Jump to content


Photo
- - - - -

Replacing a head gasket on a 1986 Nissan King Cab Pickup with 2.4L NAPS-Z carburetor


  • Please log in to reply
19 replies to this topic

#1 sterlingstone

sterlingstone

    Hall Monitor

  • New Members
  • Pip
  • 5 posts
  • Location:Casper, WY
  • Cars:Nissan 1986 720 King Cab, 2004 Jeep Wrangler, 2002 Ford Explorer Sport Trac

Posted 03 August 2009 - 01:46 PM

I think that I have a blown head gasket between cylinders 3 and 4.
Does anyone have a quick and dirty list on changing the head gasket, pitfalls,
tips, etc? I think I can tackle it, but don't want to cause myself extra misery
with a dropped chain, ruined engine, etc etc etc.

Thanks in advance for your help.

SterlingStone@gmail.com

:D:)

#2 izzo

izzo

    Datsun Mechanic

  • Senior Member
  • PipPipPipPipPipPipPipPipPipPip
  • 11,350 posts
  • Location:Seaside Or
  • Cars:80 720 79 210

Posted 03 August 2009 - 02:10 PM

its super easy really

set your timing TDC, top dead center. And make yourself a datsun "Wedge" Then just read the book, should take you just an afternoon with a few tools, some beer and music...


The datsun wedge will go down in the timing cover and keep your chain from falling in, and the tensioner tight so the spring doesnt come out. if the spring comes out of that tensioner then your fucked and have to pull the timing cover and you will need more gaskets then. Its about 3/4" thick, 10 inches long, 1 1/2 inches wide on one end, and the other end should be about 1 inch wide.

Spray the intake/exhaust bolts good with some wd-40 or something a few hours before you do it so they come out a little easier. breaking a bolt on those sucks... especially if you have to dril them out and re-tap them

Edited by h2theizzo, 03 August 2009 - 02:15 PM.

http://threeinchesof...sport.ytmnd.com
Go eat a bowl of dicks
RIP Wide14u

#3 sterlingstone

sterlingstone

    Hall Monitor

  • New Members
  • Pip
  • 5 posts
  • Location:Casper, WY
  • Cars:Nissan 1986 720 King Cab, 2004 Jeep Wrangler, 2002 Ford Explorer Sport Trac

Posted 04 August 2009 - 12:53 PM

its super easy really

set your timing TDC, top dead center. And make yourself a datsun "Wedge" Then just read the book, should take you just an afternoon with a few tools, some beer and music...


The datsun wedge will go down in the timing cover and keep your chain from falling in, and the tensioner tight so the spring doesnt come out. if the spring comes out of that tensioner then your fucked and have to pull the timing cover and you will need more gaskets then. Its about 3/4" thick, 10 inches long, 1 1/2 inches wide on one end, and the other end should be about 1 inch wide.

Spray the intake/exhaust bolts good with some wd-40 or something a few hours before you do it so they come out a little easier. breaking a bolt on those sucks... especially if you have to dril them out and re-tap them


HOW DO YOU SET / KNOW THAT the TIMING IS SET TDC (TOP DEAD CENTER)?

#4 Buzzbomb

Buzzbomb

    Senior Member

  • Members
  • PipPipPip
  • 248 posts
  • Location:Rocky Mountains...
  • Cars:'80 720, '70 Chevrolet

Posted 04 August 2009 - 08:33 PM

TDC = timing mark lining up with 0 on timing tab

There is no quick and dirty way to do this...You have to be careful and detailed with this job, or you will probably be doing it again. Better get a Haynes manual if you don't have one and do a thorough search here at Ratsun. Also you can get a Z engine specific timing chain tool at Checker for like $5. I used the L engine version of this tool, and feel it was money well spent and then some. I know a lot of people use the wooden wedge, but if you have to buy a decent piece of wood if you don't have any laying around, you're nearly at the price of the tool.

Edited by Buzzbomb, 04 August 2009 - 08:35 PM.


#5 izzo

izzo

    Datsun Mechanic

  • Senior Member
  • PipPipPipPipPipPipPipPipPipPip
  • 11,350 posts
  • Location:Seaside Or
  • Cars:80 720 79 210

Posted 04 August 2009 - 08:53 PM

best investment i have ever made


http://discountautor...Category_Code=D



Some of the things i read in the book i am unclear about, but just read the book, try then ask here if you fail or dont get it. Never done a Z24 head gasket, but id think it would be really similar to the L series which was pretty easy.

Buzzbomb, could you get a picture of that tool i am curious about it.
http://threeinchesof...sport.ytmnd.com
Go eat a bowl of dicks
RIP Wide14u

#6 Buzzbomb

Buzzbomb

    Senior Member

  • Members
  • PipPipPip
  • 248 posts
  • Location:Rocky Mountains...
  • Cars:'80 720, '70 Chevrolet

Posted 05 August 2009 - 06:45 AM

H2theIzzo,

Here is the tool for our truck and earlier:

http://shop.oreillya...rtNumber=648831

I can vouch for this tool, as I said. It works GREAT, and there are no worries about whether the board was cut right, will it slip out, etc. It was a great investment. I THINK this tool was patterned after a Snap On tool from back in the day.

..And here is the tool for the other '80s NIssan engines that are not L20B, which means the original poster's Z24.

http://shop.oreillya...rtNumber=648832

Better get these now if you want one..I was told they are on clearance when I bought mine. ONce they are gone, that's it.

Edited by Buzzbomb, 05 August 2009 - 06:49 AM.


#7 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 47,502 posts
  • Location:Vancouver Island
  • Cars:'78 620, '74 710 sedan, '76 710 goon

Posted 05 August 2009 - 06:55 AM

TDC = timing mark lining up with 0 on timing tab

There is no quick and dirty way to do this...You have to be careful and detailed with this job, or you will probably be doing it again. Better get a Haynes manual if you don't have one and do a thorough search here at Ratsun. Also you can get a Z engine specific timing chain tool at Checker for like $5. I used the L engine version of this tool, and feel it was money well spent and then some. I know a lot of people use the wooden wedge, but if you have to buy a decent piece of wood if you don't have any laying around, you're nearly at the price of the tool.


Just be carefull. There are 2 TDC on a 4 stroke motor. Get the right one by removing the valve cover, it has to come off anyway, and look at the #1 cam lobes. TDC on the compressuin stroke of the #1 cylinder will see both cam lobes pointing upwards with the intake at 10 o'clock and the exhaust at 2 o'clock as viewed from the front.

Rotate the motor up to the TDC timing mark in a clockwise direction. If yo overshoot the mark, back the motor up well before TDC and try again. You must get TDC while moving in a clockwise direction to keep the chain slack on the tensioner side. Do this as many times as it takes to get it right.

Edited by datzenmike, 05 August 2009 - 06:57 AM.

youregdright.jpg


#8 Buzzbomb

Buzzbomb

    Senior Member

  • Members
  • PipPipPip
  • 248 posts
  • Location:Rocky Mountains...
  • Cars:'80 720, '70 Chevrolet

Posted 05 August 2009 - 07:00 AM

Just be carefull. There are 2 TDC on a 4 stroke motor. Get the right one by removing the valve cover, it has to come off anyway, and look at the #1 cam lobes. TDC on the compressuin stroke of the #1 cylinder will see both cam lobes pointing upwards with the intake at 10 o'clock and the exhaust at 2 o'clock as viewed from the front.

Rotate the motor up to the TDC timing mark in a clockwise direction. If yo overshoot the mark, back the motor up well before TDC and try again. You must get TDC while moving in a clockwise direction to keep the chain slack on the tensioner side. Do this as many times as it takes to get it right.



See, that's why you're KING RAT! :cool: ...It comes down to the details :D

Just out of curiousity, can you still verify TDC at #1 on a Z24 engine by looking at the where the rotor is pointing in the distributor since it has 8 plugs?

#9 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 47,502 posts
  • Location:Vancouver Island
  • Cars:'78 620, '74 710 sedan, '76 710 goon

Posted 05 August 2009 - 02:32 PM

You can but the rotor looks very different from the L series. It has two contacts and at TDC should point to the rad or 9 o'clock and to about 4 o'clock.

youregdright.jpg


#10 izzo

izzo

    Datsun Mechanic

  • Senior Member
  • PipPipPipPipPipPipPipPipPipPip
  • 11,350 posts
  • Location:Seaside Or
  • Cars:80 720 79 210

Posted 05 August 2009 - 06:51 PM

hey mike

just to verify


The z24 cam will point just like the l20 cam when at tdc?

Also, say i crank it to tdc clockwise and i miss it by a mm or two. itll be ok right i wont have to keep dinking with it until its exactly at 0. If i remember right the crank pulley will only slide on in 3 ways. position #1 #2 #3.

correct or am i off?
http://threeinchesof...sport.ytmnd.com
Go eat a bowl of dicks
RIP Wide14u

#11 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 47,502 posts
  • Location:Vancouver Island
  • Cars:'78 620, '74 710 sedan, '76 710 goon

Posted 06 August 2009 - 11:46 AM

hey mike

just to verify


The z24 cam will point just like the l20 cam when at tdc?

Also, say i crank it to tdc clockwise and i miss it by a mm or two. itll be ok right i wont have to keep dinking with it until its exactly at 0. If i remember right the crank pulley will only slide on in 3 ways. position #1 #2 #3.

correct or am i off?


At TDC compression stroke on L series, the cam lobes will be facing upwards with the intake at (about) 10 o'cllock and the exhaust at 2 o'clock.
Z series have rockers on top so the lobes must be down at 8 and 4 o'clock.

I would get it as close to the timing mark as possible. Just back the motor up well before TDC, and keep trying till you get it. This will assure that all chain slack is kept on the slack side and will also give the most accurate reading when you check for chain stretch. The crank pulley only goes on one way :D I know you meant the cam sprocket. Always mark the cam sprocket and chain so you can at least get it back to where you started. If there is chain stretch you will need this mark on the chain to set the new sprocket hole number on. L20Bs come set on the #2 from factory for emissions reasons, so you can only move it to #3 to remove any slack.

youregdright.jpg


#12 izzo

izzo

    Datsun Mechanic

  • Senior Member
  • PipPipPipPipPipPipPipPipPipPip
  • 11,350 posts
  • Location:Seaside Or
  • Cars:80 720 79 210

Posted 06 August 2009 - 12:01 PM

At TDC compression stroke on L series, the cam lobes will be facing upwards with the intake at (about) 10 o'cllock and the exhaust at 2 o'clock.
Z series have rockers on top so the lobes must be down at 8 and 4 o'clock.

I would get it as close to the timing mark as possible. Just back the motor up well before TDC, and keep trying till you get it. This will assure that all chain slack is kept on the slack side and will also give the most accurate reading when you check for chain stretch. The crank pulley only goes on one way :D I know you meant the cam sprocket. Always mark the cam sprocket and chain so you can at least get it back to where you started. If there is chain stretch you will need this mark on the chain to set the new sprocket hole number on. L20Bs come set on the #2 from factory for emissions reasons, so you can only move it to #3 to remove any slack.




lol... thanks mike

Good to know, i am about to pickup a new head gasket for my z24 and would have been fucked sitting out there trying to set the cam to 10 and 2 instead of 8 and 4... :lol: Thats 8 intake side and 4 exhaust side right?
http://threeinchesof...sport.ytmnd.com
Go eat a bowl of dicks
RIP Wide14u

#13 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 47,502 posts
  • Location:Vancouver Island
  • Cars:'78 620, '74 710 sedan, '76 710 goon

Posted 06 August 2009 - 03:50 PM

Intake @ 8 and exhaust @ 4. Or there abouts, this will place the timing mark close enough to find it near the timing scale bolted to the timing cover.

youregdright.jpg


#14 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 47,502 posts
  • Location:Vancouver Island
  • Cars:'78 620, '74 710 sedan, '76 710 goon

Posted 06 August 2009 - 05:26 PM

I think that I have a blown head gasket between cylinders 3 and 4.
Does anyone have a quick and dirty list on changing the head gasket, pitfalls,
tips, etc? I think I can tackle it, but don't want to cause myself extra misery
with a dropped chain, ruined engine, etc etc etc.

Thanks in advance for your help.

SterlingStone@gmail.com

:D:)


OK this took me a while to wright out but covers most stuff. I doubt it is totally complete so if there are any glaring errors let me know and I will correct the text as I can.




Head Gasket Change On L or Z Series Motors.

Since the head need only be removed to change the gasket there is no need to dismantle more than you need to. Keep it simple and cause yourself less work, expense and problems by removing it with both manifolds bolted to it. In the case of the Z engine the exhaust is connected to the intake by the brittle or rusty EGR tube that is a morning's work to remove often ending up needing to be replaced. There are intake/exhaust gaskets to replace and the risk of breaking or loosing something. You could remove the carb to prevent sediment stirring up and possibly blocking a jet. This also allows more leeway when removing and installing the head. If the head is to be re-built, planed or ported then it's still easier to remove the manifolds once it's off.




Removal:

Disconnect the battery and block the wheels so it won't move.
Place in neutral so bumping against the car won't jog the motor from it's TDC setting with the timing chain off.
Drain coolant at least half way.
Detach the upper rad hose at the thermostat housing.
Mark all wires and hoses so they go back in the same position!
Disconnect the temp sender wire.
Detach the heater hose from the right rear of the L head and from the fire wall on Z series
Unbolt the ground strap from the battery on the head behind the fuel pump on the L, and from the intake on the Z.
Disconnect the fuel and return lines at the pump then remove the pump on the L and the hard lines bolted under the intake on the Z. Do not loose the phenolic spacer under the L fuel pump. Tie hoses out of way to prevent dripping.
Remove the PCV valve hose from the intake on the L series and from the base of the carb on the valve cover side on the Z engine.
Remove the vacuum hose to the charcoal canister from the distributor and the other one from the vacuum supply on the intake on the L. There are three hoses below the front of the Z intake that connect to hard lines that cross over to the driver's side. Disconnect here. There are also several vacuum lines that go to the pass side fender, remove and label.
Unbolt the down pipe from the exhaust manifold.
Unplug the 2 or 6 wire plug at the back of the Z carb. On the L carb, disconnect the idle cut (Blue) and choke heater (Red) wires.
Disconnect the throttle cable.
Remove the vacuum hose for the power brake booster and tie out of way.
Disconnect the warm water return line from the intake manifold down at the lower rad inlet on the L series.
Remove valve cover and loosen, but do not remove, the cam sprocket retaining bolt after slipping a ratchet extension through the sprocket holes to lock the sprocket from turning.
Mark the sprocket and the chain so that the two can be re-alligned on assembly.
Turn motor so that both cam lobes on the number one cylinder are upward at aprox. 10 and 2 o'clock on the L series and down at 8 and 4 o'clock on the Z series motors.
Find the timing mark on the rear most pulley and rotate the motor up to the O (zero) timing mark. You may have to back the motor slightly to find it then turn clockwise up to the O. If you overshoot the O timing mark, back the motor up well before TDC and try again. You must set the O on the mark while turning in a clockwise direction, if you miss keep repeating until you do. This is critical for checking chain stretch later.
Once at TDC insert the timing chain wedge in place and hammer in tight. A wedge can be made from a piece of fir about 1/2" thick and tapering from 1 3/4" down to 1 1/4" over a 6 1/2" length. Or buy one.
From this point on the motor must NOT be rotated!
Remove the cam sprocket bolt and save the fuel pump ecentric on the L series.
Pop the cam sprocket off and allow the chain to settle down between the guides on top of the wedge.
Start unbolting the 10 head bolts starting on the outside (front and back) and working in to the middle. The L series uses a 10mm hex wrench while the Z uses a conventional bolt head. Collect the head bolts and their washers.
Don't forget the two 10mm bolts on each side at the front of the L head that clamp it to the timing cover. There are 4 of these on the Z heads.
Using the manifolds for leverage rock the head loose from it's guides and lift off. Maybe get help and remove hood for room.
Some coolant may leak out and into cylinders. Just soak up with cloths. Stuff the middle two cylinders with rags to keep dirt out.
Find and save the two round dowels that allign the head to the block. Clean and save for assembly.




Preparation is everything:

Remove an inspect the gasket for any other sign of problems. The pistons closest to the blow out may be exceptionally clean looking as will the valves in the head. This is due to coolant steaming the carbon deposits off and is normal. I like to use an angle grinder with a 'soft' wire wheel to remove old gasket material from the head and block. Go easy on the soft aluminum head but get it clean and shiny. Prevent dirt particles from entering the ports through open valves. Use rags in the middle two cylinders and clean them out thoroughly when they are removed after cleaning the block surface. Get the head and block surface as clean and shiny smooth as you can... this can't be stressed enough. You can't get it too clean. Clean the block threaded holes out with a bottoming tap if available. I have an old head bolt that I have ground the threads off in two placed down it's length. I wipe grease in these areas and screw into the block, reverse then forward, reverse forward and going deeper untill at the bottom. Any debris collects on the grease in the grooves and when removed can be wiped off. When finished the regular head bolt should easily screw in by hand. Clean threads will give the best torque reading and maximum clamping force. Clean the old bolts with a wire wheel and lightly oil. There is nothing wrong with reusing the head bolts. While working on the block inspect for cracks between bolt and water passage holes. It's up to you what you consider 'cracked and useless' but I think most motors will have some form of crack(s) if you look hard enough and it runs fine. I might care more if this was a racing motor but for a stock street one... (shrug)

Inspect the head at the blow out site. This is critical as driving with it blown could have eroded the soft aluminum. You should determine if the blown gasket was caused by a head that is warped or warped because of overheating from the blown gasket. Sometimes they just blow for no other reason but ... age? Sometimes the cooling system isn't involved and there is no overheating but check the head with a straight edge anyway. Warpage should be less than 0.004" or 1mm along the total length of the head. Check carefully in the area between cylinders. Severe overheating can cause a pucker in this area and the only cure is to have it milled. Inspect the valves. Usually the exhaust are light tan because they run hotter and the intakes are darker. Look for obvious chipping or cracking damage and any discoloration in one area around the valve edge as this may indicate valve burning. Fix or replace. This would be a good time to replace the seals but will add to the replacement time. Seals can easily be replaced later.

Edited by datzenmike, 06 August 2009 - 05:29 PM.

youregdright.jpg


#15 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 47,502 posts
  • Location:Vancouver Island
  • Cars:'78 620, '74 710 sedan, '76 710 goon

Posted 06 August 2009 - 05:27 PM

Instalation:

OK block surface is (relatively) crack free, clean and polished smooth with bolt holes clean. Head is in good shape or repaired, surface is clean, polished and level and we are ready to assemble. NOTE: make sure that the #1 cylinder cam lobes are still in the 10 and 2 o'clock position for the L series and 8 and 4 for the Z series to prevent an extended valve from being bent against a raised piston when torquing the head bolts down. The gasket you use is less important than how flat and clean the head is and how clean the bolt and hole threads and block surface is. The $70 Nissan dealler gasket will blow out in a week just as fast as the $23 NAPA one if the head is warped or the mating surfaces are dirty. Do NOT use any gasket dressing or coating, they go on dry and clean... this isn't the 1950s. Install engine to head aligning dowels and slip gasket onto the block. Lift head onto the block and assure that it seats down over the dowels. Install head bolts and washers into their respective sides.


Tighten the head bolts with a good torque wrench in this order to 1/3 of the final torque setting:

L series
RAD
7-8
3-4
1-2
5-6
9-10

Z series
RAD
8-7
4-3
2-1
6-5
10-9

Go back to the start and using the same torque sequence tighten to 2/3 of the final torque setting.
Go back to the start and using the same torque sequence tighten to the final torque setting.

Assembly is more or less the reverse of dissasembly. Place the cam sprocket up under the timing chain loop and allign the chain and sprocket marks. Lift the sprocket up onto the cam making sure the cam dowel fits into the back of the sprocket. If the cam was moved and this does not line up grip, the center of the cam away from any lobes with vice grips and turn it till the sprocket fits on. Do not try to turn or move the timing chain. Install sprocket retaining bolt loosely by hand. Don't forget the fuel pump excentric. Now you can remove the timing chain wedge, lock the sprocket and tighten the retaining bolt.

After several warm ups and cool downs, check the torque on the head bolts when the engine is cold. That's about it. The NAPS Z engines are known for blowing the head gasket at about 100K miles. Nissan is aware of this and recommends that at every tune up, each head bolt should be loosened one at a time and re-tightened to final torque setting. No one I know bothers with this and I don't know if the dealler service dept. bothers but it sure can't hurt either.

Edited by datzenmike, 07 August 2009 - 04:18 PM.

youregdright.jpg


#16 nismo dr

nismo dr

    Cool Story Bro.

  • Senior Member
  • PipPipPipPipPip
  • 9,381 posts
  • Location:Tigard, OR
  • Cars:1982 TE72 Corolla, 1993 Infiniti j30t

Posted 06 August 2009 - 05:52 PM

TDC = timing mark lining up with 0 on timing tab

There is no quick and dirty way to do this...You have to be careful and detailed with this job, or you will probably be doing it again. Better get a Haynes manual if you don't have one and do a thorough search here at Ratsun. Also you can get a Z engine specific timing chain tool at Checker for like $5. I used the L engine version of this tool, and feel it was money well spent and then some. I know a lot of people use the wooden wedge, but if you have to buy a decent piece of wood if you don't have any laying around, you're nearly at the price of the tool.


thats funny, the actual special service tool IS wood. Looks out of place in the special service/essential cabinet

"If in doubt, flat out" Colin McRae

 

http://www.ebay.com/usr/nismo_dr

 

 

 


 

 

 


#17 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 47,502 posts
  • Location:Vancouver Island
  • Cars:'78 620, '74 710 sedan, '76 710 goon

Posted 07 August 2009 - 04:24 PM

I used to have a wooden one that I made back in the mid '70s and kept it in the bottom of my tool box for over a dozen years. Anyone who saw it asked what it was doing there and why. I also had a 10mm spanner that I cut and welded so I could get at the top slack side guide bolt... still have it.

youregdright.jpg


#18 Pacific coast Datsun

Pacific coast Datsun

    Japanese trucking association

  • Senior Member
  • PipPipPipPipPip
  • 7,486 posts
  • Location:Arizona via San diego CA
  • Cars:76 Conqueror "Datsun powered" jet boat -73 PL 620 - 74 PL 620 - 94 D-21

Posted 03 January 2011 - 11:40 PM

Ill be doing this repair on my 85 720 w/ Z 24. TY for posting the info. & steps to do it right.

85 720--74 pl 620--94 D 21-- 64 L 320 [co-owner]--74 sundance 16 jet boat [L 20 powered]
Member- *Japanese trucking association*
*Southwest Datsun pickups*
http://www.southwestdatsunpickups.com/
HBbedgif.gif


#19 Bennn

Bennn

    Newbie

  • Members
  • Pip
  • 37 posts
  • Location:Colorado
  • Cars:1985 Nissan 720 4x4

Posted 03 January 2014 - 02:48 PM

Anyone have an extra z24 head mines trashed

#20 trjerm

trjerm

    Newbie

  • New Members
  • Pip
  • 23 posts
  • Location:pollock pines , ca
  • Cars:1985 nissan 720 4wd kc, 1998 subaru outback

Posted 28 September 2014 - 05:55 PM

I just blew a head gasket yesterday and it overheated and slowed down going up a hill. I had to get it towed home as it didn't want to start after cooling down and was struggling when I tried to turn it over. I got it home and pulled the plugs and it biew a lot of coolant / water out the plug holes. A couple of questions; should I get head machined and pressure tested or just replace the head gasket(it was running great): Also what are the dimensions  for the wedge I, I made 1 out of a 1 x 2" piece of pine trim that's 9" L x 1 5/8" W @ the top and tapers to 1 1/8" @ bottom x 5/8" T; Also how do you install the wedge, do you have to pull the cam bolt to hammer the wedge in place and  how do you hold the cam gear on while  you tap the wedge in place. The Engine/ Tans only has about  40K on it, but the radiator and thermostat look rusty and don't know why the head gasket blew. Any insight would be great , thanks Tom ( mI bought  a Fel Pro Head Set (HS 9210 PT-1) and a new thermostat and gasket thanks again Tom