Thanks for the replies.
I've managed to find my ancient set of feeler gauges, and can just get a 2 thou gauge between the teeth, 3 thou gauge long gone, but a 4 thou won't go in, so I will leave it at that!
Interesting conundrum about the heat expansion though.

Location: Bonnie Galloway

Aluminium expands about 13 microinches per degree fahrenheit, iron about half that. The cam and crank centres are about 3" apart and assuming it all runs at about 150 degrees F then the gap will widen about 0.003".
All figures approximate. Say between 2 & 4 thou.
(6.5 x 3 x 150) / 1000000 = 0.0029

Location: Melrose, Scottish Borders

Thanks for that Jim. It's good to know that the clearance will open rather than close as the car warms up.
I've never seen this rather important point mentioned on here before!

I've closed the bottom end up this afternoon, so it's **** or bust now!

Location: Bonnie Galloway

When I first playing with 7's I made the mistake of meshing a pair of gears too tightly, they started to break up on the M3 heading down to my first Beaulieu!

Location: Auckland NZ

On the same subject. Does anyone do new timing gears at the moment? At one time steel ones were available, are they still?

Stuart.

Dave Dye made a set of mag ones for me a couple of years ago. Andy Bird advertises, but he sat on my old ones for a year and then went off the radar completely.

Location: Somerset

Thank you, Dave is doing my supercharger drive at the moment, I will ask him.