There are two ways that the cam grinder can provide more lift. The first is to grind a new profile on the old lobe. The second is to build up the cam with weld, and then grind the new profile on that.
The first, is the one preferred by the grinder, as it is easier for them. They just chuck up the cam in the grinder, select the profile, ring the bell when finished.
When the cam is done this way, the cam profile is smaller, so there is more tappet clearance. So you just have to adjust the tappets to take the clearance up. But we have hydraulic lifters, that can only adjust a small amount of extra clearance, probably less than 1mm. Larger lifts give larger clearance, so shims have to be fitted under the lifters. Not easy.
The second way is to build up the cam with weld and grind the new profile, on it. This way the base circle is the same diameter, so the clearance remains the same. The lifters stay at the same position, and no shims are required. The pointed end of the cam, (the nose,) is now taller, so we have to make sure that it will rotate, without hitting the head casting around the lifter well, if so , the metal has to be removed to clear.
As the exhaust cam has 8mm lift, it stands to reason that the inlet can use the same lift, with out having any problems, of hitting the casting, or binding the springs. 9mm may be possibly. This is the most likely way for us to do it.
The 2.2 lt engines heads are completely different to our heads. Our heads are more like the WRX, twin cams over bucket hydraulic lifters, working directly on the valves. So it follows that what has been done, with camshafts on the Rex can probably be done on the SVX. I am not suggesting that we follow the same timing, as they have different objectives, but the lift problem would be the same. It would be good to research what they have had to do, to get the lifts.
Harvey.
