As some of you know I aim to build in accordance with the 750mc regs. One of the stipulations is valve size. Here is what they say "Maximum valve sizes are Inlet 1.5”, Exhaust 1.24"

So based on that I checked out the valve sizes according to Haynes for my std 1300 head.
Exhaust - 1.234" to 1.244"
Inlet - 1.497" to 1.507"
..and as you can see, the std head is right up to the regulation limits.

Mention is made of the 1100 lc/hc/2v, 1600 but not a 1300GT or 1300 2v or any other variant.


I know the GT has a different inlet manifold / carb and different cam, but people seem to want to get holf of the GT heads.

So my question is, why do people go for the GT heads?