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Old 01-15-2021, 10:14 AM   #1
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Adjusting Valves on Perkins 4.108

Several days ago I decided to adjust the valves on my Perkins powered generator. I always suspected that it had been a very long time, if ever, that they had been adjusted. The engine has 2,550 hours on it. Removing the valve cover was easy. Removing the cork gasket, not so much. Based on how hard the gasket was I am now reasonably certain that the valves had never been adjusted. I had to use a wire wheel on a die grinder to remove the gasket,

On to the adjusting. I checked the lash before adjusting each valve, I was not able to insert a .005 feeler gauge into the space on any of the valves. The spec is .012 for both the intake and exhaust. My guess is that the lash was about .003 before adjustment.

Adjusting the valves was quite easy. New cork gasket and I was ready to go. I can report that this engine runs a lot more smoothly and quieter. Beforehand, there was a lot of clattering which doesn't make me feel good. Clattering all gone.

I posted this experience as I am guessing that many boaters, including I, don't think about adjusting their engine valves. I adjusted my two Lehmans last year and had the same experience, smoother and quieter. A word to the wise so to speak.

Also, a big thanks goes to Ski In NC. Ski taught me how to adjust the running speed. Because of governor sag due probably to age, the generator end was not spinning fast enough to produce juice at or near 60Hz. It was 57.5Hz. As I write this I have my generator loaded up with two reverse cycle A/Cs, and two resistance heaters. It's 42 degrees at 10:10am on the Chesapeake. Anyway, the generator is putting out a steady 59.7Hz, about as good as one could wish.

So, here you go, another project for your to-do lists.
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Old 01-16-2021, 07:55 AM   #2
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"I can report that this engine runs a lot more smoothly and quieter. Beforehand, there was a lot of clattering which doesn't make me feel good. Clattering all gone"

With too small clearance the lifters can not use the take up ramp built on the cam lobes , so the valve is whacked open rather than lifted , so is quieter now that the adjustment is proper.
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Old 01-16-2021, 01:31 PM   #3
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The lifter will follow the cam's profile including the ramp regardless of how the valves are adjusted. If anything, the lifter is actually held more closely to the profile.

What can, and likely does happen when there isn't enough valve lash, is that as the engine warms, the valve train expands and the lash goes away completely, and then the valves start leaking.

It's the explosive gases sneaking past the valves that creates the noise and poor engine performance or worse.

The reason valves need maintenance in the first place is that the valve and it's seat naturally wear away. Given that my rule of thumb is always to stay on the loose side. For your engine Catalina Jack with a spec of .012, for me that would mean never tighter than .012, at .011 I'd always re-adjust.
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Old 01-16-2021, 03:22 PM   #4
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FF you are correct that valve adjustment can cause the valves to be opened with a whack, it just happens when the valve gets too loose. The lifter still follows the cam profile but there is lots of slack between there and the valve stem so the valve train is moving pretty quick when things finally touch, in this case that touch is more like a hammer blow, and yes it’s noisy and the engine runs poorly to.

The lash needs to be significant for that to happen. Typically ‘too loose’ only happens when a lock nut comes loose and the adjuster backs off.
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Old 01-16-2021, 03:53 PM   #5
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Mark, thanks so much for the education. Obviously, .003 valve lash is not good. I should have adjusted those valves 200 hours ago when we first got the boat. I will check the lash again after another 100 hours of operation.



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The lifter will follow the cam's profile including the ramp regardless of how the valves are adjusted. If anything, the lifter is actually held more closely to the profile.

What can, and likely does happen when there isn't enough valve lash, is that as the engine warms, the valve train expands and the lash goes away completely, and then the valves start leaking.

It's the explosive gases sneaking past the valves that creates the noise and poor engine performance or worse.

The reason valves need maintenance in the first place is that the valve and it's seat naturally wear away. Given that my rule of thumb is always to stay on the loose side. For your engine Catalina Jack with a spec of .012, for me that would mean never tighter than .012, at .011 I'd always re-adjust.
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Old 01-19-2021, 07:13 AM   #6
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The valve adjustment depends on the "feel" , the drag on the feeler gauge, which changes from country to country.

The Germans prefer high drag , in other countrys , not s much.

The easiest way to be close enough is the GO - No GO method.

If say .012 is needed a .011 feeler should slide easily with minimum drag and a .013 would be a very hard force fit .

You are pushing against a spring so there is no limit to what can be forced in , be reasonable.

Be sure to check again after securing the locking nuts .

Some manuals give a great procedure for a proper adjustment to assure the cam is in the proper position (not lifting a valve).

They will specify a cylinder and its valve position as open , at which time you can adjust both intake and exhaust on the cylinder you are working on.

Enjoy!
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Old 01-19-2021, 08:31 AM   #7
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I used the medium drag method. After adjusting, I rotated the engine through the process again to verify the new tolerances. On one pair of valves I found my adjustment to be slightly off. Corrected it, ran through again to re-verfy. All is well now.

I do think this is an important maintenance item but is often neglected.
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The valve adjustment depends on the "feel" , the drag on the feeler gauge, which changes from country to country.

The Germans prefer high drag , in other countrys , not s much.

The easiest way to be close enough is the GO - No GO method.

If say .012 is needed a .011 feeler should slide easily with minimum drag and a .013 would be a very hard force fit .

You are pushing against a spring so there is no limit to what can be forced in , be reasonable.

Be sure to check again after securing the locking nuts .

Some manuals give a great procedure for a proper adjustment to assure the cam is in the proper position (not lifting a valve).

They will specify a cylinder and its valve position as open , at which time you can adjust both intake and exhaust on the cylinder you are working on.

Enjoy!
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Old 01-19-2021, 10:23 AM   #8
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I had a valve problem on one of my sailboats. If I pushed the little raw water cooled engine too hard it would make a top end knock that sounded like it was coming apart. If I backed down it would cool a little and the noise would stop. Turned out the lash on both exhaust valves was 0 and that little extra heat would make them expand enough to leak. Engine was 30 something years old with no hour meter so no idea how many hours it had, but I'd bet they'd never been checked. As I recall the gasket was rubber so no problem getting it off and I even reused it. No leaks after so I just left it that way. My new to me trawler has Perkins 6.354's only 600 hours so I don't think they need adjustment yet but it's on my watch list. Not happy to hear about the cork gaskets, I hate those things.
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Old 01-19-2021, 11:34 AM   #9
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You may find that the Perkins manual recommends adjustment after a certain number of hours after new. True for Lehman. If true for Perkins, do you have maintenance records that show it has been done? Something to think about?
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I had a valve problem on one of my sailboats. If I pushed the little raw water cooled engine too hard it would make a top end knock that sounded like it was coming apart. If I backed down it would cool a little and the noise would stop. Turned out the lash on both exhaust valves was 0 and that little extra heat would make them expand enough to leak. Engine was 30 something years old with no hour meter so no idea how many hours it had, but I'd bet they'd never been checked. As I recall the gasket was rubber so no problem getting it off and I even reused it. No leaks after so I just left it that way. My new to me trawler has Perkins 6.354's only 600 hours so I don't think they need adjustment yet but it's on my watch list. Not happy to hear about the cork gaskets, I hate those things.
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Old 01-19-2021, 11:37 AM   #10
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Yeah, if those cork gaskets were glued on with something like Permmatex #2, you will never be able to scrape of the old dried gasket. Every bit of old gasket must be removed to ensure a good seal. You will hate yourself if you don't do a complete job.
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I had a valve problem on one of my sailboats. If I pushed the little raw water cooled engine too hard it would make a top end knock that sounded like it was coming apart. If I backed down it would cool a little and the noise would stop. Turned out the lash on both exhaust valves was 0 and that little extra heat would make them expand enough to leak. Engine was 30 something years old with no hour meter so no idea how many hours it had, but I'd bet they'd never been checked. As I recall the gasket was rubber so no problem getting it off and I even reused it. No leaks after so I just left it that way. My new to me trawler has Perkins 6.354's only 600 hours so I don't think they need adjustment yet but it's on my watch list. Not happy to hear about the cork gaskets, I hate those things.
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Old 01-19-2021, 11:45 AM   #11
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That's why I hate them. BTDT.
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Old 01-19-2021, 11:53 AM   #12
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Quote:
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You may find that the Perkins manual recommends adjustment after a certain number of hours after new. True for Lehman. If true for Perkins, do you have maintenance records that show it has been done? Something to think about?
Book says to check at the first 25-50 hours then every 2400 thereafter. No records so unknown if was done on break in. It's a 1973 model so 50 hours was a long, long time ago by the calendar. It's on the to do list but not at the top.
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Old 01-20-2021, 07:27 AM   #13
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"Book says to check at the first 25-50 hours then every 2400 thereafter."

The valve face and valve seat are ground at a slightly different angle when new or rebuilt..

After running they will have seated to each other , so only one adjustment at low hours is needed.
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