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jlawley97

z24i vs z24 heads

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I am having some trouble with my z24i oil and water are mixing there is some hissing when i run it and it wont idle with out me pumping the gas. now this is after I have changed the head gasket and gotten mine machined. I am assuming something is cracked and I am getting the head pressure tested monday. 

now if i need to buy a new head would z24 work with my z24i manifolds and block. I have read conflicting reports saying the manifolds will fit or not fit. I know the blocks are same so I am not worried if that is what needs to be replaced just that z24 head are cheaper and more plentiful than the two years that z24i were around in america

thanks guys 

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It's not common for aluminum Z heads to be cracked so I doubt it's this.

 

Possibly the intake is not sealing to the head. There are water passages under each runner to warm the intake air in cold weather. If not sealed, coolant can be sucked into one of the cylinders and it's bound to get past the rings and into the oil.

 

Is there any obvious wetness under the intake? 

Does the exhaust run very steamy when warmed up?

 

Hissing is likely a hose off. Find this and fix and it will probably run again.

 

 

 

All Z24 heads have squarish ports with rounded corners. The earlier Z20 and Z22 heads with round ports will work but.... just get a Z24i head, carburetor or EFI.

 

The model year changes in June of the previous year so June '85 is the beginning of the '86 model year. '86.5 would be around Christmas/New year '85/'86.

 

The Z24i was available from April '85 (right near the end of the '85 model year) and for 5 or 6 months into the '86 model year. It was also used on the '86.5 model year through June '89 on the D-21 Hardbody and from June '86 through June '89 on the WD-21 Pathfinder. So many more years that just the 6-7 months at the end of the 720 run. There was significant differences in the EFI on the later Z24i but the heads would be the same. I have an later D21 Z24i engine and head that was converted for use on an '84 carburetor 720, so.... heads are the same.

 

 

 

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I am having the head pressure tested tomorrow. So it is more likely that the block cracked?? because I see no other reason that the oil and water would be mixing besides a crack at this point 

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Take a good look at the intake gasket. Is it folded or torn and does it have a good imprint that it was torqued on properly? Are the mating surfaces, intake and head smooth?

 

Also take a good look at the head gasket. Does it also have a good imprint that it was torqued properly? Are the two alignment dowels in place on the block?

 

 

Why was the head gasket replaced anyway?

 

 

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yeah everything is smooth. intake gasket is good as well. I had a friend torque and re torque to specifications. that may be an issue like they may have done incorrectly.

I changed the head gasket because

i had some problems with the thermostat opening so it was getting hot some times some times up to the section right before the danger section. I would pull over if i got any higher  but i would drive it like this just slightly above center alot. (I did not think it was an issue at the time i just thought thats where it would sit i now know it was an issue)

 

at first i was burning some oil burning some oil I thought this may be valve stem seals but i just kind of ignored it because I was busy waiting til i  got on vacation to do something. then on the first day of vacation i go to drive it about a mile and something is super wrong I am down on power and i blowing alotta lotta white coolant smoke. so I just assume this to be a head gasket from it getting too hot sometimes.  there was no other symptoms leading up to this it was like some popped all of a sudden so i assumed again headgaskets do that(I own alot of subarus) 
so i take it off get it machined 
the machinist says its wasn't very warped like he only too off .008 inches.

I lap the valves and put it all together. I had the chain held with o

it wont run at all. turns out machanical timing was 180 off( nothing was hurt i cranked several times by hand with no issue)
i correct this and it wont stay running just like it is now. so i drain the oil and notice it is milky which makes me nervous.

so i take the front cover off line everything up perfectly, put in all new fluids and then here i am it wont idle, the oil is milky again and some hissing from around the throttle body

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Temp gauge is normally in the middle of the 'run range'. When ever there is an over heating problem change the thermostat. This may have caused the gasket to blow but...

It's common for the head gasket to blow on the Z24 at 100k intervals. The preventative measure is to re-torque the head bolts every tune up. But no one ever does.

Max warp is 0.004" so yeah needed doing.

Hissing... look for loose or missing hose. If the TBI was unbolted re-seal it. Or find the air leak. If the air filter was off it's normal to hear a loud hiss from the throttle plate. Try a length of garden hose to your ear and the other end moved around the TBI base.

If you lapped the valves I hope you bothered to replace the guide seals then when it was easy.

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On 12/30/2018 at 4:09 PM, jlawley97 said:

what about the oil and water mixing?

 

 

If coolant gets into the cylinder as water, or steam, it will get past the rings from the high pressures generated. If you drive long enough with a bad gasket it's only normal that water mixes with the oil.

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okay well all the gasket seal were fine and the head pressure tested fine so can i assume the block?

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Most blocks have cracks around the head bolts and the coolant openings into the head but it does no harm. There's no easy way for the coolant to get way over to the cylinder.

 

 

Take the water pump off and inspect the cavity it sits in. If running without antifreeze coolant mix the impeller can cavitate and erode a hole in the timing cover.. A worn out pump bearing can wobble the impeller and rub a hole in the timing chain cover. Water drips down behind it and right into the oil pan.

 

 

See the square hole? that's where the water from the pump enters the block from the timing cover in front of it.There's a gasket around it and also a groove so that if the gasket leaks the water will find it way out to the side above the alternator. That would be very rare but you could have a look where the timing cover meets the block just below the return rad hose.

JXjXFLb.jpg

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The Z24I parts motor I have, there is a Kangaroo embossed on the head.  A friend of mine from Guam said that the kangaroo head flows better and he was really interested in getting it.  I gave him the engine and he ended up giving the engine back to me, he had to move back to Guam because Caterpillar offered him a job with a starting bonus and paid to move him, his wife, one year old child, and 4 of his trucks.

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HmqWCGm.jpg

 

A roo? I have a transmission with NMCA cast into it. Looked it up and there is a Nissan Motor Car (or Company) Australia that does casting.

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2 hours ago, datzenmike said:

 

HmqWCGm.jpg

 

A roo? I have a transmission with NMCA cast into it. Looked it up and there is a Nissan Motor Car (or Company) Australia that does casting.

There is actually a thread here about that head..... 

You even showed the same transmission tailhousing photo...

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Thought it was deja vu

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So when i am cranking the thing by hand I can hear hissing from the head area. Like it might be the valves but maybe the block is warped? 

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I will get a picture of the kangaroo on the head.  It is small but I will do my best.

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Hissing is not uncommon when hand cranking an engine. Pressures of over 150PSI are common and it squeezes past the rings.

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