Thread: One for the V8 Gurus

I am doing up a 3.5 V8 for my Disco.

I have been doing some research on cams. Seems the standard factory cam is pretty good anyway. Some people say a 3.9 cam works well in a 3.5. AFAIK the 3.9 has the specs as the 3.5 but has about 2 degrees more advance. Does that seem right? If that is the case I might just stick with the 3.5 cam and get an adjustable roller timing kit and set that with a bit of cam advance.

3.5 cam ETC 6099
3.9 cam ERR 5924

Does anyone have a factory cam spec chart?

Most of the aftermarket cams have more lift and seem to move the torque range higher in the rev range.

I have 8.13 to one pistons could I go to higher compression and still run on 91 RON?

Any comments?? Please

The 3.9 cam was advanced to bring the torque curve down, to recognise the extra capacity.
It is up to you whether you think the poor little 3.5 will benefit, but I think that you may be better off with a 3.5 cam.

With regard to the Compression Ratio, really the only elegant way of increasing it is High Compression pistons at 9.35:1 and you need 98 for that.
You can shave the heads by 10-20 thou but this causes some small problems with the fit of the inlet manifold and preload of the lifters. You will probably need to shim the rocker posts, which is not hard . The heads are supposed to be hard surfaced but I had no problems with 50 thou off and using composite gaskets for a net 15-20 thou off.

I have never fitted an aftermarket cam, and there have been many unhappy aftermarket cam buyers on this forum over the years.

If you go for an aftermarket cam go for the towing cam which is usually the mildest. Many "specialists" and one in SA that works on TR7-8s seems to think that "mid range " cams are OK , But I recall a buyer was on here complaining of no torque to climb the Adelade Hills. OK in a TR7-8 perhaps but not in a 2+ tonne RRC.
Regards Philip A