Background is that when I rebuilt the 110's engine (3.9V8, 9.35:1, hotwire injection) last year I ended up fitting a genuine parts 4.2 litre camshaft in the engine - I got it cheap and thought it worth a try.
Anyhow, having driven the 110 around for a while now, including to Italy and back earlier in the year, it seems to be lacking power from around
2,000rpm upwards - trying to keep 70mph on the flat in 5th (LT85 & 1.222:1 LT230, 3.54:1 diff and 265/75r16s) sees the vacuum gauge drop down to around 2" Hg and fuel consumption soar - you can tell the engine is really working hard. I don't think this can right - the 110 is heavy and unaerodynamic, but a 3.9 should be able to cope better than that (or am I being nieve...). Low-end is fine - she'll pull away happily in 2nd from idle and nips around town no problem.I recently found the numbers for the 3.9 and 4.2 cams and it seems that the 4.2 cam has quite a bit shorter duration than the 3.9 cam - 285deg. for the 3.9, 272deg. for the 4.2. My understanding is that longer duration means more top-end power, shorter duration more low-end torque, which would tie-in with my feeling that the engine is lacking top (mid-) power. The shorter duration means the 4.2 cam also opens later and closes earlier, with peak being slightly later on the inlet and slightly earlier on the exhaust.
So, if I'm going to change the cam, what's the best option, bearing in mind the 110 is quite heavy and I'm aiming for (relative!) economy at cruising speeds rather than performance? I'm leaning to the standard
3.9i cam, but is there a better alternative?Cheers,
AndyC.