Didn't track order of valve lifters

Is it just time consuming because of the number of valves involved, or is the feeler gauge access really tight? I remember doing this with a Honda CBR engine, which used shims on the buckets.

 

what is "valve lash"?

 

Valve lash is a small gap between the rocker arm and the valve stem.
As the engine heats up the gap gets tighter due to expansion of valve train parts.

 

but i thought this engine doesn't use rocker arms. my cams are pushing directly against the valve lifters, which sit on top of the valve stems.

 

Sorry, I'm not a V6 guy, I'm old school rocker arm guy lol. I would guess your valve lash is the gap between the lifter and the valve stem. Surely someone that knows will chime in.

 

Same idea. It's a gap that allows for expansion. Too tight, valves don't close correctly, improper running and damage. Too loose, it will be very noisy, valves won't open properly, improper running and damage.

It's important to get it right.

If you watch folks in the pits with performance motors, valve adjustments are a constant ritual. On sedate street vehicles that have solid lifters, it's a mileage based maintenance item. One of the reasons hydraulic lifters are much more common, as this is not required.

 

so I'm still struggling to understand the concept. is this correct: different valve stem tips have different distances between them and their cams, which necessitates differently size valve lifters ?

 

Sort of. The lash adjuster is the 'connection' between the cam and valve. Tolerances, while close, are not perfect. So the lash adjuster is what 'adjusts' the tolerance to a finer, more accurate level. The 'lash' or gap, is what allows expansion to work and not bind, as mentioned earlier.

This article might be helpful to you. It does a fair job of explaining various configurations. http://www.enginebuildermag.com/2010/07/the-liftercam-relationship/

In an OHC application, technically the term 'lifter' is incorrect. It's really a lash adjuster, either hydraulic or solid in nature. The adjustment of the lash (gap) is achieved in various ways, depending on the design.

In the last little high rev motors I tinkered with, the first generation had hydraulic lash adjusters, so 'valve adjustments' were not required. The 2nd generation had solid lash adjusters, but they were mounted in a 'bucket', and various sized shims were used to adjust the lash. While lots of shim sizes were often needed to get the right combination, to me it was easier than this system of multiple sized adjusters.

Point is, to get your situation corrected, it will take a good bit of time & patience along with some basic measuring tools & math skills. Experience would be quite helpful, although the mechanically adept could probably get it done correctly. But the complexity is why several of us have suggested letting a machine shop sort it out for you.

I'm assuming since you mentioned head gasket earlier you'll be having the head checked for trueness, and corrected as needed. If one needs correction, the other should be done to match. Many folks have valve jobs done at the same time, clean things up, improve performance a bit, etc. So, if you're that far apart, letting them reassemble will just take longer since the adjusters are out of order.

Or you could just buy a set of already refreshed heads and bolt them on, as mentioned earlier. You might be surprised how little difference there is in cost. Worth asking about from someplace like http://www.cylinder-heads.com/

 

so are you saying different lifters have different lash adjustments to correspond to different gaps between cams and valve stems? do they get that way over time or are they manufactured that way? if they are manufactured that way, why didn't they imprint the measure of the lash somewhere on the lifter to know which one should go where ?

 

Yes, manufactured that way. The measurement of the bucket shim is printed inside the bucket on the flat surface.

 

so in that case, between the markings on the lifters and some diagram of the valve layout in the head i should have all the necessary info to assemble them back together and it shouldn't matter if i put each exactly where it was before as long as the numbers are matching ?

 

The numbers indicate the thickness of the shim on the bucket, it will matter which goes where depending on the lash of each valve.

 

Isn't the lash of each valve constant ? if so, it should be in the Toyota tech specs, no ? i am trying to understand why i need to do the measuring. is it because the lash actually varies with wear so it needs to be recalibrated over time ?

don't get me wrong, i'm not arguing measuring is needed, i'm just trying to make sense out of it all.

 

The lash varies between valve, but as long as it's within specs it's fine. You can try putting them all in, torquing the camshafts down, going through the measurement procedure, note which is within spec, switch the others, remeasure, rinse and repeat until all are within spec. I honestly don't know of another way to do it, I kept track of mine when I rebuilt my engine. A machine shop would probably have to do the same, unless they happened to have compatible buckets on hand to try.

 

can this lash measuring be done with a regular feeler gauge (straight) or should i get the bent (offset) ones that are marketed as "valve feeler gauges" ?

 

Any gauge within the thickness required will work, although I used the angled ones, it was easier.

 

I think the proper term is tappet

 

Tappet is just an alternate term for lifter or lash adjuster. On an OHC this 'part' isn't lifting a rocker arm, thus it's not a lifter. On rocker arm motors, the lifters (or tappets) can be hydraulic or solid, roller or flat.

On vintage stuff like 6 cyl Chevys of the 50s, before hydraulics (yes, solids are the older technology) if you could not hear a slight bit of valve noise, there was great risk they were too tight and on the edge of causing real issues. If they were too noisy, well, they needed adjusting as well. So while it may sound (pun intended) silly, a trained ear was a modestly accurate diagnostic tool, giving you a hint if it was time for a valve adjustment.

Read the article I linked you to carefully and it will help resolve some terminology. It does seem confusing until you go through it a few times.

 

Not too tight to measure. Just very time consuming, due to all of the valve buckets being mixed up. Normally you will just need to measure and then change the ones that are out of specification. He needs to reassemble, measure and figure what he needs for All the valves. Disassemble then reassemble again installing the correct size buckets onto the correct valves.

 

1.) No the valve lash is not constant enough for setting the lash or gap between the Cam Lobe and the top of the bucket. There are too many variances involved Valve length, Valve Seat position in the head, Head machining tolerances, differences in the valve spring retainers etc ... A build up of tolerances from all of these individual parts can cause issues. That is why each valve is all measured and set separately.

2.) Yes it does indeed vary with wear. It should be checked and any that are out of specification adjusted by replacing the bucket with the required size. I have been driving Toyota's a long time and have never had to have the valves adjusted. I think it is listed in the Maintenance Schedule, but I have not checked.