Should I get valves adjusted while I’m replacing head gasket?

I’m sending my heads off in a couple days for re-machining and wondering if I should have them adjust the valves while they have it? I have 278K miles on the engine.

Do 3.4s need maintenance adjusting? Would new adjustments put extra pressure on the piston rings? I don’t want to fix something that ain’t broken, but since the heads are already off and the professionals offer the service…I don’t want to miss this opportunity but I also don’t want to add more stress to this high mileage engine.

 

I would absolutely have the valves adjusted. Burnt valves are still a thing with the 3.4l. When I purchased the remanufactered heads for my 3.4l the shop owner told me he likes to check them every 50-60k miles on the 3.4l. Says they usually don't need adjustment that soon but that is what he does. Cracks in the heads near the valve seats, like mine had, are also common on these heads accordingto him. Not sure if tight valves have anything to do with that.
This is a business that specializes in rebuilding Toyota engines, heads, and sells Toyota parts..

 

Thanks for your reply! I am inclined to agree with you.
The only thing that making me hesitate is; I was talking to a diesel mechanic about it and they said doing a valve adjustment on such a high mileage engine could be risky for the piston rings (as up to this point both the rings and valves have aged together). Granted he works in diesel and not 3.4s so it’s totally different but his statement did make me think a little more. I don’t have experience with this area so heck if I know.

But I am leaning towards an adjustment regardless, thanks for your input.

 

So I adjusted my valves last summer while I was doing a valve cover job. Ironically, I was at exactly 278k miles (I meticulously document all work I do on my truck). I track gas mileage every tank as well, and correcting 9 valves that were out of spec did result in a 1-2 mpg increase (used to average about 14-14.5 mpg, since then I've averaged 15.9-16.4; all city driving). On more of a subjective side, it absolutely felt like it revved a bit more lively and pulled harder after adjusting the valve clearances.

Moral of the story, I'd suggest getting them adjusted. Toyota recommends it every 60k for a reason.

 

@Nessal

 

At 278k I bet a few of them are out of spec. Are they machining the head with the camshafts still on? I know some people do it that way but I would personally take the opportunity to take it all apart and get everything in spec and inspect everything. If you already have the head off, it won't make any sense not to at least check the lash and readjust them. It's much easier to do when it's off especially for those valves near the firewall. It sounds like you actually removed the heads yourself and brought them to a shop and you will be reinstalling it. If so, then it's a no-brainer imo. Feeler gauges and shims are cheap. I think it goes without saying but if they are going to machine it with the valvetrain still on, make sure everything is at TDC.

Not exactly sure why that diesel mechanic is worried about the valves and rings "aging together". One is on the bottom and the other is on top. If his concern is that after adjusting the valves and it's sealing better that it would cause higher cylinder pressures, you would have needed to adjust them regardless because now you have a real problem. This is not a reasonable concern imo because if there is an issue, it will leak either up top or down low. Either way, you will have to fix it. Maybe something was lost in translation but I'd rather have higher compression than lower as long as it's consistent across the cylinders.

TLDR: I would adjust them.

 

Ah that’s awesome to hear. Glad all that improved for ya. These are the benefits I’m hoping to also experience after adjustment!

Also inspiring me to keep better maintenance records besides throwing receipts in the glovebox haha.

 

Thanks for the reply. Your explanation makes sense.

I am dropping my heads off tomorrow at the machine shop. The guy said they do valve adjustments “and anything else that needs doing”. This is my first time doing something like this so I’m not sure wether or not they’ll need the cams as well (I assume they would for an adjustment). I’ll have more info tomorrow.

I found a crack in the driver side head yesterday so most likely I’ll have to buy a new one which means I’ll only have to worry about getting one side adjusted. Silver lining I guess?

 

I guess you know they cant check your valve clearance until you stick em back on top of the engine...

they can pressure check the seats , and inspect valve rods.....but that's about it..


Head pressure test - YouTube

 

Why can't valve clearance be checked with the heads off?

 

IF you get a reman head or a new cast....they should be good...
however, when you get everything together....
a good mechanic double checks those again before bolting the cover on...

this is one of those things you cant trust others to do it right...price of failure is too high.


If... you find/or are a good mechanic....you shouldnt have any problems...

big IF.....

Tons of vids out there....its those old toyota people.....

 

Rings and valve clearances have nothing do to with each other. Adjusting valves on a high mileage motor is completely fine and should be done. However, it might be too late and you could have already burned valves if they’ve gotten tight. Here’s mine when I found I needed to replace a few:

 

since the heads are out/off...............
i would just take to machine shop
$350-$450 i paid $350 plus $40 to resurface fly wheel and for pair of heads during a short block rebuild on another car
mind you there was no catastrophic damage to heads...included new valve seats/valve lash adjustment
small price to pay assuming you want to keep vehicle
GL

 

I agree with your statement regarding the diesel head’s opinion…

However, don’t these motors use shim less buckets to set valve lash (I have a second gen…)?? That’s actually a pain in the butt to adjust because the cam shaft(s) have to come out to change a bucket. On the other hand it is a very long lasting design and rarely needs adjustments; as face and seat wear, so do the bucket and cam lobe, which tends to keep lash the same. I checked when I put different exhaust cam gears in my 4.0, and at 200k miles even the exhaust valves were still dead on. This process is done last, with the heads back on the motor, so you can turn the cams with the crank.

TDC is a piston position and you can’t have them all that way if they’re still on the crank. Not sure why that would matter anyway, because the heads will be off for machining. But no decent machine shop would deck the heads fully assembled either.

If I’m sending a head out, I would see if they can be ported, get a good seat grind, and likely new valves and springs at that mileage. Also measure the cams.

 

The 5VZ uses shims to adjust the lash. TDC as in making sure all the valves are closed. I have heard of people getting their valves nicked by careless shops. It sounds from the OP that his shop is decking it with everything on.

 

The 1st Gen Tacoma motors (2.7 3rz, and 3.4 5v) both use shims, and pulling shims to measure and then adjust (to adjust valve clearance) is actually pretty easy (the ones closest to firewall are a bit tough to get at), and the cam stays in.

 

Good to know about the shims. But what bearing does TDC have on heads separated from the block??

 

Making sure the camshafts aren't opening any of the valves. When you set the pistons at TDC, all the valves are full closed. With it off the vehicle, you can still turn the camshafts to get it into TDC orientation.

 

You can’t set all cylinders at TDC at the same time. It’s not called TDC anyway when the heads are off (piston position aside for now), but I think I know what you mean now. Still should not deck heads with cams installed. This isn’t even the correct way to disassemble the heads.