Hey everyone,

The engine in my brother's 86 TA (305, manual) makes a ticking noise, but only under load and at low RPM, from around 1000-2000.

Any idea as to what it could be?

 

Ticking is usually lifters or valve lash, if the oil isn't known to have been changed sometime in the last 4-5k miles, try that, and maybe some kind of oil treatment product. If it still does it you will most likely have to live with it or tear the top end apart, but without getting someone that knows what they are doing to actually listen to it in person, I would not tear it apart.