Valve adjust on LD28

Discuss (and cuss) the Nissan LD-series OHC Six diesel engine, popularly available in the US in 1981-83 Datsun/Nissan Maxima Sedans & Wagons.

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glenlloyd
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Valve adjust on LD28

#1

Post by glenlloyd » 14 years ago

Hey all
So at 154k miles I thought it would be good to check and adjust the valves. I hauled the book out, pulled the valve cover, lined up the cam properly and began checking the clearance. Funny thing is however, they were all about .02 off the mark, too tight. Engine was hot too, so that shouldn't have been an issue.

The intake are supposed to be .010 and exhaust were supposed to be .012, but the intake valves were all about .007-.008 and the exhaust were all right at .010. So, not wanting to make a mess of it, I left them all alone for now.

If anyone can shed some light on this one please do so. Is the book wrong or should I change them all to what the FSM says?

Thanks
Steve A
97 Jetta TDI, 86 VW Golf D
89 VW Fox diesel, 92 MB 300SD W140

gir - won't the sploding hurt?
zim - silence!

Dr. Jones
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Valves

#2

Post by Dr. Jones » 14 years ago

I'm thinking just did about the same thing I was going to adjust them but I didn't have the right tools and couldn't do it properly and I left it alone. The more I use the book('82 FSM 810) the more I trust it. I saw your other post on why they call it a 910 everywhere else and that what started into thinking that some its information might be wrong.
'82 Maxima Sedan x2
'92 Saab 9000 Griffin Edition Wrecked
'80 Ford E100(twisted tranny) SCRAPPED

glenlloyd
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Re: Valves

#3

Post by glenlloyd » 14 years ago

Dr. Jones wrote:I'm thinking just did about the same thing I was going to adjust them but I didn't have the right tools and couldn't do it properly and I left it alone. The more I use the book('82 FSM 810) the more I trust it. I saw your other post on why they call it a 910 everywhere else and that what started into thinking that some its information might be wrong.
I think the 810/910 issue is perhaps a coutry specific thing. I know in Australia ou 810/Maxima is referred to as the Bluebird/910, other places as well. I do however, think that the FSM is really reliable, much more so than even the Bentley manuals I use for the my VW's. The Datsun FSM is a really comprehensive and thorough manaul. Now that I have it I wouldn't be without it actually.

my. 02

Steve Addy
97 Jetta TDI, 86 VW Golf D
89 VW Fox diesel, 92 MB 300SD W140

gir - won't the sploding hurt?
zim - silence!

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asavage
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Re: Valves

#4

Post by asavage » 14 years ago

I think the Maxima in Canada was marketted as a 910. I think.
glenlloyd wrote:The Datsun FSM is a really comprehensive and thorough manaul. Now that I have it I wouldn't be without it actually.
And they're so cheap to buy, used. For those reading this who don't have the Factory Service Manual yet, use the canned "eBay Search" link under the Service Information section of the FAQ.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

diesel-man
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Location: Elkton, MD

#5

Post by diesel-man » 14 years ago

I find that after the valves are adjusted, that they are good for like 75K. Almost every car I have checked seems like I "got" it just in time. I think it is the second valve from the front is a little hard to get loose, so I push the valve down with a large screwdriver and remove the "cam follower" (rocker arm) and use a socket to loosen the adjuster. All of the others can be loosened with a short 17MM wrench.
I have found it is the exhaust valves that get tight. In a perfect world, tight valves give more lift on the cam, but zero clearance is the beginning of a burnt valve. :cry:

goglio704
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#6

Post by goglio704 » 14 years ago

Why would a valve get tighter as it ran? I can see some variation from one check to another due to temperature. But if I understand what you are saying correctly, the valves will progressively tighten until they no longer seat, leak, and burn? Does the mating surface of the valve and seat erode that much in the course of 75K miles? That is the only source of tightening that I can see. If it happens it happens, but it seems a little counter intuitive to me. I guess when I think about it though I have never owned a vehicle with a non-hydraulic valvetrain long enough to see a pattern emerge. If tightening is the normal progression, that makes for a real good motivator to do valve maintenance sooner rather than later.
Matt B.

83 Maxima Sedan, LD28, 5 speed, white, 130k miles. My original Maxima.
83 Maxima Sedan converted from gasser, LD28, 5 speed, 2 tone blue, 230k miles
82 Maxima Sedan, LD28, 3 speed auto, 2 tone Gray/Silver, 140k miles
81 810 Sedan, LD28, 3 speed auto, rust, rust, and more rust!

2005 Jeep Liberty CRD

diesel-man
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Location: Elkton, MD

#7

Post by diesel-man » 14 years ago

The valve face and seat face actually wear because the valves are opening and closing at such a speed (valve spring pressure) that it is somewhat like a hammer against a piece of steel. I don't know what the valve lift is off-hand, but I would guess it is about 3/8" so it isn't as if you get a lot of momentum going, but after 100K it makes a difference. I'm only 45, but to adjust the valves on a flathead Ford V-8 you grind a little off of the end of the valve to create clearance. A Chevette uses flat shims under the lifter cap which rides under the cam. (overhead cam) Since it is not such a difficult job on a Maxi that it is unreasonable, like these two examples, it is just cheaper to know what "you are riding on".

When the gas guage is broke and you are almost out of gas it does not foster worry. :shock: It had enough gas yesterday...it will have enough tomorrow. Ignorance (of your problem) is bliss!

goglio704
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#8

Post by goglio704 » 14 years ago

Everybody is ignorant of something. Only fools are afraid to ask questions.
Matt B.

83 Maxima Sedan, LD28, 5 speed, white, 130k miles. My original Maxima.
83 Maxima Sedan converted from gasser, LD28, 5 speed, 2 tone blue, 230k miles
82 Maxima Sedan, LD28, 3 speed auto, 2 tone Gray/Silver, 140k miles
81 810 Sedan, LD28, 3 speed auto, rust, rust, and more rust!

2005 Jeep Liberty CRD

diesel-man
Posts: 150
Joined: 14 years ago
Location: Elkton, MD

#9

Post by diesel-man » 14 years ago

Didn't mean that.

I repair cars everyday, and you just don't know how many cars I pull the dipstick on, and there is nothing showing. (people should brush their teeth before going to the dentist). People drop their car off with the gas guage on E and ask me to try it out, to diagnose their problem (can damage the fuel pump in the tank by running that low on fuel)(fuel pump is cooled by the gas). People ask if their car will be ok on a trip. Too many parts on a car to catch each one before it lets go. But if you do all you know to do, go on a trip and something happens, at least you can be on the same side of the fence as your other passengers...who knew?

It is just as I said, it is just cheaper to know what you are riding on. If the valves have never been checked since you have had it, it would be a couple hours well spent to know. Also put a new valve cover gasket on it. (rubber gasket gets hard from heat and starts to leak) As on another post, the injection pump belt if you are going on a trip. I had a belt go at about 100K, but I only drive back and forth to work with my maxi, I use a Dodge diesel truck for vacation trips. Chances are the engine will outlast the body on most Maxima's unless it is Southern states away from the seashore.

Not trying to be inflamatory at all. The "your" in (Ignorance (of your problem) is bliss!) is the same word for the singular and plural version of that word. I don't even know you that well, this is my first "day" on this site..... The last paragraph in my post is more like a message to the "crowd" not the person on the front row. ????Sorry

Dr. Jones
Posts: 125
Joined: 14 years ago
Location: Raleigh NC

#10

Post by Dr. Jones » 14 years ago

Welcome, diesel-man. I think we have a record for online at once.
Last edited by Dr. Jones 14 years ago, edited 1 time in total.
'82 Maxima Sedan x2
'92 Saab 9000 Griffin Edition Wrecked
'80 Ford E100(twisted tranny) SCRAPPED

goglio704
Posts: 726
Joined: 14 years ago
Location: East Tennessee

#11

Post by goglio704 » 14 years ago

Nothing to be sorry for. Sorry if I was thin skinned. Welcome to the forum.
Matt B.

83 Maxima Sedan, LD28, 5 speed, white, 130k miles. My original Maxima.
83 Maxima Sedan converted from gasser, LD28, 5 speed, 2 tone blue, 230k miles
82 Maxima Sedan, LD28, 3 speed auto, 2 tone Gray/Silver, 140k miles
81 810 Sedan, LD28, 3 speed auto, rust, rust, and more rust!

2005 Jeep Liberty CRD

glenlloyd
Posts: 640
Joined: 14 years ago
Location: Des Moines, Iowa
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#12

Post by glenlloyd » 14 years ago

diesel-man wrote:I have found it is the exhaust valves that get tight. In a perfect world, tight valves give more lift on the cam, but zero clearance is the beginning of a burnt valve. :cry:
So...it wasn't just coincidence that I couldn't get the feeler gauge in there? They actually do get tighter? So in my case where the correct feeler gauge wouldn't fit in there I should go ahead and change them?

Thanks
SA
97 Jetta TDI, 86 VW Golf D
89 VW Fox diesel, 92 MB 300SD W140

gir - won't the sploding hurt?
zim - silence!

diesel-man
Posts: 150
Joined: 14 years ago
Location: Elkton, MD

#13

Post by diesel-man » 14 years ago

This is correct. With the cam overtop it is the natural progression for the valves to tighten. On a overhead valve setup it is more likely that the lifter, pushrod and rocker arm would wear at a greater rate than the valve/seat. Since the Camshaft and cam follower (like a rocker arm) are so hard (they won't wear like a GM camshaft form the 60's thru 80's) the valve and seat wears and tightens the clearance. I totally understand if you check them and they are .008 & .010 and it would seem like it is too much trouble to adjust them. ('cause it is) but I only check them at about 75K or when it comes to my attention. (valve cover leaking, or if I remember what mileage it was when I got that one.)

I just recommend to everyone, if you don't have a good idea when it was done, to find out. This isn't a weak point or anything, but all these cars are old enough to vote +

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asavage
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#14

Post by asavage » 14 years ago

goglio704 wrote:Why would a valve get tighter as it ran?
Happens. History lesson follows.
Matt, the following isn't WRT the LD28, but it's good to know anyway.

Most American engines pre-80s had cast-iron heads (leaving out things like Corvairs, etc.). For cost reasons, the valve seating areas of cast iron heads are generally . . . cast iron. With lead as a fuel additive, this worked rather well. Early on, there were problems with carbon accumulating on the valve face and valve seat, which would create leakage, reduce heat transfer from the hot valve head to the cool valve seat, and led to burnt valves and damaged seats. Because this was a larger problem with (hotter) exhaust valves than intake valves, the "solution" was generally applied only to exhaust valves: valve rotators were installed to rotate the valve slightly every time the valve was opened. They install at the top of each exhaust valve spring.

The rotators helped prevent carbon from building up on the valve's face, but they also increased valve and seat wear. Various solutions were proposed, but mostly the valves got upgraded to tougher material, and the cast iron valve seats got rudimentary induction hardening -- a cheap method to make cast iron a bit tougher.

Automatic lash adjusting systems (ie hydraulic valve lifters) that compensate for thermal expansion and valvetrain wear, masked valve seat wear well for many years. By the time you had burnt valves, you were well out of the mfgr's warranty, the only real metric of a successful design ;)

That brings us to 1975, the widespread introduction of catalytic converters in the US, and low-lead and lead-free fuel. Getting the lead out was a very good idea -- Google "tetraethyl lead" and learn more if you want -- but it was a huge problem for valves and seats. Lead functioned as a anti-scuff lubricant at the high temps at which exhaust valves operate, and without lead (and with valve rotators), chunks of the seat could actually weld to the valve and tear out in certain conditions. Incidence of burnt valves & burnt seats rose considerably during this period. Heat transfer from exhaust valve to head was also hampered by higher coolant temps demanded by emissions stds of the day and carburetor technology.

Burnt valves were in their heyday.

Gradually, everyone moved to hardened valve seats throughout the industry. Aluminum alloy head engines always had them, so most foreign cars didn't suffer increased valve/seat wear in the '75-85 timeframe.

For a long time after the phase-out of lead, older cars continued to suffer valve problems, but now a new twist arose: valve seats were wearing so badly that the valves were actually recessing into the head. Automatic lash adjusters would compensate to a point, but with the valves shrouded/pocketed, even at full lift there wasn't enough room to get the air/fuel mixture by the valve and into the combustion chamber.

The fix is a more expensive valve job, one in which the cast iron heads are retrofitted with hardened valve seats. This is where we are today WRT older heads and valves. If you have to pull a head for valve work, on a gasser you pretty much have to have a machine shop install new valve seats, or run a lead additive all the time. Oh, and the valves will usually have to be replaced too. And often the valve guides.

For a long time, I did a pretty good business doing this kind of thing. The demand has tapered off greatly because there aren't a lot of people willing to spend $6-1200 on a valve job for a 25 yr old car/truck these days, but if you buy an old iron head pre-80 gasser rig, it's in your future.

Nowadays, burnt valves are fairly uncommon. In our small (5 bay) shop, I saw exactly three burnt valves in three years. But blown head gaskets, they're the new Black . . . er, I mean the replacement common problem for burnt valves. Head gasket failure is very common (and more common on certain rigs, Ford 3.8l, Subaru all, older Honda, etc.).

Diesels don't seem to suffer from the phase-out of lead in gasoline ;) However, we've got our own problems RE the declining lubricity of our diesel fuel, due to refining process changes, and again fuel additives can come to the rescue. PowerService, SeaFoam, Stanadyne fuel treatment, and biodiesel can all restore lubricity to our fuel.

Hope this wasn't too boring. It just happens to be a topic I know fairly well.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

goglio704
Posts: 726
Joined: 14 years ago
Location: East Tennessee

#15

Post by goglio704 » 14 years ago

Do you think fuel lubricity in a diesel will impact valve seat wear? Big believer in Stanadyne conditioner by the way.
Matt B.

83 Maxima Sedan, LD28, 5 speed, white, 130k miles. My original Maxima.
83 Maxima Sedan converted from gasser, LD28, 5 speed, 2 tone blue, 230k miles
82 Maxima Sedan, LD28, 3 speed auto, 2 tone Gray/Silver, 140k miles
81 810 Sedan, LD28, 3 speed auto, rust, rust, and more rust!

2005 Jeep Liberty CRD

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