Rob makes a good point about the effects of larger wheels and tyres. One well regarded improvement is replacing the heavy steel flywheel with a lightweight aluminum one (or a machined and lighter one).
There is a down loadable spreadsheet at
elan-f15/updated-spreadsheets-t18445.html that has the capability to estimate acceleration times and allows the user to change wheel weights, tyre weights, flywheel weights, etc and see the effect on acceleration times. There are also other tables for the curious.
The tyre manufacturers website will often have technical information on each of their tyres, which usually includes weight. So for any tyre in which you are interested, you can see the projected weight.
Also to be considered is the effect of tyre size, especially as they affect engine RPM on the road. Some members run tyres as small as 175/50-13. More commonly used is 185/60-13. Both of these are substantially smaller than the standard 155/165-13 tyres used as stock.
There is also another down loadable spreadsheet at
post82912.html (20080411zGearRatios.xls down at the bottom). One sheet is TiresS or tyres sorted by rev/mile. If you key in an existing or prospective tyre size in the Gearbox sheet, the TiresS sheet will give you the sizes sorted, with an indication as to which sizes are closest (or how far apart they are)
Starting from a relatively standard 155-13 tyre (912 rev/mile), possible choices are 185/60-14 (915 rev/mile), and 185/55-15 (904 rev/mile). If you run 165-13 tyres (887 rev/mile), close choices might be 185/70-13 (893 rev/mile), 175/70-14 (880 rev/mile), 185/65-14 (884 rev/mile), 175/60-15 (893 rev/mile), or 195/55-15 (893 rev/mile).
So, do the analysis and come up with an acceptable to you choice.
Cheers,
David
1968 36/7988