Timing chain replacement dilemma

[ElliotV]

So I think my timing chain needs replaced on my 85 720 4x4. Whenever it starts up it clacks until the tensioner gets oil pressure and now when it's warm and I am in 1st 2nd or 3rd I can hear clacking like it's losing tension and slapping when I let off the gas a little bit and I am just putting around at low load(part of the reason I think it's the chain since it would in theory be under low tension during those times and this motor has 160k on it and I have no idea if it's been done). I keep and eye on my oil pressure and I think it's really good when it's not warm yet it's just above 45 at idle and halfway to 90 on the highway cruising about 2800rpm and warmed up it's at just below 45 at idle and at 55-60 on the highway. So all that said looking into replacing the chain I have to mess with the oil pan of course and it looks like a pain to replace the oil pan gasket.

 

When looking at replacing the gasket it looks like I might as well pull the engine I have to remove the diff crossmember and disconnect the steering and sway bar stuff. In addition I have to remove the engine from the engine mounts and lift up the motor. I was wondering if anyone could tell me if there is a way to avoid that. Can I just unbolt the pan and lower it enough to sneak the gasket around the pickup tube it will I really have to drop the front crossmember to get to it.

 

I am not super worried about doing the timing chain itself it seems pretty straight forward and I love this truck and would hate to have to rebuild a motor for no reason.

[ElliotV]

So I think my timing chain needs replaced on my 85 720 4x4. Whenever it starts up it clacks until the tensioner gets oil pressure and now when it's warm and I am in 1st 2nd or 3rd I can hear clacking like it's losing tension and slapping when I let off the gas a little bit and I am just putting around at low load(part of the reason I think it's the chain since it would in theory be under low tension during those times and this motor has 160k on it and I have no idea if it's been done). I keep and eye on my oil pressure and I think it's really good when it's not warm yet it's just above 45 at idle and halfway to 90 on the highway cruising about 2800rpm and warmed up it's at just below 45 at idle and at 55-60 on the highway. So all that said looking into replacing the chain I have to mess with the oil pan of course and it looks like a pain to replace the oil pan gasket.

 

When looking at replacing the gasket it looks like I might as well pull the engine I have to remove the diff crossmember and disconnect the steering and sway bar stuff. In addition I have to remove the engine from the engine mounts and lift up the motor. I was wondering if anyone could tell me if there is a way to avoid that. Can I just unbolt the pan and lower it enough to sneak the gasket around the pickup tube it will I really have to drop the front crossmember to get to it.

 

I am not super worried about doing the timing chain itself it seems pretty straight forward and I love this truck and would hate to have to rebuild a motor for no reason.

[datzenmike]

Don't make the mistake of thinking the timing chain is under more load just because you are making the engine work harder or not. All the timing chain does is turn the cam shaft against the resistance of the opening and closing valve springs. 2,000 RPM under full throttle or 2,000 RPMs while slowing down is the same to the timing chain.

 

Look for and eliminate other causes of noise. A good one is a blown exhaust manifold gasket between it and the head. Another is the gasket between the manifold and the down pipe. Still another is a crack in the manifold. Then there is the exhaust tube around the back of the head to the EGR valve on the intake. One more are the two tubes between the air filter and the exhaust manifold. Last is a leak in the catalytic converter under the driver. A small leak in any of these can cause annoying noise. As a rule these are louder under load that not but still noisy and sometimes they lessen when warm.

 

Loose valve lash is another clacking/tapping sound but it is loudest when cold and quiet or quieter when the engine warms up and the clearances decrease.

 

 

I would check your valve lash and inspect anything exhaust related. When engine is cold you can quickly run your hands over hard to see areas feeling for exhaust leaks before the parts get too hot.

 

[ElliotV]

Noted on the exhaust leak I will have to check for one and I do think there is one coming from after the cat as I can hear something between the cab and bed(I know it's weird but I tend to notice odd stuff sometimes) and it's not a exhaust style sound it sounds metallic. I will order a valve cover gasket and check the valve lash on it do you know the specs and what the exact procedure is for it on these.

[datzenmike]

Give the exhaust system a really good shake and see if it's hitting anything. Loose clamp?

 

Factory service manual says 0.014" on both but the earlier Z22 engine was 0.012". As they use the same valve train I would go with the quieter 0.012".

 

 

 

Nissan recommends that the engine be thoroughly warmed up to operating temperatures.

 

Set the engine to TDC on the compression stroke using the ignition timing scale and the notch on the crankshaft pulley. To confirm this, both intake and exhaust valves will be closed. If they are not you are on the exhaust stroke, so turn the engine one complete turn.

 

Adjust the following valves...

Both valves on number one cylinder

Intake on number two

Exhaust on number three

 

Turn engine ONE turn and back to TDC on the exhaust stroke

 

Adjust the following valves...

Exhaust on number two

Intake on number three

Both valves on number four

 

This avoids constantly bumping the engine and is extremely fast and you should be able to easily set the valves before the engine cools down.

[ElliotV]

Ok so set #1 to tdc then adjust the 4 valves then rotate 1 turn back to the timing mark and adjust those other 4. And I guess while I have the valve cover off I can look at the timing chain and sprocket and that can give me a idea on what's going on there.

[datzenmike]

There are two TDC. The first is the compression stroke on number one where the first four valves are set. You rotate the engine ONE full turn and it comes up to the TDC on the exhaust stroke for number one and your set the remainder valves.

[ElliotV]

32 minutes ago, datzenmike said:

There are two TDC. The first is the compression stroke on number one where the first four valves are set. You rotate the engine ONE full turn and it comes up to the TDC on the exhaust stroke for number one and your set the remainder valves.

Yes that is what I meant I normally just call tdc when #1 is at the top of the compression stroke

[IZRL]

I have some rattles and clackity clacks that I've been trying to find as well. So far I've found and temporarily fixed the loudest rattle that was driving me insane. It would rattle the worst while driving. When parked the rattle was way quieter even when revving the engine. It would actually be a little louder after you revved it and released the throttle while parked. This made it really hard to find. The whole time I was looking for a loose heat shield or similar because that's kind of what it sounded like. after a couple weeks of having no luck. I finally just stuck my hand between the valve cover and the firewall and started shaking stuff and tapping things with my fingers. And bingo, it was the damn EGR tube. The EGR Tube is loose where it goes into the EGR Valve. When the tube vibrates it hits the walls of the egr valve and it makes a really loud clacking sound. You can shake the EGR tube all you want and it wont make a sound. Only way to make it rattle is to tap the egr tube with something. Tried to tighten the nut but it's seized. I just wanted the rattle gone asap, so I tide it down with some baling wire. Will be doing EGR delete soon. This might not be what's rattling on your truck, but I'm sure this will help someone at some point 🤠.

 

 

 

Edited January 26 by IZRL

[ElliotV]

32 minutes ago, IZRL said:

I have some rattles and clackity clacks that I've been trying to find as well. So far I've found and temporarily fixed the loudest rattle that was driving me insane. It would rattle the worst while driving. When parked the rattle was way quieter even when revving the engine. It would actually be a little louder after you revved it and released the throttle while parked. This made it really hard to find. The whole time I was looking for a loose heat shield or similar because that's kind of what it sounded like. after a couple weeks of having no luck. I finally just stuck my hand between the valve cover and the firewall and started shaking stuff and tapping things with my fingers. And bingo, it was the damn EGR tube. The EGR Tube is loose where it goes into the EGR Valve. When the tube vibrates it hits the walls of the egr valve and it makes a really loud clacking sound. You can shake the EGR tube all you want and it wont make a sound. Only way to make it rattle is to tap the egr tube with something. Tried to tighten the nut but it's seized. I just wanted the rattle gone asap, so I tide it down with some baling wire. Will be doing EGR delete soon. This might not be what's rattling on your truck, but I'm sure this will help someone at some point 🤠.

 

 

 

This is making me want to do a Weber 38/38 and completely delete this truck even more lmao it's definitely on the agenda. I will have to see if I can take a look at it this weekend or something and see if that is it but it really doesn't sound like it's in the engine bay but I don't have much experience with this truck and what sounds coming from where sound like. The weather has not been kind and it's been raining for the past week or so on and off.

[IZRL]

1 hour ago, ElliotV said:

This is making me want to do a Weber 38/38 and completely delete this truck even more lmao it's definitely on the agenda. I will have to see if I can take a look at it this weekend or something and see if that is it but it really doesn't sound like it's in the engine bay but I don't have much experience with this truck and what sounds coming from where sound like. The weather has not been kind and it's been raining for the past week or so on and off.

I actually jumped the gun and purchased a weber 38/38 without doing much research.  Once it arrived I started doing more research. From what I gathered from other peoples experience is that the 32/36 is better suited for a stock engine, daily driving stop and go traffic, and for better fuel efficiency . The people who I read were happy with the 38/38 are the ones that had modded/built engines. One of the key things I didn't know about the 38/38 when I first ordered it was that both the primary and secondary barells are open at all times which means you can kiss any kind of decent gas mileage goodbye. I wrapped that puppy up and shipped it back and ordered the 32/36 that uses only primary at low RPMs and only opens secondary at higher RPMs. This puppy runs like a dream and it runs strong. I let my buddy who sold me the truck drive it. And he said it felt like a different truck (not sure how good the oem carb was running when he had it tho). I'm sure it's not a big HP upgrade but it's enough to be noticeable. But don't take my word for it. All I'm saying is do your research on the two carbs and see what suites your short term/long term plans for the truck. I paid for shipping 3Xs when it was all said and done hahaha and its not like its a cheap carb either. If you have the money to throw around than I would recommend a weber. I personally would've stuck with the OEM carb if it wasn't broken beyond repair.

Edited January 26 by IZRL

[datzenmike]

The stock Hitach is very complex but the best over all for drive-ability. The 32/36 is next but you do have to actually drive it as the secondary will tip in at about 60% throttle. Gas mileage is dependent on how you drive it but on the plus side, it has a small power increase. The 38/38 is a V6 or small V8 carburetor and will work on a 2.4 but requires an even gentler foot to not tip it in too soon. If you don't care about mileage and drive-ability and want more out of your 2.4 then a 38/38 is a good idea.

 

Drive-ability: is the ease of use of a carburetor. Simple to drive, good starting and restarting when hot, idle, throttle response, emissions, mileage and performance. For that the stock carburetor is best but like I said it's complicated.

[ElliotV]

1 hour ago, datzenmike said:

The stock Hitach is very complex but the best over all for drive-ability. The 32/36 is next but you do have to actually drive it as the secondary will tip in at about 60% throttle. Gas mileage is dependent on how you drive it but on the plus side, it has a small power increase. The 38/38 is a V6 or small V8 carburetor and will work on a 2.4 but requires an even gentler foot to not tip it in too soon. If you don't care about mileage and drive-ability and want more out of your 2.4 then a 38/38 is a good idea.

 

Drive-ability: is the ease of use of a carburetor. Simple to drive, good starting and restarting when hot, idle, throttle response, emissions, mileage and performance. For that the stock carburetor is best but like I said it's complicated.

I might go with the 32/36 then when I eventually mess with the carburetor cause I do want a power increase so I am not nearing full throttle when I am driving down the highway trying to just keep up with the speed limit 

[ElliotV]

10 hours ago, IZRL said:

I have some rattles and clackity clacks that I've been trying to find as well. So far I've found and temporarily fixed the loudest rattle that was driving me insane. It would rattle the worst while driving. When parked the rattle was way quieter even when revving the engine. It would actually be a little louder after you revved it and released the throttle while parked. This made it really hard to find. The whole time I was looking for a loose heat shield or similar because that's kind of what it sounded like. after a couple weeks of having no luck. I finally just stuck my hand between the valve cover and the firewall and started shaking stuff and tapping things with my fingers. And bingo, it was the damn EGR tube. The EGR Tube is loose where it goes into the EGR Valve. When the tube vibrates it hits the walls of the egr valve and it makes a really loud clacking sound. You can shake the EGR tube all you want and it wont make a sound. Only way to make it rattle is to tap the egr tube with something. Tried to tighten the nut but it's seized. I just wanted the rattle gone asap, so I tide it down with some baling wire. Will be doing EGR delete soon. This might not be what's rattling on your truck, but I'm sure this will help someone at some point 🤠.

 

 

 

I look at that tube this morning and tried wiggling it around and tapping on it and it's definitely not it cause it is in there tight and won't move and just makes a almost hollow sound when I tap on it

[NC85ST]

No, you don’t have to remove the pan to replace the timing chain, if you’re pulling the head. Just remove the bolts from the pan that hold the timing cover and do your best not to damage the pan gasket under the cover. I would be surprised if the chain needs to be replaced at 160,000 miles, unless a previous owner has been in there and really messed things up. I had a z24 that I put 400,000 miles on and the chain was fine, can’t say that for guide’s though. 

[ElliotV]

9 hours ago, NC85ST said:

No, you don’t have to remove the pan to replace the timing chain, if you’re pulling the head. Just remove the bolts from the pan that hold the timing cover and do your best not to damage the pan gasket under the cover. I would be surprised if the chain needs to be replaced at 160,000 miles, unless a previous owner has been in there and really messed things up. I had a z24 that I put 400,000 miles on and the chain was fine, can’t say that for guide’s though. 

Well that's what I am mainly thinking is messed up is the guides. Cause when I start it up and it doesn't have oil pressure it clacks and I took it to the same rpm range before it stopped clacking it made the same sounds I am hearing. The previous owner did mention to me that when I start it and there is no oil pressure it does that which is true but when it's warm it does it as well now. Could it also be a thing with the oil cause there is the slightest smell of gas in the dipstick and I have about 3000mi on this oil change so I am wondering if the oil has thinned up. I am running 10w-30 synthetic with no additives. Should I run a thicker oil and/or zinc or something else. And I figure when I check the valves it will let me look at the chain and gear which should be able to give me a idea of what everything else looks like.

[datzenmike]

You can run Shell Rotella T6 which I believe is a synthetic oil but it is an over kill for oil on a more that 20 years old engine design. Rotella T4 is also a high ZDDP oil and comes in 10w30 and 15w40. When your engine was new the ZDDP anti scuff additive was over 1,000 ppm. Since '92 it's been slowly reduced to around 500-600 PPM today. Rotella is 1,200 PPM so I recommend it.

 

I've measured the tensioner diameter and at 55 PSI the tensioner applies only 7 or 8 pounds of force on the chain. At idle this will be about half that so I don't think it significantly does much. The spring behind the plunger is extremely stiff as anyone who has put one in will testify. If there is any noise it's the chain slapping against the the tension and slack side guides. These are nylon? coated and it will wear away.

 

Gas in the oil... Check that the fuel level in the float chamber is at a half way mark and that the choke is working properly and is opening fully within 10 min or less. Short trips where the choke is on most of the time will dump a lot of gas into the oil. Never hurts to take for a longer weekend trip. Engine heat will evaporate the gas in the oil.

[Foxhound]

I'd been trying to chase down a rattle as well and it turned out to be the choke plate. There's a little bit of play parallel to the shaft it connects to and at higher rpms it's obvious with the air filter housing off. Easy enough to check while you're in there. Was driving me crazy.

 

I just got a weber 32/36 I'm about to put on once some more parts arrive. This Hitachi is pretty beat up and has been neglected by previous owners. Might try to rebuild it and sell or keep in case I want to revert back to OEM at some point.

[ElliotV]

I still think it is internal because it doesn't make noise after the oil light goes off when I start it up and it only does it after the oil has thinned up but I did change the oil with 10w-40 and added zinc and it has quited  down but still does it under a low load condition at constant rpm

[datzenmike]

How long till the oil light goes off?

 

What is your hot oil pressure reading at idle?

[ElliotV]

On 2/7/2024 at 8:38 PM, datzenmike said:

How long till the oil light goes off?

 

What is your hot oil pressure reading at idle?

Hot idle is just below 45 maybe 35-40 which I figure is good(this is also after driving around town for nearly an hour. Oil light goes off a couple seconds after it fires up. 

I took the valve cover off this morning because the sound became slightly constant or I was going insane or both. Timing chain looks to be replaced it's really tight and is a double roller and looks really good. After I put the valve cover back on it's stopped doing it when it starts and isn't as bad when driving and my dad drove and thinks its something rattling on the exhaust and I think it's in the EGR system cause it does seem to sound more like a echo and not a thud like a bad bearing and the cam looks good and all the valves seem to be straight and don't move at all so the valve guides are good.

[datzenmike]

I see you have two post about basically the same thing. Might be a good idea for me to merge them into one so answers are not duplicated or someone on one post doesn't know what you've tried on the other.

[ElliotV]

Yeah accidentally posted twice and couldn't delete the other one 

[datzenmike]

I'll check them over for content and add them together.

[ElliotV]

ok for anyone having a similar issue this is what I have found. The oil pressure thing has nothing to do with the sound I am hearing as far as I can tell. 

 

I know the sound I am hearing is coming from the exhaust it is possibly detonation or has something to do with the miss I sometimes have at idle(also backfires when engine braking sometimes) but the sound is exactly in sync with the exhaust notes and I can really hear it when I am parked next to something. At some point I am probably going to look for a header and redo the exhaust system meaning cat and egr delete since I dont have inspections in my state since I am assuming something has fallen apart in the cat or the 02 sensor and is now rattling around and just echoeing in the exhaust.