720 timing chain rattle fix?

[Awkyeow]

Hi there,

I have have an 84 720.

I remember someone had a fix for the self chain tensioner on these.

I read this maybe 10 years ago?

Is there some kind of modification I can do when I swap out timing chain and all parts related? I have done this once with no modifications and the noise was still there after the install.

I am thinking of adding a spacer either inside where the spring is, hoping to add more tension to the spring and/or adding o rings to the outside shaft of the tensioner so it does not go back in as far. As well, elongate the mounting holes in the brackets to push the chain a bit more in, to increase tension on the chain.

Any advice or knowledge of a modification would be greatly appreciated. This truck used to run soo quiet. Going to rebuild the head next. Quiet down the tapping.

I replaced everything under the hood and the truck passes song with flying colors. New exhaust and cat as well. Runs good for its age.

This motor is one of those 30k mile Japan crate motors I had installed back in the late 80's. It was silent.

I really want it back to being silent.

Thank you for everyone's time.

✌️

 

[Awkyeow]

I would like to add that this truck has been sitting since 2013.

I have had it since 1987.

It has had 1, maybe 2 times a blown head gasket since late 80's and the head has been grinded down, not sure if that will make the chain slap a tiny bit more? Seems logical. This was 20 years ago.

Chain has always been a little noisy for awhile.

I started working on the truck again about 6 years ago. It ran fine but never was able to pass smog. I remembered a ticking noise that used to be coming from the carburetor that has been missing for many years. The air/fuel solenoid was faulty. I ordered one and put it in the carb. Ticking noise is back, this is a good thing. I rebuilt the carb.

New exhaust and cat.

A few years prior in 2018 I swapped out all the smog stuff. Everything is new. My intake manifold was so clogged at the egr valve area. No wonder it never passed smog. Egr valve was stuck and it was so clogged. Now that all is replaced with new and carb is tuned and working properly it LEGALLY passed smog for the first time since the 90's. I actually got a bit teary. This was last month. The tech said the numbers are so good you could suck the tailpipe... lol. Jokingly. I was shocked.

I have had my fair share of problems and trouble shooting, believe me. Still am... lol.

It isn't perfect, but I am happy where it is at the moment. I still can't drive it yet because it has been in non op for so long it will cost a good amount to pay back personalized plate fees that can only be paid if taking out of non op and paying the registration. Unfortunately my Registration is due in January. Because of their rules I have to wait until February 1rst so I don't get stuck paying for this year's registration fees,  then in January pay next year's fees. I would be paying double registration fees if i want to drive it now. Feb 1rst I am good which is weird because I will technically be late for a January payment. Anyway.

Any help would be great for getting more tension on the chain.

Tricks or tips.

[datzenmike]

First thing is check and adjust the valve clearance. One that is too loose will clack loudly. Warm engine thoroughly. Quickly set to TDC compression stroke on #1. Adjust both #1 valves, intake valve on #2, exhaust on #3 and none on #4. Turn engine ONE revolution and adjust the exhaust on #2, the intake on #3 and both valves on #4. Done, and before the engine cools off. Set all to 0.012" hot.

 

 

The tensioner is fine as is. Most timing chain noise is from worn timing chain guides. When the plastic wears off it's metal to metal. There are kits that include a new tensioner as well as the guides, chain and sprockets.

 

Yes ovaling the top hole on the right or slack side will allow the guide to be pushed inward toward the center before tightening in place. Push the new tensioner in all the way, push the slack guide over as far as it will go and then tighten it in place. Renewing the guides should fix the noise.

 

 

[datzenmike]

The preventative for the Z24 blowing head gaskets is as follows...

 

Head gasket

Once a year, on a cold engine, loosen one head bolt fully and immediately torque to 60 foot pounds. Only then loosen the next bolt. You can do this in any order or pattern you like. This is the only think I know of that will keep a proper clamping force on the entire gasket.

 

 

EGR

The EGR you can simply remove and wire brush off deposits.

 

 

One other thing I've heard over the years is that with the Z series engines when the get noisier, it's time for an oil and filter change. I know, makes little sense but it's been reported that after an oil change their engines were quieter.

[fredT]

One other thing I've heard over the years is that with the Z series engines when the get noisier, it's time for an oil and filter change. I know, makes little sense but it's been reported that after an oil change their engines were quieter.

 

Due to the fact that the chain tensioner is hydraulically tightened by engine oil pressure?

[datzenmike]

The spring is incredibly stiff to install and provides the tension. There is a tiny oil jet in the back of the tensioner mostly for lubrication. I worked out the effect of oil pressure on the diameter of the plunger once. At 50 PSI it amounted to about 7 pounds and much much less at idle oil pressure. Some of that oil will squeeze out and lube the chain. Could be.

 

[DwayneOxford]

Hadn't had mine long when chain began rattling. It was getting near the "low" on dipstick, needing oil change soon, wasn't gonna top up off till I changed oil. For some reason decided to top it up. Chain rattle, I don't understand why,  disappeared. Try overfilling a tad and see what happens. 

[Awkyeow]

Thank you for the advice everyone.

 

Will a thicker oil cause the chain to make more noise. When I was a kid the chain noise was bad and I started using valvoline racing oil 50w.

I know it is not the correct oil for the truck but it did seem to help a bit. Do you think the thicker oil is not helping or getting into the tensioner or oil ways? What oil do you recommend. Oil is pretty much new. Been sitting for awhile but literally no more than 100 miles on it.

 

EGR was far too gone to clean. Frozen. The entire area was caked with black carbon. Mostly clogged. All clear now. This truck isn't a daily driver and never will be again. Instead for here and there cruises.

 

I have done valve adjustments a few times. The ticking noise was still there. I know it will tick but it shouldnt be this loud. It's not over loud, I am just trying to get her back to almost new conditions, if possible.

I was thinking about a minor rebuild on the head. Replace rocker arms and springs when I redo the timing chain. I want to avoid taking the head off for now if possible.

 

[RyanC]

Years ago I rebuilt a L20b and not long after had a very noisy timing chain, anyway eventually we pulled the timing cover off and found that the oil passage was full of gunk and there was no oil pressure to the tensioner.  The block had sat for a long time and we had cleaned it as best we could, these days it would of been acid dipped but after a clean and new tensioner it was all sorted and quite again.  Just a thought.

[Awkyeow]

Thank you for the info.

When I do the chain replacement I will try to clean out the oil galleys and blow some air through them.

Is there a good way to ensure all the galleys get cleaned properly without removal of the engine?

I feel if I get the same results constantly after every chain and parts replacement and value gap adjustments then there is possibly something else I need to do or change out. Like too thick of oil is working against me?, or replacement of head parts. Compression is good.

[datzenmike]

 

3 hours ago, Awkyeow said:

Thank you for the advice everyone.

 

Will a thicker oil cause the chain to make more noise. When I was a kid the chain noise was bad and I started using valvoline racing oil 50w.

I know it is not the correct oil for the truck but it did seem to help a bit. Do you think the thicker oil is not helping or getting into the tensioner or oil ways? What oil do you recommend. Oil is pretty much new. Been sitting for awhile but literally no more than 100 miles on it.

 

        

You select your oil depending on the expected lowest temperature you expect before the next change. Colder is thicker and you want it thin enough to immediately get to the bearings when you start cold. The second number is the viscosity when hot with 40 being thicker than 30 and 50 thicker than 40 as long as the temperature doesn't get too low.

 

The first number is the viscosity when cold so if going to below -20F BUT not above 60F then you can use a 5w30. But I would not use this for prolonged higher speed driving on the highway. If not below 0 F then a 10w30, or 10w40 is fine. If not going below freezing then 20w40 and 20w50 can be used but the higher the second number the thicker the oil when hot and this will eat away at your mileage. I would use 20w50 if sustained +100F.

 

 

 

1 hour ago, Awkyeow said:

Thank you for the info.

When I do the chain replacement I will try to clean out the oil galleys and blow some air through them.

Is there a good way to ensure all the galleys get cleaned properly without removal of the engine?

I feel if I get the same results constantly after every chain and parts replacement and value gap adjustments then there is possibly something else I need to do or change out. Like too thick of oil is working against me?, or replacement of head parts. Compression is good.

 

Best preventative for clean oil galleries is to change your oil and filter on time.

 

 

I urge you to look up the ZDDP controversy. Since '93? oil makers have slowly been reducing the anti scuff additive ZDDP in their formulae from over 1,000 ppm to 550-600 ppm. This is because today's cars are designed differently and do not need this much protection. It's also poison for today's catalytic converters. Your truck was designed to run on oil made in the 80s that had 1,000 ppm or more ZDDP. Now the oil makers say that this new formula is reverse compatible with older engines but I'm not taking their word for this. My cam and rockers are basically priceless and irreplaceable. The good news is you can run 'racing oil' which is not subject to this change, you can buy ZDDP and add it to your oil or if you're like me simply walk down the aisle to the diesel oil section and buy Shell Rotella T4 in 10w30 or 10w40. Simple and cheap. Rotella T4 has 1,200 ppm ZDDP and I get a good night's sleep not thinking about this..

[Awkyeow]

Any current part #'s or info to replace all the rocker arms and springs in the head?

Are they the same rockers for exhaust and intake sides?

Thank you!

@datzenmike

[Awkyeow]

 

Here is a video of truck at idle with noises. Hard to hear, it is much easier to hear in person.

 

https://drive.google.com/file/d/1IEiEDcn9ITj431ryzHqk5pWeDWIofFTz/view?usp=drivesdk

[Crashtd420]

Try looking here....

 

https://www.nissanpartsdeal.com/parts-list/1984-nissan-720_pickup/engine_mechanical/camshaft_valve_mechanism.html

 

It's all oem... you can even bring the numbers to a dealer, you may get lucky with some things. But they probably have to order it in from a warehouse..

I find this site has good prices and diagrams...

[datzenmike]

1 hour ago, Awkyeow said:

Any current part #'s or info to replace all the rocker arms and springs in the head?

Are they the same rockers for exhaust and intake sides?

Thank you!

@datzenmike

 

No no no. No need to replace anything. The rocker clearance is adjustable. If a rocker is ticking loudly the clearance is most likely too much. The correct clearance is 0.012" when HOT. 

 

 

As for thicker oil, if the chain guides are worn away it's metal on metal and oil won't stop this. Check your valve clearances first. Timing chain kits are  $100 at least and if a rocker is out of adjustment it's all for nothing.

[datzenmike]

1 hour ago, Awkyeow said:

 

Here is a video of truck at idle with noises. Hard to hear, it is much easier to hear in person.

 

https://drive.google.com/file/d/1IEiEDcn9ITj431ryzHqk5pWeDWIofFTz/view?usp=drivesdk

 

This doesn't work for me. Denied access.

 

Find a free picture hosting site such as imgur. Store your pictures there and when needed copy the information and bring here to post them.

[Awkyeow]

I have done valve adjustments in the past. It is still making the same noise. What am I missing?

[datzenmike]

I haven't heard it but is it louder under load? and quieter off the throttle?

[None_zero]

Is it possible it isn't from the timing chain at all bur rather from the oil pump? My 720 has developed a ticking sound that was alarmingly loud and I believe it's coming from the oil pump. Some folks may remeber that Mike and I been in the trenches trying to fix that pump since i randomly took it off one day to "see what that looks like on the inside" not knowing what a royal pain in the foot it is to replace properly. But this noise started after pulling the carb to seat new gaskets under it. Haven't touched the pump. Oil Def needs a change I'm about to go get a filter Soni can do the swap to Rotella 15w 40

[datzenmike]

10w30 is also available in T4.

[DwayneOxford]

1 hour ago, None_zero said:

Is it possible it isn't from the timing chain at all bur rather from the oil pump? My 720 has developed a ticking sound that was alarmingly loud and I believe it's coming from the oil pump. Some folks may remeber that Mike and I been in the trenches trying to fix that pump since i randomly took it off one day to "see what that looks like on the inside" not knowing what a royal pain in the foot it is to replace properly. But this noise started after pulling the carb to seat new gaskets under it. Haven't touched the pump. Oil Def needs a change I'm about to go get a filter Soni can do the swap to Rotella 15w 40

I use a short piece of garden hose to pinpoint noises.

[None_zero]

16 hours ago, datzenmike said:

10w30 is also available in T4.

Thanks I actually got the 10w 30 because it was all they had so I'll use that and t him finish her off with the 15w 40 giving me a 10.45 w 32 oil (precisely) no I'm kidding about the new classification of oil. @DwayneOxfordyes sir I used a length of pvc to locate mine 

[None_zero]

18 hours ago, datzenmike said:

I haven't heard it but is it louder under load? and quieter off the throttle?

Oh and this is probably the big Indicator that we are having different issues. Mine is quieter under load in fact anything above idle makes it go silent 

[None_zero]

16 hours ago, datzenmike said:

10w30 is also available in T4.

Love how he mentions this after I've had that 15w 40 on the shelf in my shop for what four months - 6 maybe waiting for the right time to swap it lololol

[Awkyeow]

My noises are more at idle and right after you take your foot off the gas.

My clutch fan is too loud to hear if it is there when I rev the engine. I have not had time to change it. I have a new one though. I do not believe the noise is there when under load. Just at idle.