I am wondering if there is a reason, other than being able to tell them apart, why the exhaust and the intake valve guides have different profiles. On the original Lister the exhaust is threaded and the intake is press fit. The Indian made ones have both be press fit.
I am asking this because on on a twin, the two heads are identical (same part numbers), and the location of the guides is switched from one head to the other, so the intake ports are adjacent to one another. Therefore the holes where the guides fit are identical and the valve seats are also identical. I thought the purpose of the valve guide is to keep the valve centered. if that's the case, then their profile could be the same unless the forces on the exhaust side make it such that it needs a longer guide...
Don't know if this makes any sense, and perhaps it is obvious...I figured if there is a good answer people on this forum would know it.
Cheers
Moe
