valves, tappet clearance

[deQuincey]

the manual says 0,25 to 0,30mm

i set them to 0,25, car runs good, and i have a bit of tickling noise, nothing exceptional

i recall some "old school mechanics" here saying that better 0,30, engine runs better and so on

i have recently met with 2 people that say 0,20 and 0,15 respectively, the later drives the coupe in the track every weekend

can we discuss this a bit ?

 

[Bwana]

If you want to get really hard core about the cam timing, decreasing the clearance adjustment advances the timing slightly and increases the duration I think. You'd never feel it on the street but I expect it might make a slight difference in a racing engine that has some sort of class restrictions on it's originality (i.e., no hot rod cams allowed).

Also, a lot of cams have an initial sort of "ramp" between the base circle and the lobe to prevent the rocker from being slammed by the lobe. Don't know if ours have that but you would think that increasing the clearance would negate that "ramp" and go immediately from the base circle to the lobe, not so good. And increasing the clearance would retard the timing and decrease the duration so in theory it might run cooler but again, I don't think you could really tell the difference.

 

[m5bb]

Setting valves to a tight setting is not a good thing to do. At least that's what I learned from engine builders and machinists.
As the engine warms up those clearances get smaller.
At some point the valve may not even close all the way.
Engines are designed so the valve (particularly the exhaust) needs to spend that small amount of time on it's seat to transfer the heat from the valve to the cylinder head so the heat can be reduced in the valve or you will get warped valves.
The M30 motor is not the quietest motor and some valve noise is very normal.
So here's another way to adjust the valves that takes out some issues of wear.
Instead of using a feeler gauge at the top of the valve do it at the cam side of the rocker.
The measurements are slightly different but this takes out any wear issues that might be at the tip of the valve and cause an inaccurate setting.
I've been doing this for years and so have thousands of others. This idea came from FAQ on myE28.com where probably the most M30 motors reside.
Here's the link.
http://www.mye28.com/viewtopic.php?f=9&t=28172

 

[deQuincey]

all this is interesting info, keep it comming

i would say something that i have experienced and puzzles me, when i start the car the tickling noise of the valves is lower that when it warms up, so, why ?
anyone has experienced this ?
should this be a chance of telling us that gap increases with heat and not the contrary ?

 

[Honolulu]

But is the louder ticking noise on a warm engine due strictly to the valves, or other clearance issue(s)?

Could be that as things warm up, clearances decrease, contrary to your suggestion that gap increases with heat.

Recall the we're supposed to set the clearances with a cool or cold engine, so that the gap is reduced as the engine warms up. Why no set the clearance hot, as it would be when the motor is running?

 

[deQuincey]

But is the louder ticking noise on a warm engine due strictly to the valves, or other clearance issue(s)?

Could be that as things warm up, clearances decrease, contrary to your suggestion that gap increases with heat.

Recall the we're supposed to set the clearances with a cool or cold engine, so that the gap is reduced as the engine warms up. Why no set the clearance hot, as it would be when the motor is running?

thank you Charlie,

My guess is that only valve noise is involved in my comparison

in a conventional world heat decreases clearances, but this M30 might not be a linear system, i mean there are a lot of elements involved, made of different materials, so relative termal elongations might go one way or the other in the final system, i do not know all the details, i am only presenting a fact, valve noise increases,...
1- only my case ?
2- if general, what does that mean ?

clearances must be set with cold engine, yes, but that is only for having a common reference, it does not mean that warm engine will go in one direction or in another

we could set clearance in a hot engine if bmw provides the right figures to do so, i have not found such figures,...

 

[deQuincey]

Setting valves to a tight setting is not a good thing to do. At least that's what I learned from engine builders and machinists.
As the engine warms up those clearances get smaller.
At some point the valve may not even close all the way.
Engines are designed so the valve (particularly the exhaust) needs to spend that small amount of time on it's seat to transfer the heat from the valve to the cylinder head so the heat can be reduced in the valve or you will get warped valves.
The M30 motor is not the quietest motor and some valve noise is very normal.
So here's another way to adjust the valves that takes out some issues of wear.
Instead of using a feeler gauge at the top of the valve do it at the cam side of the rocker.
The measurements are slightly different but this takes out any wear issues that might be at the tip of the valve and cause an inaccurate setting.
I've been doing this for years and so have thousands of others. This idea came from FAQ on myE28.com where probably the most M30 motors reside.
Here's the link.
http://www.mye28.com/viewtopic.php?f=9&t=28172

@m5bb Setting valves to a tight setting is not a good thing to do..., yes, but the contrary is also bad, big valve gap may result in overheating,...

thank you for the e28 tip, i will take alook to that

 

[deQuincey]

oooouuuuuchhhhhh ! look at the red text :-O

from the e28 link:

"Problem: Valves tick or no valve adjustment has been done for some time
Cause: Gap clearance gets bigger as engine gets used. It's typical for M30s
How To Fix:
Tools: Special tool (Can be made by bending a piece of aluminum rod/hex wrench/hanger [This tool is used to turn the eccentric. You stick one in the hole of the eccentric and use it as a lever to turn the eccentric.]), wrenches, feeler gauge, screwdriver
1.Remove air box/any vacuum hoses
2.Unplug spark plug wires
3.Remove valve cover vent hose
4.Unbolt other circled areas
5.Remove Valve Cover (9 bolts)
6.Figure out which pair of valves are TDC (Top Dead Center) and adjust those. (Engine is slanted so the lobes are facing downward perpendicular to the pison(not perpendicular to the ground)) Loosen nut on rocker arm. Slide Feeler gauge in between the rocker arm and cam shaft. Place special tool in hole and rotate until it is snug. You should be able to move the feeler gauge around with resistance in between the eccentric and the valve. It is possible to compress the feeler gauge and get a false adjustment. Retighten the nut with feeler gauge still between.

Warm engine use .014in Cold engine use .012in
I had a Schrick 282 cam so my mechanic suggested .013in
Stock: pre ~82 M30's .010-.012 was spec'd rather than the .012-.014 as on later cars"

so if cold engine should be set to 0,012 and warm engine should be set to 0,014, that probably means that clearance increase with heat !!!
is this possibly true ???

 

[mulberryworks]

all this is interesting info, keep it comming

i would say something that i have experienced and puzzles me, when i start the car the tickling noise of the valves is lower that when it warms up, so, why ?
anyone has experienced this ?
should this be a chance of telling us that gap increases with heat and not the contrary ?

A friend of mine, gear head from way back, told me of setting the valves on an early Chevy engine. He said you set them with the engine running. The screwdriver you are making the adjustments with, ahem, oscillates in your hand. Don't know what the setting was but it sounds entertaining.

 

[Mike Goble]

A friend of mine, gear head from way back, told me of setting the valves on an early Chevy engine. He said you set them with the engine running. The screwdriver you are making the adjustments with, ahem, oscillates in your hand. Don't know what the setting was but it sounds entertaining.

This is a common practice with hydraulic lifters, oil everywhere, set them by sound, clean up the mess.

 

[m5bb]

Get the clearances increase with heat out of here.
That is just not true. Metal expands when heated. That's why we have tolerances for all bearings and pistons, etc. to allow for expansion.

Yes, the settings for a warm engine should never have been put in the FAQ from myE28.
All settings should be done from a cold engine.
Did you understand though that setting at the valve stem where there may be abnormal wear can cause errors in the actual running clearance.

 

[lloyd]

all this is interesting info, keep it comming

i would say something that i have experienced and puzzles me, when i start the car the tickling noise of the valves is lower that when it warms up, so, why ?
anyone has experienced this ?
should this be a chance of telling us that gap increases with heat and not the contrary ?

Could the increased noise be related to your motor oil? As its temperature increases, perhaps it changes relative viscosity? (Some of the noise may also be from loose rocker/tappet bearings or worn rocker shafts, which can be affected by changes in oil pressure. All things being equal, all valve train components should be operating at the same/consistent temperatures. But this is arguably not always the case, which is why some components can seem slightly more prone to wear than others, depending upon location within the engine. Hint, a spray bar with different sized holes or holes that are partially occluded can deliver more or less oil to valve train components and this could result in components with slightly different operating temperatures.)

Heat is also interrelated with oil pressure. As you know, when your engine has reached normal operating temperature, your oil pressure is probably lower than when it is cold. Depending upon machined metal to metal tolerances, lower effective oel pressure can mean slightly increased working tolerances and more noise. Obviously, different metals can have different expansion rates - so the explanation is overly simplistic.

 

[m5bb]

Could the increased noise be related to your motor oil? As its temperature increases, perhaps it changes relative viscosity? (Some of the noise may also be from loose rocker/tappet bearings or worn rocker shafts, which can be affected by changes in oil pressure. All things being equal, all valve train components should be operating at the same/consistent temperatures. But this is arguably not always the case, which is why some components can seem slightly more prone to wear than others, depending upon location within the engine. Hint, a spray bar with different sized holes or holes that are partially occluded can deliver more or less oil to valve train components and this could result in components with slightly different operating temperatures.)

Heat is also interrelated with oil pressure. As you know, when your engine has reached normal operating temperature, your oil pressure is probably lower than when it is cold. Depending upon machined metal to metal tolerances, lower effective oel pressure can mean slightly increased working tolerances and more noise. Obviously, different metals can have different expansion rates - so the explanation is overly simplistic.

Like the HINT: Have you checked the oil spray bar that runs across the rocker arms. The banjo bolts are notorious for getting loose and then the oil is not being sprayed. They should be safety wired or installed with lock tite. Here again many stories on MyE28.com about this occurrence.

 

[deQuincey]

Get the clearances increase with heat out of here.
That is just not true. Metal expands when heated. That's why we have tolerances for all bearings and pistons, etc. to allow for expansion.

Yes, the settings for a warm engine should never have been put in the FAQ from myE28.
All settings should be done from a cold engine.
Did you understand though that setting at the valve stem where there may be abnormal wear can cause errors in the actual running clearance.

thank you for your post
see the news, it is true, do you understand that clearances may increase with heat ? it is not a linear system, so why not ?
proof is not only your own link, but the blue manuals (a note in the footpage), and even mercedes manuals saying that for a warm engine gap should be fitted at +0,05mm with respect to cold engine setting
why do you refuse these facts ? metal expands when heated ? (not all of them, i.e. zirconium tungstate exhibits the so-called "negative thermal expansion,", yeah irrelevan, but...), so what ? it is a combination of metals and geometries, it is not only posible, it is true !

i did understand what you said about valve stems, but my valves are almost new, so no case here

Could the increased noise be related to your motor oil? As its temperature increases, perhaps it changes relative viscosity? (Some of the noise may also be from loose rocker/tappet bearings or worn rocker shafts, which can be affected by changes in oil pressure. All things being equal, all valve train components should be operating at the same/consistent temperatures. But this is arguably not always the case, which is why some components can seem slightly more prone to wear than others, depending upon location within the engine. Hint, a spray bar with different sized holes or holes that are partially occluded can deliver more or less oil to valve train components and this could result in components with slightly different operating temperatures.)

Heat is also interrelated with oil pressure. As you know, when your engine has reached normal operating temperature, your oil pressure is probably lower than when it is cold. Depending upon machined metal to metal tolerances, lower effective oel pressure can mean slightly increased working tolerances and more noise. Obviously, different metals can have different expansion rates - so the explanation is overly simplistic.

do not think is so relevant,
it is true, oil gets thinner when hot and pressure decreases, but all that has been considered in the design of the oils
my banjo bolts are in their place secured with loctite and Steel wire

i must admit that valve tappet clearance is not what I thought,....or maybe i am wrong

 

[m5bb]

deQuincey,
I think we are saying the same thing in a different way.
As I said earlier we seem to agree that metal expands.
What was different and I didn't understand what you meant was that the settings for a warm engine should be larger because it has expanded.
Yes, that is true. I'm just so used to all the specs being for a cold engine.

 

[deQuincey]

deQuincey,
I think we are saying the same thing in a different way.
As I said earlier we seem to agree that metal expands.
What was different and I didn't understand what you meant was that the settings for a warm engine should be larger because it has expanded.
Yes, that is true. I'm just so used to all the specs being for a cold engine.

@m5bb probably, first of all let me say that i do not want to win "the argument", i am trying to understand and learn and i thank you very much for your response,

I think we are saying the same thing in a different way. .....maybe, lets see...

As I said earlier we seem to agree that metal expands. .....yes metal expands, but the complex geometry of all those metallic elements may result in the case of the tappet clearance being enlarged when hot (as it seems to happen), and not reduced (as it might be expected)

What was different and I didn't understand what you meant was that the settings for a warm engine should be larger because it has expanded. ....but this is my basic point here, the reason why i started this thread:

everybody was telling me that the gap or the clearance in a warm engine was less than that in a cold one, so everybody was telling me to set the cold gap at 0,30mm because gap will be reduced when warm,

and what i am demonstrating here is: that statement is untrue,

gap increases when engine is hot, so is better to set cold gap at 0,25 or even 0,2 (as my friend did) because it seems that a warm engine will increase that gap in +0,05mm

two facts:
- my engine is less noisy when cold than when hot (good oil, new elements, overhauled engine, and the proverbial carefulness of dequincey)
- the books state smaller gap for cold setting than that for warm setting

Yes, that is true. I'm just so used to all the specs being for a cold engine ... i do not question this, gap should be adjusted in a cold engine (bascially because a warm engine will burn your fingers )

hope that now is clear what i try to demonstrate and thus learn....if i am not wrong

 

[lloyd]

do not think is so relevant,
it is true, oil gets thinner when hot and pressure decreases, but all that has been considered in the design of the oils
my banjo bolts are in their place secured with loctite and Steel wire

i must admit that valve tappet clearance is not what I thought,....or maybe i am wrong

I do not think anyone is disputing the fact that metal expands with heat and that the valve lash or tappet clearances get smaller as the various metal components expand. However, I was just trying to offer an explanation for why you seem to notice more engine noise from a hot engine than a cold engine. Engine lubrication may seem simple, but it is a complicated subject involving words that are difficult for me to spell let alone explain, e.g., hydrodynamics and elastohydrodynamics.

After an engine is run hard, it often sounds different than when cold. Some of the parts can be starving for oil, especially when engine speed is reduced to idle and, correlatively, when oil pressure is also reduced. This is one of the reasons for cool down laps or running an engine at fast idle prior to shut down. Oil pressure is significant as it both cushions and lubricates moving parts as well as removes heat, and oil exhibits different characteristics with temperature, including viscosity/thickness and flow. Of course, parts are designed to incorporate working tolerances, but different parts and different metal compositions expand at different rates relative to different temperatures. So, even though valve to rocker clearances are smaller when the engine heats up, the characteristics of the oil in your engine may not provide the same - boundary lubrication, cushion, flow, resistance and/or metal-to-metal protection - as when cold. Less "cushion" or protection between reciprocating metal parts generally results in more noise.

Multi-viscosity oils are supposed to retain or increase their viscosity when warm, but not all oils are the same, and not all machined moving parts are the same. In other words, when your engine is warm, even though the metal parts have expanded, the oil may not provide the same boundary lubrication that it provides when the engine is cold or when the engine is at speed and the oil is under significantly more pressure than at idle or slightly faster than idle. That so-called oil "cushion" functions to occupy greater clearances found in "worn" metal parts, that can contribute to valve train noise, e.g., worn rocker bushings or worn rocker shafts. It is also why heavier weight oil and engine viscosity treatments such as STP, or Wynn's Friction Proofing, Casite Motor Honey and the like, may result in a quieter running engine. Of course, quieter, may also mean reduced performance since thicker engine oils tend to create more parasitic drag between moving parts.

Different oils of the same viscosity can seem to contribute to different noises. An engine running clean, uncontaminated/undiluted, oil tends to make slightly different (less) noises (when at operating temperature) than dirty, contaminated, oil. More stable synthetic oil tend to flow better and offer greater metal-to-metal boundary lubrication than thicker conventional oils, but they are no substitute for large metal-to-metal clearances found in older engines and significantly worn engines

And no, I am NOT advocating that your engine needs these oil additives or related products, - although the graphic decals on the side of your coupe would make an interesting statement.





"The Racer's Edge"

Not oil viscosity improvers, but may improve oil flow

Examples of properly set tappet clearances?

Improperly set valve lash?:eek:

 

[deQuincey]

I do not think anyone is disputing the fact that metal expands with heat and that the valve lash or tappet clearances get smaller as the various metal components expand. However, I was just trying to offer an explanation for why you seem to notice more engine noise from a hot engine than a cold engine. Engine lubrication may seem simple, but it is a complicated subject involving words that are difficult for me to spell let alone explain, e.g., hydrodynamics and elastohydrodynamics.

dear @lloyd
impressive text thanks, all about oils, good, but i am afraid there is a base issue that we "are disputing":

I do not think anyone is disputing the fact that metal expands with heat and that the valve lash or tappet clearances get smaller as the various metal components expand

i am disputing this, precisely

in my humble experience + opinión VALVE CLEARANCES GET BIGGER (+0,5MM) IN A HOT ENGINE with respect to the same cold engine
;-)

 

[Bwana]

We'd have to look at the geometry of the valve train to know for sure. Anyone have a sectional view of same? i.e., an end on shot of the valves/cam/rockers? Something like this article but for our specific engine (pretty good article BTW). Then it would be relatively easy to understand where everything goes when it heats up and expands.

http://www.hotrod.com/articles/ctrp-0611-rocker-arm-valvetrain-geometry/

Lloyd, thanks for the pictures! I'd forgotten how many Snake Oil products were out there. You all do realize Marvel Mystery Oil was mostly kerosene?

 

[m5bb]

I have sent some inquires out to two engineer friends to see what they say. One is a machinist and the other is a tuning engineer for some race teams. Both have degrees from Georgia Tech.

But while were waiting have you ever actually tried this. Set the valves then drive or warm the engine and measure them again. I did read that one reason we always set them cold is that
the temperature is more stable. On a warm engine as soon as you shut it off and by the time you can get the valve cover off the valves will had dropped temperature by a couple hundred degrees or more so those measurements are still not at the true operating temp.