I Blew my Headgasket in a 85 Z24 720 4x4 KC need help

[trjerm]

Hi I blew my headgasket in my 85 720 KC 4x4 yesterday going uphill and it overheated and started to loose power so I pulled mover and it died.Once it cooled down and I added some water , I tried turning it over but it was struggling and pumping water out of the radiator neck.I called a tow truck and when I got it home I pulled the plugs and then turned it over and blew lots of coolant/water out of the plug holes. I then squirted some wd 40 down the plug holes. Today I got a Fel Pro Head Set (HS 9210 PT-1) and a thermostat and gasket and started to pull it apart. The coolant system (rad., thermo, hoses ) seem pretty rusty. Should I just replace the head gasket and thermostat or would you recommend getting the head pressure tested and machined. The eng & trans only have approx 30K on them and it was running great(passed smog w/ flying colors 1 yr ago(10K) and getting 17-18mpg) Also what are the dimensions for the wedge and exactly how do you install it?? ie do you pull the cam gear bolt before you tap the wedge in place and if so how do you hold the cam gear in place while you tap the wedge in place?? I made a 9" wedge out of a piece of 1 x 2 pine trim and it's dimension are  9" L x 1 5/8" W @ top , 1 1/8" W @ bottom x 11/16" W.  Thanks for any hints or insight, Tom

[datzenmike]

Loosen the cam retaining bolt but do NOT remove yet until the timing chain is wedged and secure so the tensioner will not pop out.

 

The wedge is 6 1/2" long and 1 3/4" tapering down to 1 1/4" and fits in below the cam sprocket. 9" is not going to fit. Drill a small hole in the top and knot a cord loop so you can pull it out when done. Set the engine to TDC and hammer it in securely. I place the shifter in neutral and apply the  e brake so jostling the car while working does not bump the engine and dislodge the wedge.

[trjerm]

Thanks I got the dimensions I used were from the Chilton 1970-88 Nissan Pickup /Pathfinder Manual (dimensions were for L 16 -20B engines and all it said was "Z series engine similar" and I couldn't see how to get it in w/ the cam gear bolt in place. Will I have any Issue w/ the Pine only being 11/16"T vs 3/4" T, if not I'll cut it down to 6 1/2" L and drill a hole and attach a small cord. Also do you have to pull the fan & radiator or just the power steering pump and do you roll it over w/ starter to get to TDC on #1 or w a socket and breaker bar on crank bolt. Also would you get the head pressure tested and machined or just slap a head gasket on??

[datzenmike]

Thanks I got the dimensions I used were from the Chilton 1970-88 Nissan Pickup /Pathfinder Manual (dimensions were for L 16 -20B engines and all it said was "Z series engine similar" and I couldn't see how to get it in w/ the cam gear bolt in place. Will I have any Issue w/ the Pine only being 11/16"T vs 3/4" T, if not I'll cut it down to 6 1/2" L and drill a hole and attach a small cord. Also do you have to pull the fan & radiator or just the power steering pump and do you roll it over w/ starter to get to TDC on #1 or w a socket and breaker bar on crank bolt. Also would you get the head pressure tested and machined or just slap a head gasket on??

 

Width is fine.

If just the gasket change, the rad and fan/pump stay where they are.

You can use the starter to get it close. Watch the front two cam lobes. When the front one is at 2 o'clock and the second one at 10 o'clock look on the crank pulley for the timing mark. Turn with a wrench and set to the zero on the timing scale. (this is after loosening the cam sprocket)

I wouldn't bother pressure testing it but I would check it for warpage. You are allowed 0.004" of warp across the length of the head.

 

Tightening sequence is...

 

RAD

7...8

3...4

1...2

5...6

9..10

 

Use this sequence and bring all bolts to 20 lbs, then

Use this sequence and bring all bolts to 40 lbs, then

Use this sequence and bring all bolts to 60 lbs

 

Head and block surfaces must be cleaner than clean! Spotless! Threaded holes cleaned thoroughly right to the bottom. Bolts can be reused multiple times as long as clean and undamaged. Do NOT use gasket sealers or dressings.

[trjerm]

Thanks for the advice 

[Guest Rick-rat]

Sorry, I have to ask, did your head gasket smoke a cigarette when you were finished?  :rofl:

[Twinpilot001]

Clean head & block surfaces-Clean- like mom does the dished-spotless!!  Now- some will agree  with me & some not-here goes- from building engines -many years - I always use a product called - K&W -coppercoat-SPRAY ONE!! used for sealing head gasket surfaces!!  I dont care if the gasket is coated or not!! spray the block, head & the actual head gasket!! then install -- torque all bolts in proper sequence &   enjoy!! You can also use a block/radiator sealer -i like "Bars leak"  even without the sealer in radiator- Ill bet you will never blow another gead gasket!! Coppercoat works!! Ive never =ever had any head gasket blow after i used the coppercoat stuff!! thats been now over 50 years!! Just used it on my napz 82 engine & my chev 383 build!! Happy Datsunnin!!

[trjerm]

well , I ended up taking the head to a machine shop, were I had them do a valve job, valve seals, machine the head flat, clean it in a tank, etc. I cleaned the block w/ a soft wire wheel, Then Installed a new fel pro head gasket set(HS 9210 PT-1). I also changed the upper and lower rad. hoses, thermostat and gasket and found that 1 of my heater hoses was leaking, therefore I changed it also. Then I adjusted the valves (cold .008 intake; .009 exhaust) and torqued the head in 3 steps to 60 lbs. When I started it up it runs great but is putting out white smoke out the exhaust (runs clean @ idle but when I accelerate to 3K or more it puts out white smoke. Any Ideas on what to do next, thanks Tom Also in the gasket set there was a approx 1/2 " copper ring that I didn't know where it went therefore I didn't install It.

[datzenmike]

Drive it a few miles to burn off any coolant or oil contamination. Keep an eye on the temp gauge and the rad level.,

[trjerm]

Ok , I'll try that' I did let it run for about 1/2 hr while I was flushing and refilling the coolant.

[datzenmike]

Can you tell if steam or thick oil smoke. If you are running antifreeze coolant (as you should) it will smell sweet. Oil smell like burning oil and when thick enough is white, when thinner and see through it's blue-er.

 

Often oil or coolant gets down the exhaust pipe when the gasket blows and takes a while to 'burn off'. Don't start worrying yet.

[trjerm]

seems to be steam and gets worse when I bring the revs above 3K

[wayno]

I would pull the easiest set of plugs(one from each cyl), and find out which cylinder is wet.

[datzenmike]

If it is coolant getting in it's likely the intake gasket. There are coolant openings below each runner on the intake that match up to the head.

 

These are Z24 and Z22 but upside down.

[trjerm]

Yep  I'll  have to pull the intake and see if I somehow messed up the gasket, I pull the exhaust side plugs(1 @ a time) and didn't notice and moisture coming out and it only seems to make white smoke @ high rpm (higher vaccum) hopefully I can just get the intake manifold gasket @ the parts store. what a pain but besides the smoke it seems to run great, I guess it'll be a good time to change the bypass hose also. Any hot tip on how to start the lower intake manifold bolts w/ the head in place??

[trjerm]

I replaced the intake manifold gasket that I F**ded up, and it runs great now. I still have something  wrong in the vacuum lines because the choke / high idle isn't working right when I first start it up. How I messed up the intake manifold gasket is I used copper coat and set the gasket to the intake manifold before I tried to install it, only to find out that you need to start the lower bolts before you install the manifold. So I tried using my exacto knife and cut the gasket so it would slip over the lower bolts and low and behold it sucked coolant into the intake @ 3500 and greater RPM.  Live and learn. Also my EGR valve sputters till it gets warm so wondering if anyone has a spare egr valve and pipe for a z24 that they'd be willing to sell. Also found a hole in the heater line from the block and thats what caused my coolant loss and subsequint overheating that took out my head gasket. Glad I had the valve job done in that the valves had slight pitting and now are perfect.

[84720FourWheel]

Tap the gas before start up to make sure the choke closes before you try to start. 

[datzenmike]

Gaskets go on dry.

 

The EGR is not working until the engine warms up, Also not at idle and full throttle. This is what the thermal vacuum valve does. It's an air leak that destroys the vacuum signal to the EGR. When the engine is warmed up the valve closes and the vacuum can now work the EGR. If you took the hoses off, then take the one to the EGR off and this will disable it.

 

 

 

On a dead cold engine... take the top off the air filter and look. The choke plate should be open or part open. work the throttle cable. You should see the choke snap closed fully. With the choke on the fast idle should be engaged also. Let me know what you find.

[trjerm]

Finally got around to checking the choke plate on a cold engine today, and yes it snaps closed when you play w/ the throttle cable. I don't think the fast idle is working as designed.

[datzenmike]

When the choke closes it releases the linkage that holds the fast idle cam up out of the way. The cam falls of it's on weight and the throttle closes on it and is held open, revving the engine. Spray W-40 on the linkage and work it up and down with the throttle held slightly open.

[trjerm]

thanks ,I'll try that tomorrow.

[720inOlyWa]

Manifold gaskets go on dry?.... (Gulp). I just saw stuff on there when I cleaned it and assumed that...

 

I am about to do the head gasket dance again with this 4x4 720 that I picked up and this thread is really a nice touchstone for that. Really helpful thread.  Mike- or anyone- do you replace the cam automatically when you have the head rebuilt? The machine shop guy I talked to said that often, they just automatically replace Toyota cams when they rebuild heads. Wasn’t sure about NAPZ cams. Do I ask them to check it, or will they do so as a part of the routine rebuild? Do the cams wear out, like timing chains and tensioners? Are they generally effected by blowing a head gasket??  Thanks.

[datzenmike]

If you have good clean level surfaces no gasket dressing is ever required. Won't hurt anything... just not needed at all. The other thing is taking the head off later. Used a 2x4 to pry a chevy head off once that had been shellacked on with dressing. Dressings are so 50s technology. Gaskets today are made with high tech materials and composites. Often the sealer is printed on and they don't require re-torquing.

[bryant2482]

cams can wear out over time. if the lobes are worn and cannot open the valves to their proper clearance then "YES" replace it

[wayno]

My machinist always checks the cam when I bring an L head in for work, it's an automatic thing at that shop.

 

I have always wondered about cams wearing out, and the fact is I have only seen one wore out one in my life, and that was in a 327 block, which were notorious for doing just that, the front of the cam hardly had any lobes at all.

The oil was also filthy in that block, and the scum was an inch thick everywhere in that block, under the intake manifold was solid muck, I would have assumed that the engine would have had a PCV valve being it was a 67, but it didn't have one that I know of, but that was 40 something years ago when that engine was tore down.

 

All that said, the oils they are selling today are not being made for are older engines, especially for breaking in new cams, in the future when I break in a new engine, I will use Delo400 diesel oil, it has more of what new cams need for breaking them in, and it likely won't hurt the engine either.