Did you check the EGR?EGR helps prevent detonation and preignition under load and if it’s not functioning properly it MIGHT cause the engine to make noise.
idling ANYTHING for an hour is Not Ideal.
Quote from: anti-squirrel on November 30, 2022, 11:05:24 AM idling ANYTHING for an hour is Not Ideal. I had a Guy tell me that once after I had done a complete rebuild on his 1973 Triumph Trident!
The X-75? Those had a limited production run of 1200!BSA/Triumph went Bankrupt the next year.I've only ever seen the Prototype in Pickerington, Ohio.On the Nissan? Autozone can plug into the ODB port and see if any trouble codes show and that's free.I worked with my Dad for years in his Garage but when things went to computers? We couldn't afford the equipment so only worked on older stuff.Now days? I have software and hardware and can completely hack my vehicles!
Check the exhaust manifold to the pipe bolts. They could be loose or the donut could be missing.
Not for nothing but I might check universal joints, clutch and throw out bearing. All of these can make pinging and whining noises.
A D-21 hardbody? Awesome darn trucks made during an area of great compact trucks. If you do a compression test, try a leakdown test. Compression gives good info, too, but I never do one without the other. I'd be inclined to check actual oil pressure, too. And it never hurts to look at slop/runout on the brake rotors up front if you have it up on stands (may as well check the entire undercarriage)Those hardbody engines are robust... but idling ANYTHING for an hour is Not Ideal.