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Datsun 521 Engine Noise

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So back for some more help. My engine is making this noise(link). I know about lifters, rod knock, piston slap, exhaust leak. I mainly work on rotarys and those either work or they dont🤣. Anyways, so i wanted someones opinion on what could be making noise. It sounds "metallic" truck runs and drives

Might also have a headmaster issue but that's another story.



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@Stoffregen Motorsports i will check the bolts on the manifold. Maybe after running, they got loose. The gasket is new so I hope it still seals

I'll have to look for info on how to adjust those bits, since rotarys don't have this stuff haha. This engine may be simple, but I still lack the experience.

Thanks for pointing me where to start

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Definitely louder on the exhaust side. Look at the flange gasket between manifold and down pipe.


It does have a shake. Perhaps pull each plug wire off one at a time and see if one has little effect on running. May be a 'dead' cylinder. This may go away when you set the valve lash.


As to the shake go through the procedure for setting the Weber idle mix.


Get rid of the little red filter and connect a hose from the valve cover to the white elbow fitting on the air filter. Less mess and fumes.

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Checked for leaks as much as I could.

No luck.

I unplugged the spark plug wires one at a time and each time it ran poorly.


It's looking like it's a valve adjustment issue. Will have to see. The headmaster needs replacing it has coolant dripping from between the block and the head.


Thanks for your input everybody

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Try a compression test and look for a low cylinder or two adjacent low cylinders.


Still sounds like exhaust squeezing out somewhere. I did have a headgasket blow out to the spark plug side but spit out water as well.



If exhaust it should be louder under load driving.

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If doing the head gasket I have to warn you that the timing chain tensioner MUST be secured before the cam sprocket is removed. Find out how before you attempt to change the head gasket.

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7 minutes ago, banzai510(hainz) said:

what is HeadMaster?


Remeber the L series has water passage holes in the head and if the intake exahaust gasket get loose it can leak making it look like a headgasket.


the 521 is a clean simple of the Lseries as not much emmissions in the way.


Headmaster is the popular girl at every event.

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Well this is sort of a project between me and my dad, and he decided to bring it to a shop, so we will see how that goes. The old guy seemed knowledgeable on the truck, and definitely has more experience than me. So I guess we'll see. If not I might be learning the hard way

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The correct way to adjust L series valves is with a skinny feeler gauge stuck in between the tip of the rocker arm and the valve tip. It has to be skinny because of the valve lash cap. If you don't have a skinny feeler gauge, you need to get one.


Cold, means cold. Not run for even a minute.

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I like setting clearance on a hot engine as that is the setting it runs and remains at. Cold setting assumes that the heat will expand everything properly but what is a cold setting? What if it's 40F in the fall or 85F in the summer?? That's a 45 degree difference in expansion.


Hot setting of the L20B is 0.010" and 0.012" for intake and exhaust...


As the rocker arm ratio is 1.5 to 1 any clearance adjustment at the cam means a 50% larger clearance at the valve tip. So a 0.010" intake setting is actually 0.015" at the tip. The 0.012 exhaust is really 0.018". No wonder there is noise!


To reverse engineer this, to get a hot clearance of 0.010" at the intake valve tip, the clearance at the cam should be what? 0.0066" (0.00666 X 1.5 = 0.0999")

For the 0.012" hot exhaust it would be 0.008"


Does this sound right?? Anyone see anything wrong with this approach? 0.006" at the cam for the intake and 0.008" at the cam for the exhaust.


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8 hours ago, thisismatt said:

I wasn't going to say anything as I don't have a strong opinion about it, but the FSM shows it at the cam


23 minutes ago, Slow Loris said:

Well if the manual says cam then presumably the Nissan engineers already did the math for us and we don’t need to. You’d think?


Agreed. I took a very close look at two of my FSMs and you can clearly see the feeler gauge is under the camshaft.



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