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Old 21-07-2014, 08:22   #31
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Re: Adjusting Valve Clearances on a Diesel Engine

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Originally Posted by svlamorocha View Post
You made me realize that I lost my notes from when I took a course with Larry Berlin at Mack Boring class, which helped me do this job twice in my 3YM20. Here is some blurb that was posted in the Catalina 42 forum that is said to come from Larry Berlin and sounds similar to what I remember except that it is fo ra 4-cylinder engine.:

4JH2E Valve Adjustment Procedure in Archive-Engine-generator-diesel-ob-hoist Forum

I hope this helps for your 4JH.

In all Yanmars you started at TDC compression if cylinder closest to flywheel, which may or may not be #1 depending on the model.

The only thing that is missing here is the little table that shows you the sequence depending on the number of cylinders. There were three ways of finding the points where to stop turning to adjust the first set of valves. One was based on looking at marks in the flywheel, another one based on the midpoint of the range in which the valves are closed (adjust that valve) and another one looking at the "overlap" of valves (adjust valves un cylinder X when cylinder Y is in overlap). Hopefully someone can shed light as to whether those three recipes always give you the same result. Or maybe the right recipe depended on the # of cylinders, which would made sense. All that said, I do recall it was quite obvious what to do once you turned the engine a couple of times.

Do not worry about decompression. A socket with a bar on the flywheel nut will do if you go slow.
Very useful. So I guess I'm going to go with that.

It's just like doing a petrol engine. Except you don't relieve the compression; you just brute force it.

You loosen the injection pipes so that the engine doesn't (God forbid) start.

You can look for valve overlap at the opposite cylinder to get TDC power stroke for the cylinder you're adjusting.

Yanmar clearances are cold.

Seems quite straightforward.
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Old 21-07-2014, 09:46   #32
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Re: Adjusting Valve Clearances on a Diesel Engine

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Originally Posted by Dockhead View Post
You loosen the injection pipes so that the engine doesn't (God forbid) start.
You can also pull the stop cable or lever out if you have one.

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Old 21-07-2014, 10:27   #33
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Re: Adjusting Valve Clearances on a Diesel Engine

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Originally Posted by Ex-Calif View Post
Not sure why everyone has an aversion reading the manual for their engine instead of getting guesses from here - LOL.

The exhaust and intake strokes may overlap. In fact they probably do - RTFM.

I don't know what you mean by a wider flat spot - there is only one cam lobe per valve. The known position with both valves closed is the top of the compression stroke but this is probably not where your manual wants you to adjust the valve clearance.

Both valves are closed from just before BDC on intake until just before BDC on power stroke - almost one revolution.

The reason many manuals want you to locate a particular stroke is they may also be instruction you to check for valve lash - Valve lash is an indication of cam lobe wear.

e.g. after adjusting to a .020 valve clearance the manual will tell you that this intake valve should start opening at X deg before TDC - if it is late, it is because the cam lobe is worn. It should close Y deg before after BDC if it is early it is because cam lobe is worn.

Clearly if the intake valve opens late and closes early, you get less fuel/air charge.

BTW - Remove the injectors when doing a valve clearance adjustment - If you adjust valves at 1,000 hours isn't it time to take a look at your injectors?

Also be very careful using the starter to "bump" the engine. On a gasoline engine you remove the coil wire - On a diesel engine it could start!

Valve adjustment time is the time to do a full service on the engine - fluids, injector inspection, filters etc.

No need to take a short cut by not removing the injectors here.

PS - I haven't seen one for small diesels but you can buy a tool. It is a pointer that screws into the port. As the piston comes up and contacts it, it deflects to a card pointer. You rotate the engine back and forth to find TDC on cylinder 1 - half way between two known deflections. There is a degree wheel you then attach to the flywheel so you can measure the crank angle.
"wider flat spot" One lobe per valve, two lobes, but these lobes are not 180 degrees apart right? What I meant (right or wrong!) was the "back" side of the cam rotationally away from both lobe peaks.
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Old 21-07-2014, 10:42   #34
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Re: Adjusting Valve Clearances on a Diesel Engine

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Originally Posted by delmarrey View Post
Heck, in my old gear jam'n days we use to put clips over the rocker squirter hole and adjust them with the motor running. But I guess on a boat one could get sucked up in a moving part as cramped as some boat motors are. Or oil would be running off the back, with the angle of some motors.

Anyway, cams now days are computer ground for special applications, like torque or RPMs so having the lobe at the right angle when adjusting could be important. That's why I would stick with the manufactures recommendations rather then a farmers guess.
I always adjust the clearances on my present Westerbeke W46 with the engine idling. Was taught how to do it 50+ yrs ago.
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Old 21-07-2014, 11:11   #35
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Re: Adjusting Valve Clearances on a Diesel Engine

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I always adjust the clearances on my present Westerbeke W46 with the engine idling. Was taught how to do it 50+ yrs ago.
Most likely I assume hydraulic lifters? Idea being to get them in the center of their automatic adjust-ability range, loosen them until it begins to tick, then in a half a turn or so?
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Old 21-07-2014, 11:21   #36
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Re: Adjusting Valve Clearances on a Diesel Engine

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Most likely I assume hydraulic lifters? Idea being to get them in the center of their automatic adjust-ability range, loosen them until it begins to tick, then in a half a turn or so?
Actually With hard lifters. Learned to adjust the valves with the engine running from my dad, on his then newer Volvo PV544. Was only a bit messy Of course engine compartments in cars had better access back then too.

BTW you don't want to do that on a boats engine, adjust when running. Oil goes everywhere...
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Old 21-07-2014, 11:22   #37
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Re: Adjusting Valve Clearances on a Diesel Engine

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Originally Posted by Blue Stocking View Post
I always adjust the clearances on my present Westerbeke W46 with the engine idling. Was taught how to do it 50+ yrs ago.
Yeah, on gas engines I always did that too. (solid lifters) My diesels flung too much oil for that!
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Old 21-07-2014, 12:32   #38
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Re: Adjusting Valve Clearances on a Diesel Engine

Used something called "slopper stoppers" or similar such name on GM Hydraulic lifters to keep the oil from squirting out.
Never seen a solid lifter, or roller adjusted on a running engine though
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Old 21-07-2014, 15:21   #39
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Re: Adjusting Valve Clearances on a Diesel Engine

I find the firing sequences and the cams with the degrees around the shaft with the turns interesting, but excess to the simplicity of adjusting each valve by convenience as you see it rise and fall. Then easily turn the flywheel to locate the TDC for adjustment. Why attempt to adjust the valves in a specific sequence? 'just run through the revolution of the flywheel and adjust them as they present themselves and record their completion so none are missed. Why not?
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Old 21-07-2014, 16:19   #40
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Re: Adjusting Valve Clearances on a Diesel Engine

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I find the firing sequences and the cams with the degrees around the shaft with the turns interesting, but excess to the simplicity of adjusting each valve by convenience as you see it rise and fall. Then easily turn the flywheel to locate the TDC for adjustment. Why attempt to adjust the valves in a specific sequence? 'just run through the revolution of the flywheel and adjust them as they present themselves and record their completion so none are missed. Why not?
yep
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Old 21-07-2014, 17:09   #41
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Re: Adjusting Valve Clearances on a Diesel Engine

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Originally Posted by Blue Stocking View Post
I always adjust the clearances on my present Westerbeke W46 with the engine idling. Was taught how to do it 50+ yrs ago.
It's a method that works well on a warm engine but it beats the **** out of your feeler guage over time. I do mine one cyl. at a time cold and recheck after spinning the engine on starter only and if it stays within + or _ .001 its good to go.
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Old 21-07-2014, 17:39   #42
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Re: Adjusting Valve Clearances on a Diesel Engine

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I've not found the need to relieve compression. You can turn them very slowly to where you need to be. IF I remember right watch for the exhaust valve to be depressed and back up and before the intake goes down. There's your adjustment spot. Someone please refine this for me...with more detail...
Rock the crank back and forth and feel for movement on both rockers and adjust.
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Old 21-07-2014, 17:45   #43
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Re: Adjusting Valve Clearances on a Diesel Engine

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Originally Posted by Dockhead View Post
Very useful. So I guess I'm going to go with that.

It's just like doing a petrol engine. Except you don't relieve the compression; you just brute force it.

You loosen the injection pipes so that the engine doesn't (God forbid) start.

You can look for valve overlap at the opposite cylinder to get TDC power stroke for the cylinder you're adjusting.

Yanmar clearances are cold.

Seems quite straightforward.
Unless the engine is hot you can bar it over slowly with little danger of it starting. Loosening the injector lines prevents build of raw fuel in the cylinders as you bar it over. It makes for a less smoky restart.
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Old 21-07-2014, 17:47   #44
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Re: Adjusting Valve Clearances on a Diesel Engine

watch this video, it helped me learn how to do it on mine:

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Old 21-07-2014, 18:23   #45
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Re: Adjusting Valve Clearances on a Diesel Engine

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Originally Posted by perchance View Post
It's a method that works well on a warm engine but it beats the **** out of your feeler guage over time. I do mine one cyl. at a time cold and recheck after spinning the engine on starter only and if it stays within + or _ .001 its good to go.
True. The W46 are adjusted cold.
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