240 Bad camshaft torque?

hi! I have a lot of small problems with my 240, a lot of them done and rebuild 80% of car still driving it daily but never have problems with engine... But now something happened...

So, 2nd time since 2018 i gave my car to only specialist shop (volvo rwd cars only) and they found out there was bad valve clerance. they set up everything to good numbers. After that i made home (300km), i made engine flush and oil change (as always) - Liquy moly flush and 10W40 oil with MoS2, made 1400 km trip and i heard something while i was driving with 2-2,5k rpms. It was strange noise coiming from exhaust/engine side so i open hood and check. there is noothing on idle, nothing on low rpm but ther is weird knock on 2-2,5k rpms - it's realy related to inside engine movment. When i use throttle with my hand i feel thats something knocking inside engine....

Any ideas what can happened? I maintain my car all the time, i change oil every 10k km, almost all seals in engine are new (only headgasket and exhaust mainfold gasket are 31 yo and 398950km old), never have problems with it...

Can it be bad camshaft torque? Should i remove it and torque it with spec or just torque all bolts without removing it?
What it can be?

PS: this long drive was probably my slowest and calm drive since i ever own car (gas price, long distance, chilout roadtrip) so i don't think i do something bad with using car (i never reach more then 3,5k rpm while driving my Volvo)

Volvo 240 91' B230F+LPG M47

Check the oil pressure and also you can check the valve clearances and see if anything changed after the trip. A compression test will help get an idea of what's going on and if
further diagnosis is needed a leak down test will show what is
bad in each cylinder.

The last thing that was done to the car was adjusting valve lash. (not a surprise it the car has been running on LPG for a long time)
The lash will have been tight. The mechanic will have replaced the shims with thinner shims to get back to lash specifications.
maybe you can remove the valve cover and visually inspect the valve springs and the shims. (something could have gone wrong, maybe one shim has jumped out of it's bucket?)
You can also test if any cam bearing caps are lose.

If the running engine makes a strong ticking sound in the rhythm of engine revs then maybe also check the exhaust for leaks (between head and exhaust manifold and between manifold and pipe). A blown gasket in the exhaust system can produce ticking sounds that may sound like a mechanical problem.

dl242gt said:

Check the oil pressure and also you can check the valve clearances and see if anything changed after the trip. A compression test will help get an idea of what's going on and if
further diagnosis is needed a leak down test will show what is
bad in each cylinder.

Click to expand...

Oil pressure is on standard leve, i have even accesory oil pressure gauge.
I check clearence and everything is in spec, check camshaft for damage - there is nothing bad, everything in prefect condition.

Janspeed said:

The last thing that was done to the car was adjusting valve lash. (not a surprise it the car has been running on LPG for a long time)
The lash will have been tight. The mechanic will have replaced the shims with thinner shims to get back to lash specifications.
maybe you can remove the valve cover and visually inspect the valve springs and the shims. (something could have gone wrong, maybe one shim has jumped out of it's bucket?)
You can also test if any cam bearing caps are lose.

If the running engine makes a strong ticking sound in the rhythm of engine revs then maybe also check the exhaust for leaks (between head and exhaust manifold and between manifold and pipe). A blown gasket in the exhaust system can produce ticking sounds that may sound like a mechanical problem.

Click to expand...

Everything is good, in specs - i check all of thing i could. And yes. there is ticking and swirl sound but it's because old exhaust manifold gaskets (i know i should change it but they are stuck so head gasket will be best time to do it at once). Bearing caps are good, camshaft os good - that's probably something lower then camshaft...

With almoust 400k km on a motor, can it be piston slap ? is there any diffrence in sound cold / warm ?

MaTus_SVK said:

With almoust 400k km on a motor, can it be piston slap ? is there any diffrence in sound cold / warm ?

Click to expand...

It's not piston slap. That knock where ther all the time. Right now i rebuild motor, we will see what happened.

Is it possibly pinging? When I refreshed my engine I installed the timing belt slightly off, would start pinging under load at high RPM

B230's can get cam rattle, also the torque for the cam caps is only 7ft/lbs or 10n/m. Over torquing will cause a very tight bearing and I wouldn't be surprised if the cam bearing clearanced itself, the rear most cam bearing on my car is that way. A previous "Volvo specialty shop" rebuilt the head. That could have happened from an over heat or low oil though. The exhaust heat shield can also rattle and make a racket at certain frequencies. A 240 cabin isn't very isolated from the engine bay, if the heat shield is buzzing you'd probably hear it while driving. I wouldn't rebuild a redblock because there was funny noise that is undiagnosed while everything else checks out to be healthy.