d21 z24 carburated strange rattling noise

[ari falco]

Hi everybody !!
I take a chance to ask you in here as a last resort before I sell my junk car.
I am the owner of a 1987 Nissan 4x4 d21 z24 carbureted.
First of all, the engine has been completely rebuild, new pistons and everything related to that , new head and gasket , new valves , and new timingchain/kit. , etc etc.....
I swapped out the old carburetor with a much better , (rebuild one).
The problem from the beginning was that the engine could not stay idle, at least not at 8-900 rpm as it should. at 1000 rpm and above idles fine.
And from the begining i had this rattling noise from the engine , not at startup , but when i release the gaspedal after acceleration and kept the gaspedal in the midrange . no specific rpm.
When i accelerate and braking with engine no rattling noise , only with gaspedal in midrange, (sounds like a dieselengine).
The first time at the workshop they said its the timechain....Since then, the timingchain and tensioner has been changed three times,(within a year and a half), with no result.
BUT !!!!..
I tried myself to set the advance by rotate the distributor , at some point the idle went up but the rattling got worse , (not at idle but when i gave the engine some rpm).
I tryed the other way and the idle went down to allmost dead , BUT NO NOISE AT ALL....purring like a cat.
I took a test drive and discovered that the engine had no power at all , and no noise at all !!
I live in Greece and I believe that these so-called mechanics just steal my money , i'm fed up with this car , it has become a nightmare.
Has anybody a clue on what the problem is ????
PS: sorry for my bad english

[racerx]

Did you rebuild the engine yourself or did a mechanic do it for you?  If a mechanic rebuilt it, there should be a guarantee of some sort.  Also don't move the distributor unless you know what you are doing.  You can mess it up some more.  Do you even have a timing light?  Maybe you can post a video of the car running while the knocking happens so that we can get a better idea.

[datzenmike]

The engine needs a timing light to set the ignition timing. Or adjust the distributor until the pinging noise just disappears when accelerating. Make sure that  both coils are firing first though. Idle may drop so adjust the idle speed screw to bring it up.

 

Mechanics are in business to make a living. Don't work four hours to pay him for one hour of work. Learn how to do this stuff yourself.

[ari falco]

I went to my nissan dealer today , asking the mechanic to listen to the engine when revving it up to the point when it rattles/knocking , he was 100 % sure that the noise was from the valves.

I checked the valve clearence and they are according to spec.

The cam/chain alignment  does not seem to be right , I do not know how important it is for the engine to function properly and that may be why I have noise in the engine and that I can not get the timing / idle right.

I put the nr 1 piston at TDC and took some pics of the sprocket and chain , it seems fuc... up , the links and position dont seem to be as described in the manual .

The strange thing is that the car has worked for a year, but with rattling / knocking in the engine, and without idle speed and ignition timing  set satisfactory.

The mechanic who did the job on the engine says it does not matter so much where the marks and links end on camsprocket.

He insists that the ignition timing is correct. I will however replace the timing chain my self this time and according to the manual , There is enough material in this forum to do it my self.

Sending pics from camsprocket/chain : https://www.flickr.com/photos/144233655@N04/

 

PS: the nr 1 piston is att TDC when i took pics.

[racerx]

Do yourself  a favor and get a timing light.  They don't cost that much and it does not matter if the mechanic insist verify the timing. Also where does your rotor point to when you say it's at TDC?  Don't replaced, move, change anything until you verify that's the problem.  One step at a time.  You have not verified the basics and you are already planning to replace to timing chain.

[datzenmike]

Valve clearance does not change when revved up. If it only makes noise at a certain rev it isn't the valves. Valve noise will be constant it only speeds up.  

 

Wrong the cam timing is important for proper running.

 

Set TDC by turning only in the clockwise direction up to TDC. Do not back up to set. If you overshoot the TDC mark, back up 1/2 a turn counter clockwise and repeat. May take 4 or 5 tries. If the cam sprocket is off you can change this yourself BUT know how to block the timing chain tensioner so it does not fall out while doing this procedure. It will save you 4-6 hours of extra work.

 

 

Yes you can do this yourself and your mechanic probably has never worked on a Z24 before so you know as much as he does. Doesn't make much sense to work 4 hours to pay for one hour of his time to learn about them. 

 

 

Make sure both coils are firing.

[ari falco]

Hi Mike !! 

My problem with the z24 persist and driving me crazy..!!

I have not had much time to explore more what might be the problem,, but here it is :

Nissan hardbody, 4x4 , z24 carburated , 1990 , valve lash OK!, The carburetor is ok!, No vacuum leaks,single spark , new timing chain and tensioner , (double row chain).

New pistons, new cylinder head and gasket ,(AGAIN...) !!

I hear a rattling sound from the engine between gear changes or when I ease on the throttle, it sounds only when the accelerator pedal is in some kind of intermediate position, not in pull or engine braking mode , and Always after 2000 rpm.

(ignition seems to be ok, have not checked with a timing light)

If I screw the distributor to the end against the engine the rattling stops  , but then, the engine has less power and low rpm on idle , and when i connect the vacuum to the dizzy it starts rattling again.

If I screw distributor to the end of opposite direction,(from the engine), increases the rattling noise but with a normal motor power and normal idle speed.

In any case, it sounds only when I have the accelerator in an intermediate position, not under load.

can it be that the compression in one of the cylinders is not as it should be?

Sparkplugs ??,, ignition coil ??....i don't know what more to think of ..  :(

[datzenmike]

You have single spark plugs???? We had two plugs per cylinder.


Have the timing checked and set properly. I don't know what it would be for a single plug engine. Too much ignition advance is NOT GOOD for an engine and can cause detonation and damage.

[ari falco]

You have single spark plugs???? We had two plugs per cylinder.

 

 

Have the timing checked and set properly. I don't know what it would be for a single plug engine. Too much ignition advance is NOT GOOD for an engine and can cause detonation and damage.

The problem with the engine and the noise is probably , (99.9 %) , that the cylinder head was milled down/resurfaced too many times.

I spoke with the former owner and was told that the cylinder head was resurfaced at least 3 times in his possession ,(and 2 times in my possession), it explains the problem.

I will of course buy another cylinder head, Used obviously because new is too expensive, but how will I know that this cylinder head does not have the same problem ?.

Is there a Resurfacing  limit point where you can see if  the head has reached its limits ??

[datzenmike]

 

(ignition seems to be ok, have not checked with a timing light)

If I screw the distributor to the end against the engine the rattling stops  , but then, the engine has less power and low rpm on idle , and when i connect the vacuum to the dizzy it starts rattling again.

If I screw distributor to the end of opposite direction,(from the engine), increases the rattling noise but with a normal motor power and normal idle speed.

 

 

 

You can look for another but first ...

 

Check the timing... should be 3 degrees before TDC. Too much advance will ping. If idle drops turn it up.

 

Check that both intake and exhaust side plugs are firing. BPR6ES intake and BPR5ES exhaust.

 

Use a higher grade octane gas.

[ari falco]

You can look for another but first ...

 

Check the timing... should be 3 degrees before TDC. Too much advance will ping. If idle drops turn it up.

 

Check that both intake and exhaust side plugs are firing. BPR6ES intake and BPR5ES exhaust.

 

Use a higher grade octane gas.

I've tried all that....(i have the 4 plug engine)...the only thing that remains is the head...according to nissan spec resurfacing limit is 0.2 mm ,(0.008 in)..both the cylinder block and head..0.1mm block...0.1mm head...after resurfacing the head 5 times and the block 2 times i think the limit is passed long ago,,,time to look for another head....

[datzenmike]

I can't know what you tried unless you follow up and let me know.

 

 

I'm familiar with the 4 plug head so the timing will be more than the 3 degrees I mentioned. Find out what the factory recommends for your engine and follow that. Milling the head will raise the compression and you may have to lower the compression slightly.

 

Five times???? Why was it resurfaced so much? and why the block surface? Almost never is this required.

 

Excessive milling will begin to affect the timing chain length. Cam and crank are now closer together. The chain tensioner may be past it's effective limit and the chain making the noise.

[ari falco]

I can't know what you tried unless you follow up and let me know.

 

 

I'm familiar with the 4 plug head so the timing will be more than the 3 degrees I mentioned. Find out what the factory recommends for your engine and follow that. Milling the head will raise the compression and you may have to lower the compression slightly.

 

Five times???? Why was it resurfaced so much? and why the block surface? Almost never is this required.

 

Excessive milling will begin to affect the timing chain length. Cam and crank are now closer together. The chain tensioner may be past it's effective limit and the chain making the noise.

Hi Mike !!

z24 , 4 plug , carburated .   The cylinder head and/ block surface have been resurfaced below factory limits , Is it possible to restore the valve train geometry  with head spacer shim ? , And if so, which solution is best ! copper/steel gasket closest block surface and the usual gasket on top, and use of sealant ??

[datzenmike]

Adding a spacer might work or maybe two head gaskets. I've never done this before.

[Crashtd420]

Ive heard issues with the copper ones, mainly sealing.. 2 head gaskets scare me personally .

There are some companies that make custom MLS headgaskets with different thicknesses to suit.... I think cometic was one company.... if they have a stamp for it already there not too bad on price maybe 100 or so.... custom can get up to 250...

[datzenmike]

Usually copper is for SC and turbo applications or hi compression where the head has to come off often. Likely there would be sealing problems.

 

He's in Greece so availability is iffy. You can easily make a copper gasket.... Two head gaskets would compress to about 2.5mm thick. 

[Eric flemming]

Sounds to me like you have a connecting rod barring bad or lose. I had the same problem sounded like timing chain but it's not. Old mech way of checking where the noise is coming from! Is to take an old wooden broom stick put one end to your ear the other end on the engine near the oil pan start from front to back and lessen for the noise! bet to one number 3 connecting barring bad. It might help if you have some one rev the engine up to hear the noise. The engine I have needs to be rebuilt.  I put new mains and rod barring's in mine. Also found out that these engines are known for oil starvation on the barring's.  But they are the closest to a 100 hp your going to get. the newer engines are less. These are die hard engines. good luck.

[Eric flemming]

check the rear MAINS!!!! They could be jumping up and down! Get your book out drain the oil and pull the pan. Start becoming your own mechanic.

[datzenmike]

Won't be a main bearing.

 

These engines are not known for oil starvation, they are basically an up sized L series with the same main and rod bearings and oil pump.

 

The next gen truck engines KA24E and KA24DE were 140 and 150 HP or 50% more than the Z24.

[Eric flemming]

Question? Dose that year come with the crank Poisson sensor? On the side of the block if it is bad or worn out it will send bad info to the computer affecting the timing. like the dodge neon has a disturber on the cam but gets it signal from the crank sensor. 

[datzenmike]

The late 720 and early D21 Hardbody had the Z24i engine which had a CAS. The CAS was almost exactly like and in thew same position as the distributor. It was driven off the crank. The CAS is much improved over the distributor it replaces. The old distributor had a slot and a screw driver like blade that fit into it. It  is sloppy and not that stable. The CAS used a spline and even the later KA engines used this. 

[ari falco]

Well ...after a good history search on my engine ,(z24 , straight-four , carburetor, 8 valve , sohc , breaker point ignition , 4 plug) , one thing is clear.

The head and block have been shaved/milled too much , the head has probably,( i do not know for sure), been milled at least 0.030in(0.76mm) and the block at least 0.010in(0.25mm) , as you understand i cant get the engine to work as is should , the engine starts and runs but not as it should.

 

Question is : does it help if i put a thicker head gasket ?? , i found one in Mexico,(ebay) for sale thats 2mm , (0.078 inch).

(https://www.ebay.com/itm/HEAD-GASKET-THICKER-THAN-NORMAL-FITS-NISSAN-ENGINE-Z24-/253218371187).

Or maybe a normal gasket with shim/spacer ??

 

ANY IDEAS ???

[datzenmike]

The numbers given will raise your compression to 9.0 and that's not going to stop it running. An increase in compression may need the timing retarded slightly.

 

What's it doing???

[ari falco]

I have tried everything , but not a thicker gasket.

I have chain slack whatever i do , it doesn't matter what mark i use on cam sprocket or how much i tightening the chain ,(there is a rattling noise) , but ONLY when i release gaspedal and keep the pedal on cruise mode , like something is loosening when i relese of gaspedal.

I beleave that the cam/crank timing is not where it should bee due to over shaving/milling , i can however make it stopp rattling if i turn the distributor in diferent positions , but then i dont have any power in engine or it pings like crazy.

 

crank bearings , pistons and rings, valves and sealings , camshaft , timing chain kit are all new.

[datzenmike]

The timing chain turns the same if floored or not. It isn't loose when you let off the gas. Check the exhaust pipe is not rubbing something when you let off of the gas. The engine torques fron side to side when you give it the gas and when you let off. Maybe an engine mount is broken.