Please Help - muffler or head?

hello all, my 73 standard beetle with a 1300tp is making some chronic noise when driving.

the noise is similar to a normal running engine only with a louder pinging ( its like a louder version of the sound of the tappets). the sound appears from start up and is consistent as the engine warms. it is only really badly noticable when it revs above 2500rpm, anything under sounds like normal, also sounds normal at idol. it has backfired only once in a week when going down a hill. initially i assumed it was the muffler, so i had a look and found a few black carbon spots where the muffler joins the heater boxes. i have replaced the brackets where the muffler joins the heater box aswell as the gasket where the heater box joins the head and used a muffler cement seal paste on both. no joy there unfortunatly. have covered the ends of the pee shooters and there is no evident noise, the baffles inside the shooters are still good as they are only 6 months old. have checked the muffler for holes and leaks but there appear to be none. all nuts appear tight as they should be. is the muffler shot? or is it the head? i am up the creek! please help, any advice as to what it is exactly and how to fix it will be greatly appreciated, if further info is required, will do my best to provide

nick
0422 721 253

do a compression test or ask a mech to that will tell you if one of the heads is cactus

Yes,
an old VW Mechanic can tell You if there is something wrong..
just by listening to the engine.......

Lee

thats awesome, never thought of that, if the compressions good, then chances are it'll be a muffler leak somewhere?

thanks again!
nick

Not sure if it's any help, but I went through a similar thing with my kombi recently. (type 4 motor)
A leaking exhaust gives out more of a "chuffing" sound and will cause back firing on an off throttle, and sounds like you've tried to make sure it's sealed aleady.
My leaking head emitted more of a squeak (my first thought was a slipping belt), which was noticable under load, and at any revs. The unfortunate thing is on a compression test it was only a few of psi down, which can happen in any normal motor anyway. I only found out it was the head from a knowledgable mechanic.
Good luck!!
Richard
🙁

Loose head nuts/pulled stud................probably on number 3 and 4.

remove rocker cover and rockers and check with a quality torque wrench.