Sanity check on engine geometry

[MapisM]

Premise: boat sheltered and wintered, engines expected to not move for 7 months overall.
Suggestion received from an official engineer (MAN as it happens, but I don't think this matter): every month or so, rotate the engine manually, in order to not leave the very same valves open/close for the whole timeframe (changing also the raw water impeller position, as a by product).

Note: You are allowed to comment on whether the suggestion makes sense or not, but only as long as it's not an excuse to avoid the real questions , which are...

1) By how many degrees should the engine be turned, in order to be sure that all valves which were previously open will close, and vv?
2) Should the engine be rotated CW or CCW (looking at it from the belts side, not the gearbox side)?
3) Does it matter whether the engine is rotated in the right direction anyway, since it would just be rotated manually and very slowly?

Of course I know what I was already told on the above, but don't ask me to spill the beans in advance...
I'm just not 100% convinced of that, so I thought that rather than squeezing my own head further, I could as well make some forum brains smoke...!

 

[BruceK]

Taking a bite and maybe a flyer too, but I'd guess...

1) one full revolution (360 deg) of the crank on the principle it's 720 degrees between (like) valve openings
2)Crank turned in it's natural running direction or cam chain slop might effect
3)yes it does matter as per 2

Edit

1 is wrong on retrospect. The answer must lie in number of cylinders / firing order and then the 720 degree rotation. You're right. My head is smoking

 

[Portofino]

If it’s “ hors service “for 7 months and a multi cylinder ( more than 2 ) which it’s ,then the less brain smokey method would be turn it any thing from 90 to 180 each time ( assume 7 ) .
This is to alter the valve spring tension evently on all of them near enough .

Redirection , if the impeller is left in then they need to turn in the same direction as running so,s not to reverse the impeller vanes .Of course if they have been winterised properly ( you have not said) the impellers will have been removed .
How ever there’s the other side closed cooling circuit to pump round ,in the correct direction unless this has been drained ,again you have not said .
I think they turn clockwise Looking from the flywheel/ G box end .Exact info is in the manual .

I like to run mine up ( boat stays in the water ) every month from Oct - May , but that’s a different Q .
Another thing I do with MAN. s they have a highly pressured closed cooling circuit .Its important to refresh the coolant for anti corrosion reasons as it goes off with time .
Rarther than do a full and messy total system drain every 3y or what ever, each Nov I drain off the header tank - easy electric pump out of say 5/6 L and repenish with new .This is circulated ,brought up to temp and pressure .
idea is beef up the anti corrosive element in the coolant , over the inactive winter period it’s € 50 imho well spent .

Geny engine is the ubiquitous Yanmar 1 GM 10 block , it’s a bit like a Hulux pick up , hard to kill, even so it gets run for 1/2 hour under load every month .
Air con gets a run out too , well the huge c alpeda pumps , idea is to prevent them ceasing up ,salt setting the impeller s
I fact all the pumps get a buzz monthly .
It’s only 65 CHF return easyJet from GVA to NCE , so I go every month , less than an hours flight .

Just TLC really the main engines are 2003 but eachto there own with winter regimes :encouragement:

 

[MapisM]

You're right. My head is smoking

LOL, sorry, but if it's any consolation, U R making mine smoke even more than it already did!
Why should the cylinders number matter...

 

[MapisM]

If it’s “ hors service “for 7 months and a multi cylinder ( more than 2 ) which it’s ,then the less brain smokey method would be turn it any thing from 90 to 180 each time ( assume 7 ).

Sorry L, but I can't for the life of me understand your reasoning.
Ain't it obvious that any valve which just began opening when the engine was stopped will still be open after a 90 deg crankshaft rotation?!?

 

[Portofino]

Sorry L, but I can't for the life of me understand your reasoning.
Ain't it obvious that any valve which just began opening when the engine was stopped will still be open after a 90 deg crankshaft rotation?!?

You are I assume working your way once a month ,so 7 ( could be 14 if two weekly ? ) through a returning process that fairly redistributes the spring L .
You can,t have em either fully open - max compressed or full close , max spring L in a V 8 or V 12 , amplified by 2 because they are unlikely to have stopped exactly at the same point .
So KIS , just turn it enough , divided into the episodes 7 , 14 or how ever many times in the lay up period .
I don,t think left in un moved for a few weeks will harm it spring wise ,on the other hand a turn now and again will do no harm and as said shuffle up the valve spring L and thus tension .
Hence a vague ish 90-180; answer will achieve what you want ,if reshuffling the valve spring tension is the object .
Hence none brain smokey method .
Hope that clarification works
Without the rocker box covers off you don,t actually know which valve are where open / shut wise anyhow
You are blind. So just as said turn it based on the number of episodes over the lay up period .
Easy peasey on the brain

 

[MapisM]

Mmm... 'scuse me, but I can't see any KIS principle in your reasoning.
Yes, I guess you can argue that if generically "reshuffling" the valves once a month throughout 7 months is the objective, then 103 degrees x 7 times is bound to be the mathematical answer...
But the original question #1 in my OP is different, and in a sense simpler - let me rephrase that:
Which is the miminum crankshaft rotation that assures you that ANY valve, in ANY cylinder which is open before the rotation will be closed afterwards?

PS: I didn't mention it, but not opening the covers is a given. Far too boring!

 

[Portofino]

Mmm... 'scuse me, but I can't see any KIS principle in your reasoning.
Yes, I guess you can argue that if generically "reshuffling" the valves once a month throughout 7 months is the objective, then 103 degrees x 7 times is bound to be the mathematical answer...
But the original question #1 in my OP is different, and in a sense simpler - let me rephrase that:
Which is the miminum crankshaft rotation that assures you that ANY valve, in ANY cylinder which is open before the rotation will be closed afterwards?

PS: I didn't mention it, but not opening the covers is a given. Far too boring!

Without whipping off the valve covers you have no idea what position the valves are in at the start of the excerise.
Hence the less brain smokey arbitrary turn range - KIS approach .
So just turn it a bit not 5 degrees of course but anything from 90-180 each visit , over the 7 months to reshuffle the spring L .
What have you done with the fluids ?
Presume the sea water drained out of the raw water pump @ lift cos nobody in the yard crawled into the ER to close the seacocks - right .. ? If so then the impellers are drying out — setting so to speak .
Should be taken out and covered in glycerol .?
Then as said your closed cooling s just sat there - thermostats gluing shut unless you are on top of the coolant change / refresh regime ,
Never mind the valve spring mothering what about the injector springs and solinoids ( if applicable ) along with any other sensitive internal parts inside the diesel pumps .Asumme “ turning “ the engines will be done without the key ignition on ?

Also silly Q how exactly do you propose to manually turn them ? In a confined ER ?? accurately any how if when the smoke clears in the brain you happen to calculate some notionally ideal angle ??

Kiss just turn them every now and again

 

[MapisM]

Also silly Q how exactly do you propose to manually turn them ? In a confined ER ??

That's the easier part. You might have noticed also in your engines a 32mm nut in the centre of the pulley, which is the only area left accessible by the belts cover.
It's sufficient to grab that nut between your finger and your thumb, and rotate it.
Alternatively, if you are one of those who use bottle openers, you might resort to a socket wrench...
I'll take a pic tomorrow, that's easier and quicker than explaining further!

Ref. the rest of the winterization, no worries.
Winterizing a boat is a total waste of time in CF, but up here in the N Adriatic winter temperatures can be pretty cold - one year, they had up to almost -20C in Jan, believe it or not!
So, no half decent yard would store a boat without running antifreeze in all raw water circuits (mains, genset, a/c), emptying fresh water circuit, sealing air filters, etc. etc.
All stuff I was already used to during the decade which I spent bating in the Adriatic, btw.

Back to the point, there's no need to know any initial valve positions, to be sure that any open one will be closed after an X degrees rotation. It's just a matter of understanding how much X is...
Now, where's LS1 when one needs him!?

 

[NBs]

Hi,

This was the first time I heard from the point of view of valves, why rotate the machine when it has not been used for a long time. I have been taught that the machine is slightly rotade so that the crankshaft will change the position relative to the bearing surface so that no dot point corrosion occurs because the crankshaft is the most expensive part of the machine. This guide is followed by Army, coast guards and other commercial vessels that will not be used for a long time.

And more importantly, the engine has fresh oils inside to protect against corrosion when the machine does not warm up regularly.

What say your engines owners manual???

NBs

 

[BruceK]

LOL, sorry, but if it's any consolation, U R making mine smoke even more than it already did!
Why should the cylinders number matter...

Because a 4 is 2x 180 in parallel a 3 is 3 x 120 in parallel. So for a 4 you'd turn 360 on the crank to rotate 2 strokes but on a 6 that would always leave 2 cylinders valves at 50% còmpression. ..... I think....oh my head hurts

 

[MapisM]

I have been taught that the machine is slightly rotade so that the crankshaft will change the position relative to the bearing surface so that no dot point corrosion occurs

Good point, NBs. I can see that this is another good reason, even if it wasn't mentioned by that engineer.
Anyway, that's not something I've ever found in any owners manual - also of other engines I came across in the past.

 

[MapisM]

Because a 4 is 2x 180 in parallel a 3 is 3 x 120 in parallel. So for a 4 you'd turn 360 on the crank to rotate 2 strokes but on a 6 that would always leave 2 cylinders valves at 50% còmpression. ..... I think....oh my head hurts

I can see why, because you are overcomplicating the problem.
Well, I think you are - if I were sure of the correct answer, I wouldn't have posted this thread, to start with!

Anyway, I believe that the simpler way of reasoning is as follows:
Forget how many cylinders the engine has, all you want is to close any valve which is open.
In any cylinder, aspiration valves open just before the top dead centre, and close just after the bottom dead centre.
For exhaust valves it's the other way round.
Now, isn't this enough to imply that by rotating the crankshaft by a bit more than 180 degrees any open valve will be closed, irrespective of their initial position?

PS: of course, some other valves which were closed will be open after that rotation, and it's impossible to know which and by how much. Anyway, upon the next 180+ rotation, any open valves will be closed again.

 

[Momac]

Someone I know has replaced his valves which were not seating, probably due to corrosion during long periods of inactivity. Mind you the engines are perkins and the parts are relatively cheap. Smoke free and much smoother running reported.

How would you go about rotating the engine manually ? Will the compression not prevent it ? Or do the injectors need to be removed ?
Perhaps arranging an engine oil change half way through the very long 7 month winter layup would be an appropriate compromise as I imagine the engines would need to be run up to warm the oil prior to removal.

 

[jfm]

Mapism, you're correct that # of cylinders is irrelevant. Answering precisely what you asked and I'm going to assume 4T:

Q1. There is no degrees of rotation that you can know will put all valve springs in opposite state.

Consider this, stated simply without considering overlaps and vat and all that. Imagine you're at bdc just as the compression stroke is about to start:

For first 180deg you have compression, all valves shut (= springs relaxed).
Next 180 is power stroke, all valves still shut.
Next 180 is exh stroke, so exh valve open.
Next 180 is induction, so inlet valve open.

Full cycle is 720 deg then you start all over again. So it is impossible to specify your X degrees whereby you know that whatever valve was open is now shut. It's either 180 deg or 540, but you cannot know which of those two numbers it is. In a multi cylinder engine it will typically be 540 for half the cylinders and 180 for the other half.

Q2&3
Direction usually doesn't matter for engine ( plenty of old boats reverse by stopping the engine and restarting by running the starter motor backwards) but it does matter for ancillaries like pumps so I would turn it the correct way. That's invariably ccw looking at flywheel/gearbox end. By your rules that is CW looking at the other end, but in engine speak you always quote rotation looking at the flywheel end.

Btw I'm not thinking of the rubber water pump- that's trivial. I'm thinking of hydraulic pto positive displacement pumps like power steering. These will be ruined by incorrect rotation, possibly just one rotation will kill it.

Btw, I don't buy the whole "rest the springs" theory and think it's bolx, but that's not what you asked. As I've said before, beware taking advice of that nature from a mechanic.

 

[MapisM]

Bingo.
All agreed J, except...

Full cycle is 720 deg then you start all over again. So it is impossible to specify your X degrees whereby you know that whatever valve was open is now shut. It's either 180 deg or 540, but you cannot know which of those two numbers it is. In a multi cylinder engine it will typically be 540 for half the cylinders and 180 for the other half.

In fact, I don't get the 180 or 540. Why shouldn't 180 be enough no matter what?
Let's stick to your reasoning of splitting the full 720 cycle in 4 sections of 180 each.
For any valve which is currently open, but near the end of its 180 opening cycle (say 175 degrees), just a small rotation (i.e. 5 degrees, in this example) will be enough to close it.
For any valve which just began opening (say it's at 5 of its 180 cycle), it will take more (175, in this example).
But the bottom line is that by spinning the crankshaft 180 degrees any open valve will be closed regardless.
By saying that it might take more than 180 for some valves, you imply that those valves are staying open for more, which is never the case.
Or am I misunderstanding what you are saying?

For the records, 180 was the suggestion of that chap, and the discussion we had is because I told him that 180 might not be enough, because it doesn't consider valve overlap.
I mean, in 4T engines afaik the inlet valve starts opening some degrees before the TDC, and the exhaust valve is completely closed a few degrees after. Same goes for the opposite (BDC): exhaust valve starts opening a bit before, and inlet closes a bit after.
That's the point (possibly a bit academic, I must admit) which I debated with that chap, because when I asked him how many degrees of valve overlap there is in my engines, both at TDC and BDC (if any, btw - afaik the theory is the one I just explained, but of course I'm not the one who designed MAN camshafts), he didn't know.
He said that he usually does 180, but he saw my point and suggested to make it 190 or so, just in case...
So, in this respect I can't argue with your last warning, and I'd love to hear the view of someone like LS1 who forgot more than most engineers will ever know about engine design.
But at the same time, I would think that it doesn't harm anything to do it - also for the reasons NBs mentioned, which make good sense, I reckon. :encouragement:

 

[MapisM]

How would you go about rotating the engine manually ? Will the compression not prevent it ? Or do the injectors need to be removed ?

Well, I don't think that in a very slow manual rotation any meaningful compression can be created.
But after I'll try later today I'll be able to tell you for sure. Anyway, I sure won't remove the injectors!

Running the engines half way during the winterization period might be a good idea, but it's a bit impractical in a closed shelter...

 

[Portofino]

In a multi cylinder engine it will typically be 540 for half the cylinders and 180 for the other half .

Nearly right ,that only applies say in a V8 ( which MapishM has here so its reasonable to use that ) with a flat plane crank ** .
Which I,am sure the MAN V8 is not .
It’s most probably arranged so they fire off in pairs , one on each bank of 4 .
If that s the case then every 1/4 of the two rotations to complete a cycle will see a pair reach TDC and another pair BDC , one pair exhaust closed ,one pair inlet open .
So based on that firing order 180 degrees seems reasonable advice from the mechanic .1/4 of the full 720 .
Problem is as I said above you don,t know which pair are where in the cycle .The manual will tell you which are the pairs.
Buts that’s irrelevant,as long as you know they work in pairs .

This brings me round to barring it .@ MapishM
You may be able to feel the two coming up to TDC .I say may as ( ingnore valve overlap in the sense of adjusting the spring L ) ,but like Martyn G ^^^ ,with a comp ratio of 16 + ? to 1 and massive pistons MapishM,s gonna need a pretty huge say 1m bar to turn those in a 18 L or so V8 on the crank pulls nut .
There is an inspection plate for setting up the timing ,which can be removed and a barring socket fitted .
Think of the cog on a starter motor with a 1/2 inch drive in the other end .With one of these “barring drives “ at least you have some gearing think how many teeth on the rim of the flywheel etc .to the dozen or so on the barring tool

MAN do a special ratchet ,special tool it only turns one way it’s used for setting the tappets .
From experience adjusting tappets on simple 4 cylinder say 2 L with a comp ratio of 9 to 1 ,you end up removing the spark plugs to ease the pressure ,never mind a 18 L diesel ! V 8 where as said a pair are coming on together .
Btw , you don,t wanna be able to easily turn it = zilch compression ,knackered rings

** Ferrari used to do a flat plane V8 in the 360 , 4 would fire at a time , hence huge power esp at high rpm. Prob or downer is low torque particularly at low rpm ,great exhaust note though .
TVR did it in the Cerbra V8 too .AJP Engine from memory?
Ferrari abandoned it in the 430 , 458 488 , went back to conventional “ pairs “ in order to get more low down torque or shift it to the left on the graph ,makes it more drivable .
Gets a bit tiresome working in the 6- 9000 rpm rev range .
Having said that some V8 ,s in the interest of smoothness may fire at 8 different times individually.
I know the Jag V12 had seperate pistons reaching TDC ,no pairs or groups of 3 in this case .Hence when you revved it up with a glass of water on it , there was not a ripple = super smooth , and torquey to boot .

Of course the exact firing order for MapishM s MAN diesel V8 will be in the manual ,I suspect they work in pairs one on each bank together = super smooth as in therory they balance each other .

Come to think of it they do major on crank dampers , or the MAN V 12 ,s do cos working in 3 ,s there’s an inherently prob of two on one side and one on t,other firing off together .

I,ll shut up waiting for MapishM to report back on his barring excursion

 

[Portofino]

On a more general subject relating to the desire / need to excerise the valve springs or indeed attempt to completely relax them ,which I think you can,t realistically do any way as explained above ,because without the covers off you can,t see if they are relaxed ,

can I ask what are you trying to prevent valve spring wise ? By barring the engine?

Reason I ask bear with me ,the limiting factor of rpm in a 4T is actually valve bounce .
This is when the spring can’t resrsit a rebound when a valve closes at the highest speed it can ,they start bouncing ,thus power losses.
In this case UN fatigued springs are desirable. , so even a small say 4 % of fatigue over say a 10 y life of 1000 hrs will result in potentially a valve bounce maybe starting .Loss of power @ higher rpms only and reduced ability to get up into that zone .
But and it’s a very big BUT this sort of power loss due to fatigued springs occurs right up at 8000 rpm + perhaps 9500 tops
That’s the zone we are talking about where valve springy ness needs to be spot on - as new so to speak .

But we are talking about an engine that “ only “ maxes out @ 2300 rpm , valves and the springs moving at a slough like pace , so even with a what ever % of lost springness ,you are never gonna see that .
It’s rarely gonna ever go over 2000 rpm .
Start a Ferrari up from cold it ticks over at 2000 rpm and settles to 1200 when warm ,
So @ tick over a Ferrari V 8 ,s valves are moving as fast as a MAN marine diesel V 8 cruising .
The MAN never sees 9000 rpm or needs springs ( and the rest of the valve train ) to cope with that .

There for a low revering 4 T engine , the lower the rev s from 9000 or (1200 in a bike ) - lests call it the bounce limit it is , the less need for valve excerise in a lay up .

A 2000 rpm er has got to be @ the right back of that Q .

That’s why your seasonal 4T powered garden equipment survives years and years of inactivity periods .
Once you sort the fueling out after a lay up runs as new .

 

[benjenbav]

My answers, predicated by the statement that I wouldn't: if the valve springs are not going to survive 7 months of static load then you might be looking at bigger issues.

1) Don't
2) Don't
3) Don't