Valve clearances and adjustment
 

I am getting close to finishing up a series of jobs that started with the knock sensor and became much bigger. In addition to the knock sensor, I replaced the timing belt, did a tune-up (spark plugs and wires, pcv valve, cap and rotor), radiator, and more.

Today, I decided to check valve clearances (on the advice of Scope103, and my own curiosity). I figured why not with the plenum off. Might as well.

Here were my measurements in mm, with those out of spec in red font:

Intake: 0.18-0.28m, Exhaust: 0.22-0.32mm

Cyl 1 -- 0.25 intake, 0.18 exhaust
Cyl 2 -- 0.30 intake, 0.28 exhaust
Cyl 3 -- 0.40 intake, 0.23 exhaust
Cyl 4 -- 0.25 intake, 0.30 exhaust
Cyl 5 -- 0.30 intake, 0.33 exhaust
Cyl 6 -- 0.25 intake, 0.25 exhaust

The tight exhaust valve on cylinder 1 and loose intake valve on cylinder 3 concern me the most. My understanding is that the tight exhaust valve could be the most problematic, since it could burn out.

Is a valve adjustment a job a novice like me should do, or is it best left to the pros? There is a short video I found making it look rather easy to remove and replace the shims with the right tools ( ). These tools can be found on Amazon for $45.

Advice anyone? I would hate driving around knowing I have the tight exhaust valve. But some people online seem to suggest valve adjustments on the 3vze are only really necessary when you hear 'clacking'. Should I do it? Should I never have checked the clearances in the first place because ignorance is bliss? :laugh:

A little noise is better than no noise.

It is always prudent to hold exhaust valve clearances near maximum.

That video sure makes it look easy, doesn't it! You'll find that the very first one you do will take you 3-5 minutes. The next one, and every one after that, will be just as fast as in the video. Don't get discouraged. (Remember to rotate the "bucket" so the notch for the screwdriver is pointing in the right direction, before you push the bucket down.)

You'll need a micrometer or caliper; this will do fine: https://www.harborfreight.com/6-in-d...ngs-63731.html The tricky part is finding the replacement shims. When I had my heads machined the mechanic had the full set. The next time I adjusted valves, I paid like $20 each (inc. shipping). What you hope to do is mix-and-match. Take the measurement of each current shim you're thinking of replacing, then figure out the thickness shim you want in each location. Remember it's a range; usually the shim you "want" can be any of three different sizes. Can you swap any of them to make it right? Usually, the problem is you don't have enough clearance (the shim is too thick), because with wear the valve sits deeper in the seat. But you've got them going in both directions, so you might get lucky. Even if you're not perfectly lucky, with 5 out of spec you might be able to shuffle what you have and you'll only need to buy, oh, two.

A machine shop with a precision surface grinder can take a few thousandths off any thick one.

Make sure they grind the back and not the cam side.

How do you tell the difference?
New shims look the same on both sides. The shim size is printed on one side, but I've never seen anything that says "always put the marking up" (or down).

Apparently, some valve shims are slightly domed, so using a surface grinder wouldn't work. But not ours.

I refer to a used shim that has bedded with it's cam lobe and will be placed back in its original bucket.

These should only be ground on their backs.

Not best practice to make those already friction mated parts have to re-aquaint themselves a second time.

Thanks guys. I ordered the Schley tools off Amazon. Hope to shuffle the shims around a bit and reduce the cost of new or machined ones. Then hopefully she starts up and runs like a queen :cheers:

Additional question for you guys -- Is it even worth replacing an exhaust shim that is just barely out of spec on the upper end? For instance, the exhaust valve on cylinder five has 0.33 clearance, barely 0.01 mm out of spec. My understanding is that over time this is likely to wear itself into spec. Even if it didn't, I wonder if its effect on performance is negligible.

No, it is not necessary to change number five exhaust clearance.

Agreed; 0.01mm is not a lot. But I'd at least pull it out and measure it. In your shuffling process, you might find a combination that works well and brings that one right into the middle of the range. At least it can't hurt.

Hey guys, I started working on this tonight. I was able to remove a shim (took me a little bit to figure it out, but I got it). I want to switch it with another shim, but this requires turning the engine.. Is it safe to turn the engine when a valve is missing its shim, or do I need to make sure the lobe doesn't hit the valve without it?

Also, how worried should I be about scoring the bucket with the Schley tool? I had one shim get stuck where it wasn't seated in the bucket, compressed against the camshaft lobe. I finally got it seated, but I think it got some minor score marks on the shim, and only barely perceptible on the very outer edges of the bucket where the Schley tool made contact.

Any advice on above comment? I may end up buying new shims one at a time. Shuffling them around would be nice but I don't want to cause damage when rotating the crank on valves without shims.

If I may hijack here, so sloppy exhaust is good. Would intakes be preferred looser as well?

Exhaust clearances tend to tighten up in service because of seat recession and valve stem stretching because exhaust valves operate at continuous red heat.

The looser exhaust clearances are, (within reason) the cooler that valve runs, because it remains seated a bit longer and can transfer a bit more of its heat into the valve seat/head casting.

This promotes longer service life.

Intakes suffer less seat recession and stem stretching because they operate at relatively cool temperatures, so they tend to hold whatever clearances they are adjusted to.

So no, it is not nearly so important that intake clearances are set to max.

Thank you for the input!

3 years later, but I figured maybe it would be good to follow up on this.

I was able to do the valve adjustments successfully. I had to order more shims that I preferred, but in the end, after scrupulous measurements, I got them installed and the truck has been running good ever since (apart from a couple unrelated issues).

One note on the Schley tool in the video above -- it is very useful for doing this job. But I found it more useful to unscrew it into two different parts and only use the main piece to compress the shims. It worked better for me this way.

It's a somewhat intimidating job that many will tell you should only be done by a professional. But I did it, and so maybe can you.