Sorry if this is an old query but I can't find a consistent answer to this question. Is there a difference in valve size between 1600 GT heads and standard heads. I've read all sorts of conflicting information. Some say GT valves are bigger some say they're the same size. Anyone know what the sizes are?

Cannot tell you sizes but the GT head definitely had larger valves than a standard 1600 escort 30 years ago, also had a banana exhaust manifold and twin choke weber.

Turbosports forum will tell you all you need to know

According to the info I have, the 1600 and GT have the same size 1.5" inlets 1.25" exhaust.
Same size exhaust valves as the 1300.

Have a look at Burtonpower, sure they list valve sizes