I want to put V3/V4 sti heads on my 1998 uk classic but what are the differences between the the versions if any??

Thanks,
Joe

 

The cams are of a wilder profile on the version 3 compared to the version 4.

Banny

 

I've never understood what "wild cams" actually are??

 

I beleive the inlet cams' profile are shaped so that the inlet valves are open for longer. This has the effect of more air going in on the induction stroke, thus typically making more power further up the rev range. This is referred to as 'duration' as the cams allow the valves to remain open for more duration of the cams' rotation. As a result the 'wildness' of the cams' profile is expressed in degrees of rotational duration.

The reason why they are "wild" is that they typically come "on-cam" at, and above, a specific rpm point and then really make a mad rush for the redline (not to be confused with VVT mechanisms though - although the idea is similar). Unlike VVT systems, because the cam profile is fixed, then 'wild' cams normally suffer from lumpy, uneven, bad low speed running. Really wild cams i.e. those intended for racing cars (and not fast road use) are designed to thrive on race-circuit high revs and, as a result, are NOT suitable for road car applications.

Blimey, this brings back memories of the 80's Mk.I and II RS1600/1800/2000/Mexico Escort "era" with their slammed suspensions, bright red Peco big bores, Kent and Pinto crossflow engines, twin-choke Weber DCOEs and, of course, fast road or racing Piper cams! Happy days.