Jump to content

z22 Timing chain tensioner question


Recommended Posts

Hello distinguished, knowledgeable, Nissan enthusiast's,

 

It's been quite a while since I last visited and an issue requiring your expertise has once again surfaced, though I believe I know the answer - Please bear with me as I submit an rather lengthy explanation of the situation:

 

I've finally decided to R&R the cylinder head on my '82 720 (Z22 w/3 speed automatic - California smog) which has been sitting in storage for a couple of years. Prior to storage I'd accumulated about 6k miles since inheriting the truck and would notice a plume of white smoke emanating from the tailpipe, now - this wasn't a daily nor mileage dependent occurrence. It was totally random.  I never bothered pressure testing the cooling system to check for pressure bleed down or pulling plugs while cranking in search of coolant vapor/mist. I didn't have any evidence of chocolate milk-like emulsified oil when I pulled the valve cover for a valve adjustment, though another telltale symptom was intermittent hitting on 3 cylinders - but - this didn't coincide with the white smoke. It would randomly run on 3 cylinders for only a few seconds then revert back to running normally on all 4. New Cap and Rotor with new NGK plugs and wires so its highly unlikely for the ignition to be the culprit. Also, I never noticed the temp gauge show it as running hot. I also entertained the thought of a failed/failing transmission vacuum modulator as the odor didn't have any coolant sweetness to it, nor did it smell like motor oil. If anything, it smelled more like ATF than anything else.

 

Anyhow, I chalked it up to a failing head gasket, perhaps not a catastrophic failure but one on its way out be it due to electrolysis or perhaps an unbeknownst to me prior overheat incident. So, the truck was parked while I looked around for a replacement, remanufactured, cylinder head just in case mine came back from the shop as being cracked. I also found a new (not rebuilt) OEM carburetor and slowly acquired the necessary parts, gaskets, hoses, etc. for the R&R. I figured this would be a creative, instructive project to undertake with my 15 year old son so yesterday, we started getting everything stripped down ready to finally remove the head and finally - here is the question I believe I know the answer to.

 

I specifically instructed Bill (my son) to wedge a wooden V block I'd made, in place down in the timing cover cavity before pulling the cam gear with all marks lined up and crank at '0' - anyhow, while I was busy answering a phone call he didn't properly wedge the block in place and now, obviously, the tensioner is at its end of travel. Now, the timing cover, all associated components (oil pan, etc) are covered in 34 years worth of caked on grime.

 

Is there any way to get the tensioner to bleed down enough to reinstall the cam gear once we R&R the head or do we now have to pull everything apart, i.e. remove timing cover, tensioner, etc?  

 

As I mentioned, I believe I know the answer but perhaps there's a better way?

 

 Thank you in advance for your valued responses.

 

 Joe

Link to comment
  • Replies 19
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

tensionerout.jpg

 

This is what you will find. That spring is very stiff and the tensioner very hard to push in and hold in place. Best put in with the head sitting on the new gasket but not bolted down and the chain on the sprockets. Then bolt the timing cover on, then the oil pan and torque the head down. The loose head will allow you to slide the timing cover on under neath it.

.

  • Like 1
Link to comment

Alright gentlemen, we've removed the head to find, as suspected - a blown out head gasket (fire ring) at the #1 cylinder with the accompanying steam cleaned piston crown and combustion chamber. The bores still have a reasonable cross hatch and I can't feel any significant ridge using the fingernail test. The piston tops have a large '2' followed by a small consecutive '3' up near the front reference notch so I don't know if it's been overbored or not - I'm certain one of you will know. 

 

I do have another, more pressing question though. We compared the old and reman head side by side and found a couple of significant differences.

 

The head we removed looks almost identical to the reman except for - what appears to be some kind of unused, threaded sensor boss at the #1 cylinder exhaust side sparkplug access window, whereas the reman head has no such boss. Secondly and most importantly - The combustion chamber volume is significantly different between the two in that the reman head has virtually no ledge or step from the deck to the valve seat. The old head has a good .040+ (if not more)

 

Then we realized the casting numbers are different which obviously indicates a different, perhaps earlier/later z22 application?

 

Our old head has casting code T83 whereas the reman is a W04. Now, I'm no mechanical engineer but DO know if the W04 head was surfaced to the point of eliminating that ledge then a tensioner issue is imminent, unless of course a head gasket shim is available to offset the difference?

 

We're once again turning to your collective expertise for clarification and much valued advice.

 

a most appreciative thank you in advance. 

 

Joe

 

     

Link to comment

The W04 casting is a Mileage option Z20 head used on the '83-'86 720. It has about 10cc less combustion chamber volume than your Z22 head and produces a 9 to one on the Z20 engine. On a Z22 this will increase yours to 9.8. Not at all good.

 

I would return this head and make sure they send the correct one. This head was never used on any Z22 engine.

 

 

This is the W04 head. It has about 10 cc less volume and a left and right side quench areas. (that flat area on each side)

motorZ20Sfrom7201-1.jpg

Link to comment

uh-oh. Not good news. This head was purchased off of eBay and there are no returns. I looked around for quite some time and couldn't locate a z22 head until this one showed up. I suppose I'll have to have my old head checked for cracks, warpage, and then a valve job.

 

Thank you, as always - for this valuable info!

 

best,

Joe

Link to comment

I just sent the seller a message citing the information you've provided and yes indeed you're absolutely correct - the seller specifically listed the head as:

 

"Nissan Datsun Truck Z22 D21 720 rebuilt cylinder head 2.2 2.2L 80-93" 

 

Price was $174.95 with $35 for shipping.

 

It was obviously incorrectly listed, however I purchased it March 31st but haven't had a chance to do the R&R until now and the seller notes:

 

"30 days money back - buyer pays return shipping"

 

I'll see how they handle this, hopefully and particularly because it was incorrectly listed they'll resolve the issue without conflict.

 

best

Joe 

Link to comment

9.8 isn't extreme. Run it.

 

 

And Mike is doing his math without knowing what pistons you have in the engine. An assumption. Sorry, Mike.

 

 

Run colder plugs. Dial your timing down a bit. Run higher octane gas. Call it done.

  • Like 1
Link to comment

Only the S110 had the early and late Z22 pistons. All 720 Z22 were the same early pistons with 9.32cc dish. (same part number) My compression is based on this.

 

 

The Z20S 'Mileage Option' engine in the '83-'86 720 had 9 compression. It also has the same flattop pistons as the early Z20E in the S110 (same part number) By reverse engineering, the W04 head must have a combustion chamber that is almost exactly 10cc smaller than the usual Z20E/Z22/Z24 head which I have cc's myself at 57.

 

If you want, I wrote a 'How to cc Your Head for Free'  http://community.ratsun.net/topic/358-how-to-cc-your-cylinder-head-for-free/ so you can verify the Z20 head you have is about 46 (ish) cc's. One or two cc's will bump it slightly one way or the other, but 9.8 is a bit rich. Even the Mileage Option Z20 in the 720 used a knock sensor and ignition retard system to tame the pre ignition.

 

Not saying you can't run this head. It's totally up to you.

  • Like 1
Link to comment

Considering these are emission compliant powerplants fitted with both EGR as well as pulse air, combined with a system calibrated carburetor (I have a new OEM carb in the box I'd like to employ as well) - I tend to agree with Mike. I'm incapable of out-engineering Nissan and if they utilized a close loop system with ignition control on the higher compression variant then I believe any adjustments of the current components for satisfactory overall performance - regardless of fuel used would be an effort in futility.

 

However, I certainly do appreciate your input and did give it some thought flatcat19.

 

Thank you both.

 

best,

Joe

Link to comment

Alright gents.We removed the intake and exhaust valves on the old head and all of the faces and seats are in remarkably good shape with no evidence of pounding and/or receding - also the guides and valve stems were in equally good shape with negligible radial wobble when inserted as little as 15-20mm into the guides from below so I've dropped it off to be checked for cracks and resurfaced requesting the absolute minimum of material to be removed - just enough to clean up any warp which might exist . We've removed the timing cover, preparing the surfaces and are now awaiting the shops call after which we'll seat the valves (though probably unnecessary) here at home with valve grinding compound and a hand dowel with suction cups. 

 

I DO have a factory shop manual which I purchased on eBay and unfortunately I just discovered its well used with many of the related pages heavily greased and unreadable. Can someone please guide me to an appropriate site showing cam timing marks as well as Ignition distributor clocking and corresponding firing order plug wire orientation. I didn't bother taking notes as I figured (incorrectly) I'd be able to use the shop manual.

 

again, and with profound thanks -

 

Joe  

Link to comment

Alright gents.We removed the intake and exhaust valves on the old head and all of the faces and seats are in remarkably good shape with no evidence of pounding and/or receding - also the guides and valve stems were in equally good shape with negligible radial wobble when inserted as little as 15-20mm into the guides from below so I've dropped it off to be checked for cracks and resurfaced requesting the absolute minimum of material to be removed - just enough to clean up any warp which might exist . We've removed the timing cover, preparing the surfaces and are now awaiting the shops call after which we'll seat the valves (though probably unnecessary) here at home with valve grinding compound and a hand dowel with suction cups. 

 

I DO have a factory shop manual which I purchased on eBay and unfortunately I just discovered its well used with many of the related pages heavily greased and unreadable. Can someone please guide me to an appropriate site showing cam timing marks as well as Ignition distributor clocking and corresponding firing order plug wire orientation. I didn't bother taking notes as I figured (incorrectly) I'd be able to use the shop manual.

 

again, and with profound thanks -

 

Joe  

Very much the same as the L series stuff.  Get another book...

Link to comment

CAM TIMING

 

Set TDC.

 

The crank sprocket has a dot at roughly 4 o'clock as viewed from the front.

 

The cam dowel, should be in the #2 hole on the cam sprocket

 

The cam sprocket  will have a dot at roughly 2 o'clock. Set the cam sprocket in this position before placing on the block. (within an inch or two)  DO NOT try to rotate the cam with engine stopped at TDC. If you find you have forgotten to set the cam, remove the rocker arm shafts so that all the valves close... then turn into position. Failure to do this can bend a valve stem.

 

Now install the chain and make sure there are 40 links between the two dots. Some good chains have two bright links 40 links apart, which makes it easy.

 

 

 

IGNITION

 

Set TDC.

 

Install oil pump spindle so that you see this looking down into the distributor hole...

 

distributortiming.jpg

 

NOTE that there is a small and large half moon shape on either side of the tang.

 

All Z series dual plug heads are wired this way from the distributor, as seen looking in from the left fender.....

 

720timing002Large.jpg

 

 

.

  • Like 1
Link to comment

Mike,

Your expertise on these vehicles is invaluable and if you were local, you and your lady would be having dinner on me. Alright, we've started it up and discovered we have no power going to both, the choke thermostat and obviously the idle control valve since they're both on the same circuit and I don't have a wiring diagram to trace it - is there a relay or perhaps a thermo-time switch?

 

Joe

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.