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Old 13-07-2020, 19:15   #1
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valve springs

Hello,
I have a Volvo Penta MD2B; I'm not sure how much use it has had, but likely hasn't been in use for ~30 years.
In looking at the valve springs, their unloaded height is ~48mm (technical data lists 50mm). Would they be worth replacing? I can't find any standards on how much they can be off. I also haven't checked loaded height. I can't seem to find consensus on the life of a spring, even if it isn't being used. Anything rubber on this engine is close to dust and requires replacing but I'm not sure what to think about in terms of the springs. Anyone with experience or knows what's the average life expectance of a spring I would appreciate hearing your views.

Thanks
Jeremy
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Old 13-07-2020, 21:23   #2
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Re: valve springs

At 30 years with little to no use Iíd replace them. Iíd worry about cracking a spring and dropping a valve.
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Old 13-07-2020, 21:49   #3
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Re: valve springs

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At 30 years with little to no use Iíd replace them. Iíd worry about cracking a spring and dropping a valve.
Can you explain this to me? I'd think that spring steel would just be fine sitting for any length of time. Our Kubota based engine is now 32 years of age and the original springs are still working as normal.

And FWIW, considering the rpm that these engines run at, valve springs have a pretty unstressed life -- valve float isn't much concern. (This is a completely unprofessional opinion, based on ancient experience with hot-rodded petrol engines running far over their design speeds).

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Old 13-07-2020, 22:15   #4
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Re: valve springs

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Can you explain this to me? I'd think that spring steel would just be fine sitting for any length of time. Our Kubota based engine is now 32 years of age and the original springs are still working as normal.

And FWIW, considering the rpm that these engines run at, valve springs have a pretty unstressed life -- valve float isn't much concern. (This is a completely unprofessional opinion, based on ancient experience with hot-rodded petrol engines running far over their design speeds).

Jim
Itís been sitting mostly if not completely unused for 30 years, steel rusts and can become brittle. Springs are cheap and sounds like itís apart or partially apart already. Two very different animals with a well used 32 year old engine and one sitting untouched for the same period.
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Old 13-07-2020, 22:15   #5
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Re: valve springs

Our engine is a 1980 model & we are still using the original springs. My guess is that you will be fine. If you are truly worried put a 2mm spacer under the spring .Assuming it isnt rusty
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Old 13-07-2020, 22:28   #6
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Re: valve springs

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steel rusts and can become brittle.
Agree on the possibility of rust, but that is easily inspected. Just how would the steel become brittle? That does not seem likely to me, but I'm no metallurgist.

Jim
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Old 13-07-2020, 23:41   #7
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Re: valve springs

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Agree on the possibility of rust, but that is easily inspected. Just how would the steel become brittle? That does not seem likely to me, but I'm no metallurgist.

Jim
Depends on the alloy and the environment. 30 years of sitting dry exposed to salt air; or just swap them out for a couple hundred bucks and avoid destroying a cylinder. Iíd also be checking them for square. Big point is it sounds like he has the springs on the table, that means the headís off on an unknown engine, nows not the time to cut corners.
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Old 14-07-2020, 13:35   #8
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Re: valve springs

Usually, if an automotive head is rebuilt, shims are placed under the springs. If you're taking the engine apart to replace the seals, I'd replace the valve seals, shim the springs and probably replace the rings.
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Old 14-07-2020, 15:01   #9
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Re: valve springs

Steel can become brittle by overheat treating and hydrogen embrittlement, for instance you should never use paint stripper on spring steel landing gear,
But I hope age or sitting doesn’t affect spring steel, or my 1946 airplane will surely be sitting on its side.
However if they don’t meet spec, I’d replace them, unless they have a Volvo price on them, which they may.
Valve float just won’t be an issue, that comes from radical cam profiles and high RPM, neither of which we have in our baby Diesels.
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Old 14-07-2020, 21:07   #10
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Re: valve springs

Hello,
Yes, the engine is apart so it wouldnít be a bad time to replace them but they are Volvo springs with a Volvo price..
I did check them for square and they seem off a bit and the two springs are different In colour so Iím assuming at least one of them was replaced before.
The engine (as far as I know) wasnít around salt water and there isnít any rust, thee fine is in rather good shape besides everything rubber falling apart.
I appreciate everyoneís input so thanks for taking the time to give some advice. Has anyone come across a broken spring or any issues bc of old springs?

Thanks
Jeremy
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Old 15-07-2020, 00:02   #11
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Re: valve springs

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Originally Posted by shoeless View Post
Hello,
Yes, the engine is apart so it wouldnít be a bad time to replace them but they are Volvo springs with a Volvo price..
I did check them for square and they seem off a bit and the two springs are different In colour so Iím assuming at least one of them was replaced before.
The engine (as far as I know) wasnít around salt water and there isnít any rust, thee fine is in rather good shape besides everything rubber falling apart.
I appreciate everyoneís input so thanks for taking the time to give some advice. Has anyone come across a broken spring or any issues bc of old springs?

Thanks
Jeremy
Springs wear out and do break occasionally. If theyíre out of square more than 1/32 replace them. If theyíre square and want to reuse them pull each corresponding valve and check valve/seats for any visible pitting carbon etc. If one looks noticeably bad replace that spring and lap or reseat the valve. Chances are if theyíre square the valves will be fine though.
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Old 15-07-2020, 01:27   #12
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Re: valve springs

At 35 euros a pop, I'd be seriously considering reusing them. Volvo manual

https://www.manualslib.com/manual/10...page=42#manual

says nothing about squareness, so unless they're extremely out-of-square, wouldn't worry about that either. Specs from the book are below, a good head shop should have a load tester, only if they seriously deviate from the length under the listed load would I worry about them.

Of course, if you can get them for the 3-4 dollars they should cost, by all means replace them as a matter of course. There may be an aftermarket supplier, or there could be a valve from another engine that will work.
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Old 15-07-2020, 01:46   #13
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Re: valve springs

What do you expect from the engine when you finish? That it will be like new and good for another 30 years? Or are you ok with just getting into good serviceable condition again, and don't mind too much the prospect that it might have to come out again for something in a few years.


I think that's the threshhold question. When the engine is easily removed and disassembled and especially if you even enjoy tinkering with it, that's one thing.


My engine is so hard to get out, requiring the removal of cockpit floor and heavy duty generator, that if I were ever to have it out, I would replace all conceivable wear parts to make it as close to "good as new; totally rebuilt" as possible. In fact once I go to that trouble and expense, I might actually just repower with a new engine.


This is also something to think about. But if it were me, I wouldn't much like reusing valve springs which are measurably out of spec, and especially if they vary by color. YMMV. I had a new old stock clutch pressure plate I installed in one of my Porsche 911's, shatter. It had only the slightest bit of surface rust on it. I would replace with extreme prejudice ANY internal engine part, with any visible surface rust on it.
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Old 16-07-2020, 15:09   #14
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Re: valve springs

Reject the spring if there is ANY pitting on it. Reject if more than .080" out of square. As long as they have about 80-90 lbs pressure at installed height they should be OK. F=kX where F is newtons (388N to 400N= 80-90 lbs) and X in meters.

I would be careful of shimming especially at 2mm. If you have a bind space of .060" or more at full lift you should be OK.



Aftermarket springs can be had from spring suppliers by dimension. They are not big/heavy valves and anything that installs at 80-90 pounds at installed height, free bind of .100" or more and max height bind of .060" should be fine. It's not like you are spinning the engine at 10000 RPM. Max is about 3200 for that engine.
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Old 16-07-2020, 19:01   #15
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Re: valve springs

Just to clarify some things:
1. Steel does NOT degrade with age. The age of the springs is irrelevant. A spring made 100 years ago will have the same properties today as it had when manufactured, if it has not been used and has not been degraded by corrosion or exposure to hydrogen as others have noted.
2. Corrosion caused pitting on the spring will guarantee that it will fail. The pits on the spring caused by corrosion will act as stress concentration points and this will cause failure, not immediately, but after the engine has run for awhile.
3. The volvo manual should spec how much settling (meaning reduction in spring length) is acceptable.

If they're in spec for length and are not corroded they're fine. Use them.

If they're corroded or are under the minimum length spec you should replace them. If they're only a little under the minimum length spec I'd still use them, but if significantly under the minimum you may not have enough spring force to control the valve at high RPMs.
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