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3rzfe tapping noise

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Hi all

i have just run in my new 3rzfe turbo engine in my hilux, mods to motor are main studs, spool rods, cp 10:1 pistons 1mm over, cometic HG, arp head studs stock cam, 100pound valve springs Ti retainers, link atom e85

im trying to get to the bottom of a tapping noise, i can mostly hear it at 100kmh crusing 2700rpm it increases in speed as rpm goes up, seems to get louder and quieter, checked valve clearances they were good, all bearing clearances and piston to bore clearances were checked and good when assembling. timing chain we tight everything thing is checking out good.

i read your write up on the exhaust cam toyota scissor gears today mine was assembled with the service screw in and removed there seems to be good scissor tension there.

the noise seems like its a valve train noise, could my scissor gear spring have lost its tension and or its not working well with such heavy valve springs?

or are the heavy valve springs slamming the valve shut hard to cause a tap also i have stainless steel exhaust valves would they be nosier?

or do forge piston sometime still rattle when warm?

chasing some ideas on what else i could check

Does it change under varying load? Does it change the cruise speed it occurs at, or rpm, when changing gear. Have you tried free rev'ing it around that rpm when stopped and the bonnet (hood) open to see if you can isolate it*. If a manual, does it change if light pressure is applied to the clutch*? Is it continuous, or come and go*? Are you using the original camshaft and the followers are in their original position?

* a few odd things I have found that took a little figuring out.

Heat shields that hit a resonant period at a specific rpm that made an audible sound but only at that rpm - found by holding the engine at the rpm and tracing the noise.

Less likely, had an engine with an external balance weight that 'just' caught the tin clutch cover shield (access plate) and applying the clutch just moved it enough for there to be noisier contact - I had thought it was a bad lifter, or several, and the noise was being transmitted through the linkage, but turned out not - just needed a slight tweak for clearance.

I don't think it applies here, but if it's variable I had a case where a follower (lifter) was unevenly worn and would get louder and quieter as it turned.

Valve springs, and the SS valves, are unlikely to be a factor as the spring's main duty is in holding the valvetrain in contact from the opening clearance ramp to the closing clearance ramp - there's no "slamming" unless in valve float/bounce.