Adjusting Valve Lash (Clearance)

[Jennys280Z]

Please see the attached drawing I magnified and colored for a reference in doing this job.

To do this job after pulling off the rocker cover, you will need:

15mm open ended wrench

17mm open ended wrench

Feeler gauge

The proper valve clearances are as follows:

Hot:

Intake .010" Exhaust .012"

Cold:

Intake .008" Exhaust .010"

First a brief rant about the manuals I've consulted about this: The Haynes manual gives no information about doing this task. In fact, it has no information about tuneups or troubleshooting at all, making it of little to no value, as usual. The FSM has two small paragraphs of inadequate info and the 1970-1979 Shop Manual has an acceptable amount of info for the do-it-yourselfer but it has led me to have more questions before I do this and I suspect this thread will be a great help to anyone else who's never done it before.

I need some help from y'all who have experience and have done this task before. Please don't think my questions are bad ones, though some may be. Please take it easy on me...someone with no experience can't have good questions every time!

1. When I pull the spark plugs out to turn the engine, the high voltage ignition is still all hooked up all the way to the spark plug wires. When I'm turning the engine by hand, is there any danger in the engine cranking? Should I disconnect something on the starter motor/coil/battery to prevent some kind of catastrophe I'm too inexperienced to know about? (I'm reminiscing of those World War II aircraft here, where ground crews often hand-started the engines with a mighty heave on the propeller blade. )

2. Should I use a breaker bar to turn the engine? I have one on order right now and this could be a good first use of my biggest tool.

3. What size is the crank pulley bolt? I felt the bolt reaching under the front of the car tonight to get an idea of the size of the bolt. It's huge...I would guess somewhere over 20mm in size. But I can't measure it with a combination wrench because it's recessed behind the crank pulleys and I don't own any sockets in metric size anywhere near that big to stick on there to check.

4. The drawing in the FSM and Shop Manual (see below) show a feeler gauge off to the right on the driver's side of the hood. Is it better/easier to measure valve clearance from the driver's side?

5. The Shop Manual tells me to torque the locknut down to between 36-43 ft. lbs of torque. How am I supposed to do that with an open ended 15mm combination wrench? I am also ordering a torque wrench of my own so I don't have to borrow one all the time, but it's a socket wrench like every other torque wrench I've seen. Do I just make sure the locknut is really tight, and call it good enough?

6. What is the best way to decipher which valves are intake and which are exhaust? Do the two valve types line up with the hole patterns on a cylinder head? Here is a photo of an N42 head on an L28 motor.

http://datsunpartsllc.com/cart/images/products/secondary/72.jpg

From front to rear, the holes are E-I-I-E I-E-E-I E-I-I-E. Maybe this is one way to correctly deduce what valves are what, but when you don't have your manifolds off to see the head, there must be an easier way to tell in a snap what kind of valve you're looking at just by looking at the rocker or cam?

7. If I'm doing a hot adjustment after the cold adjustment, do I have to screw the valve cover all the way on tight (or at all) when warming the engine up? I'm asking this with a general sense of concern that I have to work fast so that the temperature is relatively stable while I'm doing these clearance checks and adjustments. I'm obviously not going to be fast never having done this before. And the temperature difference between the 12th valve and the 1st is likely to be considerable.

8. Which way do I turn the 15mm rocker arm lock-nut to LOOSEN it? Clockwise or Counterclockwise?

9. Which way do I turn the 17mm adjusting nut to DECREASE clearance? Clockwise or Counterclockwise?

10. In the drawing below, which nut is which? Is the nut being turned by the left hand with the combination wrench the locknut or the adjusting nut? I'm guessing that "special tool" from Nissan is turning the 15mm locknut and this tool also has a torque readout on it?

11. I color coded in green, orange, and red what I'm trying to decipher from the drawing. It'd help reassure me if you guys could tell me what I'm looking at in those three colors. Thanks!!!

12. I don't have any sense of what it "feels" like to do this. About how sensitive is this adjusting bolt to the clearance of the rocker? Is a quarter of a turn of the wrench far too much or not nearly enough? Should I slide the feeler gauge blade ALL the way through between the rocker arm and cam lobe? It looks like in the drawing that the feeler gauge blade is poking all the way out the other side of the cam lobe but it's just a black and white line drawing and it's hard to tell what I'm looking at.

If you guys can answer all of these questions, I can definitely do this job myself. And if I can do it, nobody will have an excuse from this day onward. :)

Edited December 23, 2010 by Jennys280Z

[zKars]

Wow! Nice job of laying out all the issues. I'll start.

First, you need a 14 mm and a 17mm wrench.

The other issues are covered in archives several times. Search for "Valve Adjustment".

Oh, one warning. the hot and cold clearance specs have been reversed in some references. Hot are wider. Kinda counter intuitive, but true.

next!

[cozye]

http://www.picturetrail.com/sfx/album/view/1803105

1. Disconnect the coil high tension wire. Remove connector to fuel control relay to disable fuel pump so you aren't filling your cylinders full of fuel.

2. I use the cam nut to crank motor. i've also used the crank nut with fan removed. Fastest way to do it is just use a 1/2 drive wrench on the cam nut. Go clockwise only so you don't loosen the nut.

3. can't remember, 27mm maybe. Use 1/2 drive socket on cam and don't sweat the crank pulley.

4. Passenger

5. Tighten as hard as you can. If you want to use a torque wrench, just get some 3/8 drive crows feet. The lock nuts tighten hard and quick, so if you just muscle it, it should be good. Keep both wrenches on while tightening, because if you don't the adjustment nut will move a little and change your lash .001

6. Use link provide at top. Also, the valves line up with the intake ports and exhaust ports on the side of the head too. I just made an E-I-I-E quick reference like you mentioned and crossed them off as I checked them.

7. Just get he motor really hot before you start, and take the valve cover off quickly. Get everything organized first so you aren't wasting time figuring it out while the motor is cooling. If you can get it done in 30 minutes, you are fine. Don't worry about doing a cold adjustment first.

8. cant remember. It's easy to move once you loosen the lock nut. It will be obvious.

9. 17mm is the lock nut

10. lock nut is on bottom

11. orange adjust, green lock, red nothing.

12. Use the fit/no fit method. feeler gauges should feel like pulling a stick of gum out of the pack. No need to worry about feel though. If you are aiming for .012, then adjust it to where .012 fits, and .013 wont. If .012 will slide in like a stick of gum, but .013 wont' slide in without significant force. You are good.

The job is relatively easy. Once you do it 3 times you will fly through it without a second thought. There is no harm in being a little off the first time, then rechecking it 500 miles later to perfect your technique and for piece of mind. My first time I adjusted a little, then checked it again with motor much warmer later on and adjusted a little more. It's no big.

[olzed]

Jenny. Removing the spark plugs from a hot motor can result in the plug threads 'picking up', or what you may call 'galling'.It's when the alloy thread in the head, attaches to the thread of the spark plug. My son had this unfortunate occurance on an MX5 Mazda,

resulting in having to have two threads redone with 'helicoil'

Removing spark plugs or bolts on a hot motor can have dire results. I have had bolts break with very little effort applied, when working on a hot engine. These days I always let the engine cool before I do anything, also much more pleasant working on a cold engine.

My Haynes manual for L24 and L26 engines suggests

Hot----Inlet---.010----exhaust---.012

Cold---Inlet---.008----exhaust---.010

Sorry I don't have specs for a L28, but would guess it would be the same.

The lock nuts always seem stupidly tight, but a good wrench that fits properly and turn them the correct way and you should be OK.

If you know which way to turn the screws to take off the valve cover, then just apply the same thinking. Anticlockwise will loosen them.

Slip the feeler gauge between the heel of the cam and the rocker.

Just a thought on spark plugs.

When I put in new spark plugs I smear some copper coat on the threads, and this would save the threads from galling if they were removed from a hot engine.

Just my 2c.for what it may be worth.

Brian

[Jennys280Z]

Jenny. Removing the spark plugs from a hot motor can result in the plug threads 'picking up', or what you may call 'galling'.It's when the alloy thread in the head, attaches to the thread of the spark plug. My son had this unfortunate occurance on an MX5 Mazda,

resulting in having to have two threads redone with 'helicoil'

Removing spark plugs or bolts on a hot motor can have dire results. I have had bolts break with very little effort applied, when working on a hot engine. These days I always let the engine cool before I do anything, also much more pleasant working on a cold engine.

My Haynes manual for L24 and L26 engines suggests

Hot----Inlet---.010----exhaust---.012

Cold---Inlet---.008----exhaust---.010

Sorry I don't have specs for a L28, but would guess it would be the same.

The lock nuts always seem stupidly tight, but a good wrench that fits properly and turn them the correct way and you should be OK.

If you know which way to turn the screws to take off the valve cover, then just apply the same thinking. Anticlockwise will loosen them.

Slip the feeler gauge between the heel of the cam and the rocker.

Just a thought on spark plugs.

When I put in new spark plugs I smear some copper coat on the threads, and this would save the threads from galling if they were removed from a hot engine.

Just my 2c.for what it may be worth.

Brian

You're right Brian. The L28 has the same clearances as the L24/L26 and I should have listed them in the initial thread. I'll edit it to include them now. Good idea with the copper coat too. Thanks for the warning. I never heard of that before. xx

I'm tempted to do it cold at first for a lot of reasons (even if Eric will yell at me). One, I have butterflies. okay I can't help that. Two, when I don't KNOW what I'm doing, I'm slow. I've learned too many times that when I hurry with an old car I am going to break something hehe. Three, I want to do some extra little things like visually inspect the rockers/camshaft/chain really good, find piston-TDC for the first time ever, check the timing chain for stretch/alignment, make sure I don't have any stray in my crank pulley. And heck even getting the valve cover off and on is like a challenge for me. Even if adjusting them hot is far superior to cold, being able to do it carefully and at my leisure the first time outweighs the benefit otherwise. And like Eric said I can always redo it again after a few hundred miles anyway. Based on how I am with other stuff, by the 3rd time I do it, I'll be confident.

Edited December 23, 2010 by Jennys280Z

[Jennys280Z]

http://www.picturetrail.com/sfx/album/view/1803105

1. Disconnect the coil high tension wire. Remove connector to fuel control relay to disable fuel pump so you aren't filling your cylinders full of fuel.

2. I use the cam nut to crank motor. i've also used the crank nut with fan removed. Fastest way to do it is just use a 1/2 drive wrench on the cam nut. Go clockwise only so you don't loosen the nut.

3. can't remember, 27mm maybe. Use 1/2 drive socket on cam and don't sweat the crank pulley.

4. Passenger

5. Tighten as hard as you can. If you want to use a torque wrench, just get some 3/8 drive crows feet. The lock nuts tighten hard and quick, so if you just muscle it, it should be good. Keep both wrenches on while tightening, because if you don't the adjustment nut will move a little and change your lash .001

6. Use link provide at top. Also, the valves line up with the intake ports and exhaust ports on the side of the head too. I just made an E-I-I-E quick reference like you mentioned and crossed them off as I checked them.

7. Just get he motor really hot before you start, and take the valve cover off quickly. Get everything organized first so you aren't wasting time figuring it out while the motor is cooling. If you can get it done in 30 minutes, you are fine. Don't worry about doing a cold adjustment first.

8. cant remember. It's easy to move once you loosen the lock nut. It will be obvious.

9. 17mm is the lock nut

10. lock nut is on bottom

11. orange adjust, green lock, red nothing.

12. Use the fit/no fit method. feeler gauges should feel like pulling a stick of gum out of the pack. No need to worry about feel though. If you are aiming for .012, then adjust it to where .012 fits, and .013 wont. If .012 will slide in like a stick of gum, but .013 wont' slide in without significant force. You are good.

The job is relatively easy. Once you do it 3 times you will fly through it without a second thought. There is no harm in being a little off the first time, then rechecking it 500 miles later to perfect your technique and for piece of mind. My first time I adjusted a little, then checked it again with motor much warmer later on and adjusted a little more. It's no big.

OMG!

[Jennys280Z]

Wow! Nice job of laying out all the issues. I'll start.

First, you need a 14 mm and a 17mm wrench.

The other issues are covered in archives several times. Search for "Valve Adjustment".

Oh, one warning. the hot and cold clearance specs have been reversed in some references. Hot are wider. Kinda counter intuitive, but true.

next!

Thank you...I agree it's counter-intuitive.

I did search before posting but searched for "adjusting valves 280Z" and got four or five matches. On a lighter note maybe this post won't be more redundant than it is beneficial...?

[rxsleeper]

What/\ said but I suggest you invest in one of these:

http://www.handsontools.com/KD-Tools-2424-Go-No-Go-Feeler-Gauge_p_6113.html#

A go/no-go feeler gauge. Then you can set clearance spot on with no worries.

Good luck!

[cozye]

Thank you...I agree it's counter-intuitive.

I did search before posting but searched for "adjusting valves 280Z" and got four or five matches. On a lighter note maybe this post won't be more redundant than it is beneficial...?

you can check them cold if you want to get a feel for it, but I wouldn't adjust them cold. The cold adjustment spec is very rough and only meant for getting them close on a new build or valve train replacement scenario. If you adjust them cold and they are already close, you will just have to adjust it hot again.

[cozye]

and if your plugs have already been removed, i wouldn't worry about removing them hot. They won't be seized and will come out easily. I've done this dozens of times. Technically you don't even need to remove the plugs but it will make cranking the motor over easier. FWIW I don't remove them, but I'm a strong guy and can crank the motor over by hand with a ratchet.

[FastWoman]

Yeah, I'd just leave the plugs in. I'm medium-strong ("sturdy") and don't really have any trouble. As long as you turn the engine slowly, the gasses will move around for you. (I turn the engine with the cam nut too.) However, if you want to remove the plugs, just remove them with the engine cold, lube the threads with antisieze, and put the plugs back in just a bit loosely (i.e. with a light twist of the wrench). That's adequate for running the engine to warm it up, and it shouldn't be so tight as to gall your threads when the engine is hot.

Save the final torquing of your spark plugs for after your engine has cooled!

Starting cold and moving to hot sounds like a reasonable plan. It would give you the opportunity to loosen all the lock nuts beforehand, so the hot adjustment will go faster. When retightening the cold nuts, I'd do it somewhat loosely to start with. They'll hold their positions just fine for the short time you'll be running your engine.

When you're doing your hot adjustments, go ahead and tighten the lock nuts back up while the engine is still hot. Galling isn't as likely an issue when aluminum isn't involved.

Edited December 23, 2010 by FastWoman

[Zed Head]

One advantage to doing them cold first is that many, maybe even all of them, will be in spec. when you check them hot. If they are in spec. you don't need to loosen the locknut, just move on to the next one. You will end up only actually adjusting a few of them hot.