720 cam, lifter, head questions.

[Awkyeow]

Ok. 

I have a ticking noise I can not get rid of with a valve adjustment. I have done this 4 times just to make sure all was done correctly. 

The noise is better but I am not satisfied that this is how it should sound. I remember the engine being much much more quiet back in 87. Granted it was pretty new.

I want it back to if not as close to new as possible. Cylinders 3&4 have a lower compression that adding some oil raises the numbers, so, Rings. Going to do all the rings soon.

So, I know nothing about the engines specifics and what differences there are for the Z24 engines through the different years.

I have picked up a rebuilt head for an 86-89 Z24 stating Vin N & S. Mine is a Vin S for the 8th character. No idea what this means? The guy who sold me this said it should work. I probably should not have bought it. But it did. I believe this is compatible for the 86 z24i. So I took a chance and picked it up. Thinking this should work for my carbed 84. Thoughts?

The cam is stamped 382 on the sprocket side. 

1. Will this cam work for my current stock motor?

2. Will these rocker arms/lifters work for my engine if I just swap out the top lifter rack.

(Just to see if it sounds different with different parts on it) Trying simple first.

3. Will the actual head(casting) work with my engine? Stamp #'s are different than mine. (The ones that are on top back passenger side where the cover gasket goes, what do these mean)

(It is also stamped 10W like mine is. The circles next to the 10W look different than mine do. What do these mean?)

 

20240219_142359.heic20240219_142335.heic20240219_142418.heic20240219_142555.heic20240219_142624.heic20240210_162254.heic20240219_142305.heic20240219_142458.heic

[datzenmike]

What valve clearance are you using? My FSM says 0.012" set HOT.

 

3&4 low. These are adjacent cylinders and the Z24 is well known for blowing it's head gaskets. If blown between 3 and 4 the compression will seesaw back and forth giving a low number.  A leak down test would confirm. Set to TDC on #3 (both valves closed) and add air pressure. If leaking into #4 (valves both slightly open) you will hear a hiss if you listen at the carburetor inlet. If a head gasket, about $30, that's a lot cheaper than a rebuild which would fix the problem but only because a new gasket was used.

 

The Z24 was used from '83-'86.5 only in the 720 and has almost no differences. After April '85 a Z24i was offered which had throttle body fuel injection. The '86.5-'89 D21 Hardbody also used the Z24i but a lot of the throttle body parts won't interchange with the earlier Z24i.

 

 

The 8th VIN character is the engine size. N may be for the Z24i and S for the earlier non EFI Z24. The engines will otherwise be the same. I had/have a Z24 engine from a '84 720 but when I pulled the engine the flywheel had crayon saying D21. So this Z24i was put in that 720 and the intake, distributor and carburetor changed. It worked very well.

 

13001-W0480 is the Z24/Z24i cam.

13001-W0483 is the Hardbody Z24i cam

The 80 and 83 in the part number refers to the distinction code that identifies differences in parts that are similar. Both 80 and 89 refers to the material used. And this could mean a different metallurgy or compound used even though the cam specs are identical.

 

The 720 Z24/Z24 head casting number is 11041-10W00. The Hardbody head has a different number but this may be a redesigned placement of the temperature sensor Likely beside the exhaust side #1 plug for the EFI. Sensor NOT the sender for the heat gauge.

 

 

 

 

 

 

[Awkyeow]

Thank you!

So the head itself will work on my engine. As it says 10W.

 

I will try the leak down test tomorrow. So instead of adding oil, put the air in the plug hole and listen if any air comes out? Can I assume there should be no hiss if the valves are closed properly? Probably some back pressure out the same plug hole because it has nowhere else to escape from? If all is working correctly.

I did add some oil in the cylinder and the pressure went up. I did this for both 3 and 4 separately.

If the head gasket was blown would the compression numbers still go up after adding the oil in the cylinders?

The engine runs good, no smoke at all at tailpipe, passed smog with great numbers.

The engine is old. I want to rebuild it the best I can. This is not primarily the issue I am worried about. I will take the head off soon and replace the crankshaft bearings and see if anything else is worn out.

 

My main issue is the head noise.

So the rockers are the same all across the years on the Z24?

Same with the camshaft?

I adjusted all the valves to .012(hot)

 

I basically would love some conformation that swapping the top rocker arm assembly from the newer one to mine won't screw up my engine. Just to see if the noise goes away. Doubtful, but an easy attempt before I go deeper into the head.

 

The cam says 382 stamped on the face where the pin is.

Is this a stock cam?

[Awkyeow]

As well, would the rings/head gasket issue cause the ticking noise in the head?

 

I also felt a slight vibration when slowly raising the rpms by hand at the carb. I could feel it against my legs while leaning against the truck.

It is only at a very low rpm then it goes away. Could this be something out of balance or worn crankshaft/bearings/piston/piston rod? I do hear a slight knocking. It is very faint, but it is there, seems to be coming from the rear of the engine. Now again, I will be replacing all the timing chain stuff while I am in there.

Has a slight chain noise too. But not too bad.

Exhaust is 100% new so I can assume the ticking is not an exhaust leak. The noise was there before i did the exhaust.

Timing is set to °3 BTDC.

or very close to it. Timming mark does not bounce around, it is very still once set.

 

Another thing I noticed was that the oil sitting in the head itself looked very dark. But my dipstick oil is golden. Why??

Could it be a bad oil pump?

Pressure does go up when I rev or drive. I have the stock gauges with the center console.

 

During this rebuild I am going to have the tranny worked on. So I will replace the crankshaft bearings since the tranny will be out.

 

I know, lots of questions.

I just know you all have much experience with these engines.

My apologies for so many questions.

[datzenmike]

Looking back there were three part numbers for the Hardbody head. I was looking at the latest supersedence number. 10W00 does cover all the Z24i engines.

 

Did you say it quieted slightly when you set the valve lash?

 

Rockers and cam should be the same. I would change the entire head. It's not a good idea to run a mixture of rockers on the same cam lobe. When the head is off you should be able to tell if the head gasket was bad. 

 

In addition if the head is off it would be a good time to change the timing chain, sprockets, guides and the chain tensioner.

 

Dark oil might indicate that there isn't much oil exchange on the valve train. Are the rocker arms wet with oild? What hot oil pressure at idle? A tired engine should have 20 PSI and go to around 55 when revved and held there.

 

Before removing the cam sprocket be sure you know the procedure for blocking the timing chain tensioner from falling out if not replacing the chain.

 

[Awkyeow]

Yes, it did quiet the noise down a bit after valve adjustment. It comes back though, and it is still too loud for me.

The valve noise isn't there during warm up. Could the ticking be a vacuum issue?

 

I don't have the oil gauge in the truck at the moment, but those numbers seem to be about where mine are at. The head seemed to be a bit wet but not too saturated. To me, the unprofessional logical eye, it doesn't look right. Shouldn't the oil be the same color as what is in the pan?

It looks burnt in the head areas. The puddle in the middle of the head is dark. No puddles anywhere else near the sides. Just in the center areas. I will pay more attention the next time I take off the cover.

The dipstick oil is like honey, so it seems weird to me that the head oil looks dark.

 

 

Ok then,

I will do the leak down test today. I don't suspect a headgasket issue. Never entered my mind. Oil test suggests rings. But I am not a professional.

 

So if air comes out of the sparkplug hole #4 while testing #3, obviously there is a gasket leak.

If air or hissing  comes back out the carb there is a valve issue. So a valve sealing issue would mean worn lobes, valves, springs, rocker arms themselves?

I guess, that is the reason I want to replace everything with new. Logically it shouldn't sound the same if I replace all the parts.

 

Do you just put a wedge down in between the chain to keep the tension? Or put a long prybar like thing down to apply pressure to the tensioner, I don't remember.  It's been awhile.

 

But yes, when the head comes off I will replace everything I possibly can. I am not ready for that just yet.

I still want to drive it a bit. It just got back on the road 3 weeks ago, after it has been sitting for about 15 years.

 

Just to make sure we are on the same page. 

I have an 84 Z24 720, not a Z24i hardbody. I am sure you already know this. Though I hate to assume anything.

The head i bought was listed for an 86 Z24i 720 compatibility.

I took a chance that it would work on the 84 Z24 720.

 

So the rockers and camshaft are the same for both Z24 AND Z24i?

 

Bummer, I wanted to swap out rocker rack just to see if there would be a noticeable difference in sound.

I won't do that now if you do not recommend it. I will just swap out the entire head and see how it runs.

But I will have to wait on that because I am not ready to tear the truck down just yet.

Is the 382 marked on the rebuilt camshaft the factory lift or duration?

 

Thank you again for your expertise!

[ElliotV]

I am not datzen Mike but if I were you I would go ahead and replace the timing chain unless it looks really new it's like 50 bucks for a timing chain set with a new tensioner and everything from dnj and good insurance.

 

As for the leakdown test I think what they meant by leaking out the carb is when both valves are closed on 3 then 4 will be slightly open and you can hear that hiss

 

And from what I have found looking at parts and stuff the only main difference between the z24 and z24i is the ignition system and the intake other than that should be pretty much the same

[datzenmike]

Warm up the engine and shut off. Take the valve cover off and remove both coil wires from the distributor cap so the engine will not start. Have someone turn the engine with the starter while you observe the valve train. After 5-10 seconds there should be oil oozing from the sides of each rocker arm. I know the L series has oil pressurized in the hollow cam that is spinning throwing oil everywhere. The Z24 shouldn't do this as the oil is inside the stationary rocker shafts... so you can try with the engine running at idle. You mentioned that there seems to be a lack of oil. 

 

If doing a leak down test then the test cylinder valves will be closed. If you hear air hissing in the carburetor then the valve is not sealing. I doubt you will hear air at the long end of the tail pipe. Perhaps unbolt the exhaust manifold and move out of the way.

 

 

Leak Down test.

 

There are different types of testers but the one below you set the supply pressure to 100 PSI and the other gauge reads the pressure in the cylinder. It will always be less. If the cylinder reads 85 then that's a 15% leak, a pass, barely. The less leak the better.

 

 

If an adjacent plug hole hisses then gasket is blown.

 

If hissing at the  valve cover vent hose then air is getting past the rings. Which is normal to a certain extent. If one cylinder is markedly louder there may be a ring problem.