Adjusting Valve Lash (Clearance)

[Gary in NJ]

Should I disconnect something on the starter motor/coil/battery to prevent some kind of catastrophe

Disconnecting the battery is a good idea.

Should I use a breaker bar to turn the engine?

With the plugs removed, you wont need much more then a 1/2 drive socket, but the breaker bar will make it easier.

What size is the crank pulley bolt?

I'm at work, so I'm guessing here, but I think it's 35mm.

Is it better/easier to measure valve clearance from the driver's side?

Passenger side.

The Shop Manual tells me to torque the locknut down to between 36-43 ft. lbs of torque.

As mentioned above, go to Sears and get a set of metric Crows Feet. Use the lower value on the Torque Wrench because the longer arm of the crows foot wrench requires an off-set value.

What is the best way to decipher which valves are intake and which are exhaust?

Simple. Look at the valve and see whats across from it. If it's the exhaust manifold its and exhaust valve. If it's the intake manifold it's an intake valve.

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?

It's a "warm" adjustment. Removing the valve cover only takes a few minutes. Take your time, it doesn't have to be hot.

Which way do I turn the rocker arm lock-nut to LOOSEN it?

Lefty loosie, righty tightie.

Which way do I turn the 17mm adjusting nut to DECREASE clearance?

Lefty loosie, righty tightie.

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?

This is the step where a third hand is...well...handy. If you have a helper, have that person hold the adjuster steady as you simultaneously move the feeler (to feel if it's getting tight or loose) and tighten the lock. If you are on your own, watch the feeler as you hold the adjuster and tighten the lock. If it moves up, it just tightened on you and if it sags it went loose.

I don't have any sense of what it "feels" like to do this.

Know this - this is an easy job and when you develop the "feel" for it, it's actually fun. You'll probably do the first few valves over when you finish the job because by the 12th valve you'll have the drill down.

Edited December 23, 2010 by Gary in NJ

[olzed]

Jenny .Out fo all this, you should have enough knowledge to give her a decent valve setting.

Don't panic, as there isn't really anything you can do wrong, unless you drop something

into the motor, which would not be good!!!

Good luck.

I'm going to be spending the next few days skim bogging and re-spraying a front fender on my 240. I had the whole car baremetal resprayed 11 years ago and for the last couple of years have been chasing bubbling surface rust on both fenders. The 'experts' had put a skim of bog straight onto bare metal, with the results that rust forms where the bog is not adhered to the metal.

After taking off the paint to the metal then sanding of any rust marks, I have been putting zinc rich etch primer on first then standard primer, then skim bog,to take out some ripples, then more prime. Am I doing it right? Sorry to get off topic here!

Happy Christmas everyone .

Brian. From down under.

Edited December 23, 2010 by olzed

[FastWoman]

"Know this - this is an easy job and when you develop the "feel" for it, it's actually fun. You'll probably do the first few valves over when you finish the job because by the 12th valve you'll have the drill down."

I completely agree. It's a pretty part of the engine, the parts are not difficult to work on, and it's indeed sort of fun. When you're done with it, you'll smile broadly and think, "Gee, I did that!" (Guaranteed.) One of the big disappointments of the DOHC '92 Saturn I bought to replace my beloved '75 Z from many years ago was that the hydraulic lifters (correct term?) required no adjustment. One of the pleasures of my "new" '78 Z was that after all these years, I got to crack open the valve cover and adjust some valves again. Weird, eh?

Edited December 23, 2010 by FastWoman

[Jennys280Z]

Thank you all so much! Sarah, Eric, Brian, Gary, Bob and all our fellow readers and posters. Luv u guys! And Merry Christmas, everyone!

[olzed]

Jenny. Just think things through and you will be fine, and don't panic. It's not really rocket science.

If my fender respray is any good i'll post a picture.

Yes and happy holidays to you and all on this awsome forum.

Brian. 240Z:beer:

[black240]

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!

hey guys just think of it this way. when your taking in atmospheric air, its gona be a heck of alot colder than inside your hot block. in other words, its gona be really dense. liquid water is far more dense than frozen water (why ice floats on water), thats why when you leave a soda can/bottle in your freezer it blows up so to speak due to the expansion of the more compact liquid h2o turning into ice. the same applies for gasses, sooOOoooo to take this into account the thermal expansion going on in your cylinder head, you need to take out more hot air when compared to bringing in cool air, that way well have a steady state type of flow.

[Jennys280Z]

Next to the valves, I almost forgot that I also want to tighten my cylinder head bolts once I get the rocker cover off. I suppose I should do that cold before my first cold valve adjust/check.

[Gary in NJ]

Next to the valves, I almost forgot that I also want to tighten my cylinder head bolts once I get the rocker cover off. I suppose I should do that cold before my first cold valve adjust/check.

Hold on there, not so fast.

I believe the bolts are stretch fit bolts and are intended to be (final) tightened once. The tightening sequence is to tighten all bolts to 32.5 ft-lbs and set final torque to 47 ft-lbs. The bolts are tightened from the center (cylinder 3) to the outer (1 & 6).

If you have a loose bolt or bolts, then you may also be in need of a head gasket. Is your head gasket leaking?

[FastWoman]

Jenny, it's useless and potentially a Pandora's box to mess with the head bolts. They're likely corroded, so torque will be irrelevant. The best case is that you do nothing useful. The worst case is that you snap a head bolt.

[az240z]

That reminds, many years a go I bought a z from somone for $250. It had a blown head gasket. We got it home and went to pull the head and found that the center bolt had sheared itself in half. Well the head we were going to use had the same problem. It too had a rusted thru bolt in the center that had broken.

WE both thought what a coincidence that two engines would have the same problem. In fact the second engine never showed any showed any signs of having a problem.

We eventually replaced the whole engine.

[olzed]

Yes Jenny .Sarah and Garys posts. ------ If it aint broke, dont fix it.'

Brian.

Edited February 18, 2011 by olzed
Late night

[Jennys280Z]

Hold on there, not so fast.

I believe the bolts are stretch fit bolts and are intended to be (final) tightened once. The tightening sequence is to tighten all bolts to 32.5 ft-lbs and set final torque to 47 ft-lbs. The bolts are tightened from the center (cylinder 3) to the outer (1 & 6).

If you have a loose bolt or bolts, then you may also be in need of a head gasket. Is your head gasket leaking?

Nope just regular maintenance according to my shop manual. Step one in a major tuneup if you will.

But I'll follow the advice here. No problem, then no need to touch it. Thanks!