Valve adjustment interval? (1 Viewer)

[Slow Left]

I eventually want to desmog the fj60, but now this worries me.... Ah well something else to research and learn.

No need to worry...take another look at the thread (especially the explanation in post #20) and you'll see that the myth is that removing the Air Injection system during desmog will cause (lead to) the valves burning.

Instead, as Jim points out in post #20, there are two root causes for valves burning:

"There are 2 things which burn the exhaust valve:
1. Tight adjustment, which does not let the valve come into solid contact w/ the cold seat long enough to drop the temp of the valve.

2. A lean combustion event that leaves superheated oxygen in the chamber. When the exhaust valve pops open and the glowing hot oxygen goes past the exhaust valve it attacks it in the same manner as an oxy-fuel cutting torch.

The AP can not stop the valve burning, because the valve burns when it is open. When the exhaust valve cracks open and cylinder blowdown begins, flaming hot gas is leaving at near sonic velocity and several hundred PSI. A little squirt of fresh air downstream of the valve is less than insignificant at that critical moment.

The valve can not burn if there is no free oxygen left in the chamber after combustion. If the mixture is correct or richer, valves don't burn. If the mixture is 18:1, and the valves are not Stellite or another inox alloy, then they are toast."


So, I think by cleaning (Seafoam etc.) and adjusting the valves each year you can mitigate #1 from happening.

And making sure that you don't have any vac leaks and that the carb is tuned correctly so that you are running 14:1 mixture and NOT a lean 18:1 mixture, then you are mitigating #2 from happening...

...I wonder if there is a way to directly measure air:fuel mixture?

Also, I'd still like to find out:
What constitutes a tight/loose valve (and how is it measured....for example, one thousandth or two thousandth off spec?)?
What are the implications of running loose valves?

 

[Slow Left]

Think I'll skip this step! Haha

Yeah, really...notice in the video apparently feeler gauges are optional...

...but a dog is required, tho...

 

[gregnash]

So I have a question, this is on my agenda of things to do to BeBe..... since you already have the VC off there is no harm in starting the engine with it off is there?
I have not read through the thread that SL linked but what I am thinking of for hot adjustment is that you go through most of the adjustments while the engine is still hot. Then as the valves cool towards the back start the engine and get up to operating temp and then finish it off. Is there an issue with doing this? From there I would let the engine cool and check the cold settings, or would have done that first.

 

[Slow Left]

since you already have the VC off there is no harm in starting the engine with it off is there?

There is no harm in running the engine with the valve cover off. The oil is not pressurized under the valve cover to the degree it is with other engines, so on the 2F oil will not go flying around with the valve cover off...
Just be sure not to drop anything that might get stuck in the springs, etc..

...hot adjustment is that you go through most of the adjustments while the engine is still hot. Then as the valves cool towards the back start the engine and get up to operating temp and then finish it off. Is there an issue with doing this?

If you are going to adjust the valves 'hot', then it probably is a good idea to rewarm the engine if it is taking a long time. Just have to make sure that you have kept track of what is adjusted/loose still. LAMBCRUSHER says in an earlier post that he will rewarm the engine and even check valve clearances with the engine running and go back and redo any valves that are still out of spec..
Just remember that you are going to have to find TDC compression again for those valves you will go back and adjust once the engine is rewarmed...

From there I would let the engine cool and check the cold settings, or would have done that first.

There is no need to do both 'hot' AND 'cold' adjustement. Note that the FSM calls for you to adjust the valves with the engine 'hot' (but not necessarily running...there seems to be some confusion in the FSM but general agreement on MUD that valves are not to be adjusted with the engine running...)
But some of the discussion in this thread and other threads is whether or not the valves should be adjusted cold at all...and if it is OK, then what feeler gauge to use to compensate for the fact that you are adjusting them 'cold'...I adjusted them cold using the specs from the chart posted in the thread I link in post #6 of this current thread..

 

[Output Shaft]

The benefit of CHECKING the valve lash while the engine is hot and idling is you can feel for certain what the valve lash is on all the valves while they are tapping up and down. If you can slide a 0.016mm (or larger) feeler under an exhaust valve stem while the engine is idling, the valve is too loose and you will hear it. If a 0.014mm feeler can't fit in the gap while the engine is idling, the exhaust valve is too tight. Same methodology for the intakes.

IMO, checking valve lash with a hot idling engine is the quickest and most reliable way to know for certain what the gap is. All 12 valves can be checked (with 2 feeler gauges) in under 2 minutes or less when the engine is hot & idling by just quickly sliding in a feeler and noting the fit.

On a VERY side note, the first few years I owned my FJ60 in 88-90, I used Castrol 10W-40 or 20W-50 conventional dino motor oil. The valves got out of adjustment regularly, and by 15,000 miles most of them would be tight. Valve adjustment was a regular thing. Then when Castrol Syntec 5W-50 came out (all synthetic oil) I gave it a try.... and noticed that I almost never needed to adjust the valves again... They would not need adjusting for maybe 40,000 miles or more, and when they did get adjusted the re-gapping was minimal. That would have been impossible with dino oil.

[EDIT] So this clearly points to one of the main causes of tightening valves: Valve train wear. Cam, lifters, pushrods, rockers, valve stems.. all wearing out.

 

[Chester]

<$0.02 worth

3FE with lot's of miles. rocker faces have been cupped for years, probably needs a valve job.
I always check and and adjust with engine idled up and warm. It doesn't throw any oil, but a polypropylene rag tucked past the rear end of the head keeps any oil from flowing off the back. I run through them pretty quick, may loosen a few exhaust valves, tighten a few intake, whatever. On recheck with the engine off, it's obvious the cupped faces meeting the rods occur at a wider opening than indicated.

 

[augirthedude]

"So this clearly points to one of the main causes of tightening valves: Valve train wear. Cam, lifters, pushrods, rockers, valve stems.. all wearing out." Output Shaft

Valve train( cam, follower, rocker, pushrod) wear will increase(loosen) the valve to rocker clearance. Valve to valve seat wear will cause decrease(tighten) valve to rocker clearance .

 

[Output Shaft]

"So this clearly points to one of the main causes of tightening valves: Valve train wear. Cam, lifters, pushrods, rockers, valve stems.. all wearing out." Output Shaft

Valve train( cam, follower, rocker, pushrod) wear will increase(loosen) the valve to rocker clearance. Valve to valve seat wear will cause decrease(tighten) valve to rocker clearance .

You are absolutely correct! How did I get that wrong? 3rd grade logic musta been too much for me... Man.. I should take a break from this forum..... I wonder why the change to syth oil decreased the need for valve adjustments..... hmmm. Thanks for bringing my donkey logic to light.

Unless... the sick truth is that the synthetic oil INCREASED the wear to the valve train so that valve train wear and valve seat wear became equal, which would explain why the valves "adjusted themselves". Now I am feeling in my stomach......

 

[LAMBCRUSHER]

OS down the rabbit hole...hehehe. who suggested to not overthink things?

 

[Slow Left]

OS down the rabbit hole...hehehe. who suggested to not overthink things?

Ha, ha! Welcome, OS...we've been expecting you...as you can see, there is plenty of room for all of us down here...

 

[Output Shaft]

 

[Slow Left]

Hilarious! I've got that same mod on my 2F!

 

[60Works]

It's likely that the reason Toyota specifies setting the gap with an 'operating temp' engine is the same as a cooking recipe requires a preheated oven. It is a universal starting point so that the baking time instructions are accurate. Ambient temperatures vary greatly and constantly. 'Operating temp' varies little despite ambient temperatures varying greatly and constantly.

I've tried to check the valves with the engine running. It's a horrible method. It's dangerous, very messy, impossible to torque the nuts evenly, and smashes your feeler gauges flat so that they are inaccurate evermore. The 3FE manual instructs to check the lash with the engine off because it can't run with the valve cover off.

Get it warm. Set at TDC and check. Check it all again. Set at TDC +360 and check. Check it all again. Put it all back together and wonder why you have an unexplained unconnected vacuum hose.

 

[Chester]

It's likely that the reason Toyota specifies setting the gap with an 'operating temp' engine is the same as a cooking recipe requires a preheated oven. It is a universal starting point so that the baking time instructions are accurate. Ambient temperatures vary greatly and constantly. 'Operating temp' varies little despite ambient temperatures varying greatly and constantly.

I've tried to check the valves with the engine running. It's a horrible method. It's dangerous, very messy, impossible to torque the nuts evenly, and smashes your feeler gauges flat so that they are inaccurate evermore. The 3FE manual instructs to check the lash with the engine off because it can't run with the valve cover off.

Get it warm. Set at TDC and check. Check it all again. Set at TDC +360 and check. Check it all again. Put it all back together and wonder why you have an unexplained unconnected vacuum hose.

That's probably not the reason for bringing it up to temp.
3FE runs fine with the cover off, it doesn't throw oil at all, every nut get's torqued identical, and I'm using the same feelers I've always used.
Next sunny day, I'll get my Granddaughter to film a valve adjustment, I won't put it on a trailer, or set the idle with a brick though.

Back to the OP question; interval as spec'd in the FSM is probably too frequent for a 10-20K yr. truck, but if you're only doing half of that, every 2 or 3 years is probably often enough, YMMV

 

[Slow Left]

Borescopes will not let you see if a valve is not seating correctly and leaking. In fact, even when the head is off and tilted on it's side so you can peer at it close up...with a magnifying glass, there is no way to visually tell whether a valve is leaking or not. Leaking valves usually look just like properly seating valves. As augirthedude mentioned, a compression test is the best way to check for leaky valves when the head is installed. Carbon build up on the valve is mostly detrimental on the stem side of the valve which could be visible from the port on the head via a journey down the carb and manifold using an expensive articulating borescope (not the one from HF). See borrowed web pic below (not a LC engine)
View attachment 1002767

Valves can be kept clean by using good quality gasoline, running the engine up to full operating temp often, or spraying a little water mist or carb cleaner/sea foam into the intake of the hot running engine every blue moon.

Cool. Thanks for the excellent clarification (as always) OS!

Yeah, I was referring more to using the visual inspection (via borescope) for checking for discoloration of the face of the valve (rather than trying to inspect the seats) as an indicator of conditions of a burnt valve.

View attachment 1002813

I'm definitely going to add valve adjustment to my annual maintenance regime, since I have a fairly low mileage 2F (~200k miles) in good working order (except for some minor piston slap while warming up).

Also a fan of the Seafoam treatment in both the gas tank and crank oil...although I think next year I'm going to pipe the Seafoam directly into the carb fuel bowl through the vent tubes (I'm lazy and don't want to remove the air horn) instead of into the fuel tank...I have a feeling that stuff eats away at the rubber fuel lines I have installed...

I also use StarTron as a fuel additive every once and a while, which helps keep the bacteria undercontrol (especially with all the ethonal being added into the gasoline).

@Output Shaft , it just crossed my mind that inspecting the discoloration of the spark plug electrodes should provide the same information on 'burn' conditions in the cylinders as trying to inspect the face of the valves with a boroscope...and simpler, too...

So if the cylinders are burning the correct 14:1 air:fuel ratio, I presume one would expect to see 'mocha' colored electrodes (after a long period of time running those plugs)...?

 

[Output Shaft]

@Output Shaft , it just crossed my mind that inspecting the discoloration of the spark plug electrodes should provide the same information on 'burn' conditions in the cylinders as trying to inspect the face of the valves with a boroscope...and simpler, too...

So if the cylinders are burning the correct 14:1 air:fuel ratio, I presume one would expect to see 'mocha' colored electrodes (after a long period of time running those plugs)...?

Yes, & Yes.

...I was referring more to using the visual inspection (via borescope) for checking for discoloration of the face of the valve (rather than trying to inspect the seats) as an indicator of conditions of a burnt valve.

ohh,
Perhaps the term "burnt valve" is misleading.
The term "burnt valve" [as I understand it] is incorrectly used to denote a WARPED valve or LEAKING valve that has deformed due to overheating and no longer seals properly. The term "burnt" has nothing to do with the black or brown deposits seen adhering to the valve. And since the term has a bad-ass ring to it, people use it.

Valves that are coated with black or brown or white deposits can seal fine… or they can all be warped and leaking. There is no way to tell by just looking at them.

As another side note, the universally hated EGR system on the 2F lowers the maximum combustion temperature, and by doing so, it lowers the formation of NOx smog. That is it's purpose. But as a side effect (along with strangling the power out of the 2F), the EGR system lowers the exhaust gas temperature of the gas screaming past the exhaust valves which will help to prevent them from overheating and …… burning.

Something for all of us to remember who have disconnected the EGR… The EGT is now hotter, which means the risk of exhaust valve "burning" is now higher. No free lunch.

 

[jlhollowx13]

Yes, & Yes.



ohh,
Perhaps the term "burnt valve" is misleading.
The term "burnt valve" [as I understand it] is incorrectly used to denote a WARPED valve or LEAKING valve that has deformed due to overheating and no longer seals properly. The term "burnt" has nothing to do with the black or brown deposits seen adhering to the valve. And since the term has a bad-ass ring to it, people use it.

Valves that are coated with black or brown or white deposits can seal fine… or they can all be warped and leaking. There is no way to tell by just looking at them.

As another side note, the universally hated EGR system on the 2F lowers the maximum combustion temperature, and by doing so, it lowers the formation of NOx smog. That is it's purpose. But as a side effect (along with strangling the power out of the 2F), the EGR system lowers the exhaust gas temperature of the gas screaming past the exhaust valves which will help to prevent them from overheating and …… burning.

Something for all of us to remember who have disconnected the EGR… The EGT is now hotter, which means the risk of exhaust valve "burning" is now higher. No free lunch.

Can this extra risk of burning a valve without the egr in place be remedied or at least lower the risk if higher octane fuel is used?

 

[Slow Left]

The term "burnt valve" [as I understand it] is incorrectly used to denote a WARPED valve or LEAKING valve that has deformed due to overheating and no longer seals properly.

Ok, right, so the term 'burnt' refers to the condition of the seat of the valve and valve seat on the head...a valve is 'burnt' when it doesn't seal correctly.

And if there are two conditions that lead to valves 'burning' (tight valves or 'lean' combustion conditions), then I was making the connection between the color of the valve faces as an indicator on the combustion condition...and then realized that the color of the spark plug electrodes might equally serve as an indicator to the combustion condition, alleviating the need for boroscoptographologyism (...?...)...

 

[Output Shaft]

boroscoptographologyism

hexaboroscoprialogianism is actually the correct term...

Yes plug color after a long run will give a rough indication of combustion behavior. [So I've heard]
A valve that was improperly ground could leak though it had never burnt. But typically a valve that used to seal fine, but then started to leak, overheating is likely the cause.

{in summary}
Tight exhaust valves can overheat and warp when the rocker adjustment is too tight because the tight rocker is preventing the valve from resting on the seat of the head...or does not allow it to seat for a long enough period of time. The exhaust valve needs to cool down sufficiently on the intake, compression and power stroke while seated on the relatively cooler head valve-seat before the next blast furnace from the exhaust stroke engulfs it.
Properly adjusted exhaust valves can still burn out of shape if they become overheated. I have witnessed this first hand. Leaner than safe fuel mixtures and a malfunctioning cooling system are always the suspect.

>>>>

Combustion temperatures that are hotter than "normal" occur when a properly functioning EGR system is disconnected. Lowering combustion temperature is the reason an EGR system is installed on the engine in the first place to reduce NOx smog. Higher combustion heat does not equate to a proportional rise in generated power. You get a bit more power at the cost of a lot more heat when the fuel mixture leans out towards 14.7:1, which is above the ratio the engine/fuel delivery system was designed for.

The EGR is replacing OXYGEN, with dead inert exhaust gas. This creates a richer mixture in the combustion chamber compared to no EGR. Richer mixtures burn cooler because the heat capacity of the gas charge is greater due to the fact that unburnt hydrocarbons can absorb more heat.

Whether the EGT resulting from no EGR can be so hot as to deform the exhaust valves in short order is debatable...but over time??? All we know for certain is the EGT is hotter when the EGR is gone.

It does not seem likely that high octane gasoline could lower EGT. Perhaps someone more knowledgeable about flame front propagation could shed some enlightenment.

Although one sure way to keep the exhaust valves cool would be to mount several large cylinders of refrigerated compressed Argon gas into the back of the cruiser and have it metered into the EGR valve while driving....I myself, (like a snot-nosed kid addicted to Pixie Stix & Mountain Dew) will still be running my engine sans EGR cuz I just LOVE the POWER.

& anyway, who cares about the minor nuisance of a complete head rebuild every 5 years?

 

[Slow Left]

hexaboroscoprialogianism is actually the correct term...

Ha Ha! ...I forgot it was 6 sided...thanks for the correction...

The EGR is replacing OXYGEN, with dead inert exhaust gas. This creates a richer mixture in the combustion chamber compared to no EGR.

Right, so if you remove EGR, then adjust the air: fuel ratio to the correct ratio for complete combustion, then you should be good...