R16 Engine knock

[Greaser2]

I’ve just noticed an engine knock in my R16. I noticed it while adjusting the carbs, seems to be prominently in the 1500-2200 rpm range. Don’t seem to hear at >2500 but maybe it’s just too loud. I do hear a knock at idle as well. It’s not in rhythm with the rpm’s (seems much slower), 1-3 knock per second, mostly 2-3 knocks per second at 2000rpm. At idle, 1 knock per 1-3 seconds if it knocks. It doesn't knock 100% of the time. Don’t seem to hear it on a hard acceleration either but perhaps the sound is drowned out. I've checked the lash, did some minor tightening but no change. Working on mocking up a oil pressure gauge next. Thoughts on the issue? Sticking valve, piston slap, timing chain (See below).


Background, don’t have much experience with this engine, it came not installed with the car, supposedly it had been rebuilt couple of years prior but never reinstalled. I opened it and it looked very clean so suspected it had been rebuilt. I installed and did a little driving 5-20 miles and didn't detect the knock.
Prior to second install, I did replace the timing gears and chain as they were in bad shape and reinstalled at the rebuild so that was a concern. Thinking the rebuild was lazy. Could this cause a knock?

[Gregs672000]

Very difficult to tell... I've had to chase one on a U20. Knock or tap? What's the frequency sound... clonk clonk or tap tap? Do the plugs show any difference? Does the engine act differently? Search for anything exterior to the engine... alternator, water pump, vibrations. Try listening with an engine stethoscope you can get at an auto parts store (be careful, it can be loud if you bang it on metal). I'm not very experienced with the push rod valve train and others can chime in here. Mine turned out to be a broken wrist/piston pin and I was very lucky to not lose the motor. It would not tap at idle, started at just under 2000rpms and would seem to lessen at higher rpms but my induction is loud and my hearing bad so I'm not sure. The tell tail was it starting at just below 2000rpms, and it was a consistent sound... tap tap tap tap. There are a few YouTube videos out there. The pin was allowing the piston to move side to side in the bore, taping on the cylinder walls. Another possibility is a lose valve seat but engines typically don't last long when that happens and it might show up on a spark plug. You could get a bore scope to try and look. Does it change with temp? Compression test, though mine didn't show any difference.

[Bwk2000]

With your description “It’s not in rhythm with the rpm’s” and a variable ‘knocking’ rate at a steady rpm, that would lead me straight to the timing chain first. Piston slap, connecting rods, crank sleeves, bearings, etc all will be very noticeable and correlated to engine rpm. Spark knock is another thing (might not hear it that well if the engine is really loud) but I’m sure you’ve already checked that and eliminated it as the problem … same with having bad fuel or running it way too lean (a simple spark plug inspection will ‘tell-the-tale’ for these potential issues). So, as Greg suggested, get, or simply fashion your own engine stethoscope and localize the sound at idle (both when cold & fully warmed up). If it’s loudest at the timing chain cover, or even just at the front of the engine, you likely have your culprit.

[redroadster]

With it knocking ,pull the plug wire of that cyl if it mostly goes away it's a bad rod bearing or piston pin issue / crank journals etc.

[Greaser2]

I would say its between a knock and tap. Its not a loud/bad sounding knock but lower pitch then a tap and it is not a consistent repetitive knock and much slower then the rpms. I will try the stethoscope but it seems to be coming from low and middle of the engine, not a good area. Engine runs really well otherwise, no unusual shaking or other, the SUs are fresh rebuilds from Ztherapy. Set at 16degrees, lash is 0.017 hot. This is a 411SSS and have several of these so very familiar with how these should run.

Seems to get more consistent as the engine gets hot. No sounds at cold idle.

Will pull the plugs and try pulling the wires individually.

[Bwk2000]

If the noise does turn out to be lower/middle of the engine, might be a good time to check the oil pump itself.

[Greaser2]

After searching for awhile with a stethoscope and about to give up seems to be low in block, driver side, in the 1 or 2 cylinder area. Maybe the timing chain, otherwise the engine may need to come out. End play maybe.

[Greaser2]

Should the wind age washer float on the crank? Looks like it will get pinched in place when the pulley and bolt are tightened down. Otherwise everything looks fine here.

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[redroadster]

The cam gear is worn in a place, and the crank gear looks worn ,what I see
The engine stops usually in 1 spot or 2
Good time to replace all timing components...., yeah should pull the sp wire of when it constant knocks
If it's bearing clearances it will loose it then
OK , understand , I thought the cam G was worn some by the pic , might be a nut went down it

[Greaser2]

The gears and chain are brand new, maybe 5 miles on them.

[Bwk2000]

Is the backside of that oil slinger chewed up?

And since I can’t see the crank gears well, are they also SAE?

[david premo]

So the question is have you ever had the head off this specific engine. The reason being stock R-16 engines have domed pistons and they have been known to hit the head if the head has been cut too much. So what I used to do with 1600’s is set the head on the block without a head gasket and rotate the engine. If the head moved while sitting on the block, knew I would need to relieve the head or run a thicker head gasket. It might be that the piston is just kissing the head as it warms up.

The only other thing that comes to mind is a potential sticking wrist pin. It would be a good idea to take your time with this and find the problem before it’s a catastrophic failure.
Dave

[Greaser2]

Is the backside of that oil slinger chewed up?

And since I can’t see the crank gears well, are they also SAE?

The more I look I think the slinger is fine, I put the pulley back on and snugged it up and the slinger is tight and the marks are just from being pinched between crank gear and pulley.

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[Greaser2]

And the gear set was the Early/Late timing set from Datsun parts, you can see it’s set at early as this as a 3bolt SAE

[Greaser2]

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Engine is out and head is off. Didn’t see any signs of valve and piston interference.