Datsun Roadster Forum-311s.org

If Greg is right there would have to be a lot of chain slack. Is there? Is the the right (non-tensioner side) tight or very slack?

If you still have not found something obvious, I would start inspecting rocker clearance. With a given cam lobe pointing sraight
up, there should be no more than .010" gap between cam and rocker. If you find one with way more, something is amiss..

Frequency of the sound leads me to believe it is the chain running against something. The valve and rocker noises ive heard were always more clacking. Inspection of the chain guides may show some missing rubber and wear marks there, if so it will make similar sound. Just don't see bright wear marks in any of those pics. Check the chain slop and replace it and the related components as needed.

Thank you all again for the help. I haven't been able to get back to inspecting yet and can't until after Saturday. Too many home things going on.
Great to get some direction and tips though. I will follow up on the suggestions and report back. Many thanks.

I would put the VC back on and leave the front cover off. Start it and see if the tensioner foot is pulsating. It could be an oil starvation to the tensioner. It is too fast to be a single rocker / cylinder issue. If you have ever rotated the cam without the chain on the gears you will find that there 8 ramp up / down events caused by the valve springs which causes the cam to "Jerk" a loose chain.

Well, finally got to run some tests. I've found that the noise comes from the upper tensioner. Seems the seal or rubber on the rear of the tensioner somehow broke down, so the ticking was coming from the tensioner hitting metal as it retracted. Anyone seen this before and would this happen because of another issue or just the seal coming loose?

The pics are of the damaged seal and a top view of the tensioner from the passenger side. The screwdriver is pointing where the rubber failed.
The tensioner still pulsates when the chains move.

I don't see any other damage.

There are two washers (or shims) on the shaft of the tensioner. I see that Datsunparts.com sells shims/rubber for this. Is this an appropriate fix? Or do I need to replace the entire tensioner.

The chain and gears still look good.

thank you everyone for your help and suggestions.

-leo

You can get a new foot/plunger for the tensioner.
As Greg has mentioned, there is a small hole in the block that feeds oil to the back of the tensioner plunger to hole the plunger against the chain and keep tension on it.
It's not unusual for someone to make a gasket and not cut that small hole which plugs the oil feed and does not pressureize the tensioner plunger.
So, remove the tensioner. Get a new plunger and gasket. Clean it well, run a small wire into the oil feed to make sure it open. Discard the "bent tab" retainer and reinstall with a little locktite on the bolts.
If it were my car, I'd replace that chain if its' been running metal to metal.
Dan

hmmm, I am not familiar with a seal on the tensioner shaft. The pulsating may have something to do with variable oil pressure...perhaps a oil pump problem or some type of partial blockage in oil flow to the rear of the tensioner. Suggest you pull the tensioner off and make sure the oil flow hole is clear and paper gasket is good.

Shims are only needed if your chain has stretched. It moves the foot out to contact chain sooner before oil pressure come to full pressure. The "gasket" you found damaged may have been a rubber shim from a previous owner?

Seems like grey dog beat me to the post. Nonetheless I totally agree with him!

Looks like someone put a rubber shim or o-ring on the tensioner plunger shaft in order to keep the tension tighter under start up conditions. Very common, as under those conditions the chain will be loose until oil pressure builds. You can replace with another or run without it. Most recommend using a shim.

Unless the wearing face of the tensioner is damaged, you don't even need a new foot. That rubber washer is simply a cushion, Not a seal-- all it does is cushion the impact of the rear face of the tensioner body. A fat o-ring or a nylon washer will work perfectly. Note you only need about 1/16" of free tensioner travel - much more will create potential issues (sounds like you have way too much).

There is a check valve in the tensioner body. With oil in the tensioner the valve keeps the oil from being pushed back in the oil galley and keeps the foot from pulsating when the oil flow is low. You might want to make sure that valve is working correctly and I would also recommend you shim the foot to minimize chain slap when starting.

Just to be sure, do check the operation of the tensioner. The gasket is not hard to reproduce if you see a picture of one and are careful to not obstruct the oil feed hole. I make mine out of very thin gasket paper, no sealer. While you've got it open, why don't you take a nice, clear close up picture of the cam gear, with special emphasis on the teeth that are not engaged in the chain (bottom). That may give you some idea as to the state of wear of your gears in general (guessing here). If they look like they are undercut (like a little Christmas tree) then the gear is worn. Make sure the tensioner isn't chewed up. Do shim it. Hope all is Well!

+1 Spyder.

Pics of the engine... she looks kinda dry... where's the oil? Is it oiling well?

Was checking for valve spring coil bind today, so I was spinning the engine around by hand. I noticed just how much the unpressurized tensioner moves and what it allows the chain and subsequently the cam timing to do, which is jump all around! My tensioner was not shimmed enough to stop this, so I got some more nylon washers. Good now, just a bit of movement.

How are things coming along?