2.2 Camry once with mechanical buckets and they were not exactly quiet (none of them are) but not one lifter was louder than the other; they all made the same amount of noise which evened the noise into a non-offensive homogenous clatter.

 

[FowVay]

My 2017 Nissan Frontier uses a solid bucket lifter in a cam-over-valve design. If the clearance is out of specification then it will require the camshaft to be removed and different buckets installed (no shims).

There is no requirement for routine checking of valve clearance in the manual. It states that if they become noisy then they should be checked and clearances corrected.

 

[Wheel]

It's gone from my 2009 service manual as a regular check. They only describe the process.

 

[Jetronic]

Originally Posted By: SubLGT
That seems to be what Subaru claims for the valvetrain in my engine (2.5L DOHC turbo). There is no scheduled check of valve clearances in the maintenance schedule. Checking the valve lash in this engine is not easy (very limited working space), and adjusting valve lash requires camshaft removal and lifter replacement (shims are not used). It is not difficult to find numerous online reports of burnt exhaust valves in Subaru turbo motors, some as early as 95,000 miles.

What other manufacturers of solid lifter engines do not have a requirement in the maintenance schedule for checking valve lash? I know Honda does not fall into that category with their SOHC V6 engine, as they require a check of valve lash at 105,000 miles. (A long time ago, when I owned an air cooled VW, I believe I had to check the valve lash every 3000 miles)

Is Subaru alone in their belief that a solid lifter valvetrain can be maintenance free?



Not really. While some manufacturers do ask for a check, a lot of engines live a long lifewithout altering the valve lash ever.