Dialing in cams can be tricky and take quite a bit of dyno time. Espeically on single vanos motors where we cannot play with cam timing independently in software like on the newer DVANOS cars. Cam movement/position must be adjusted manually, which means pulling the valve cover each time.
Usually, on the dyno, when doing this with an M50 based motor, I will *loosely* install the valve cover. (not all of the grommets, and none of the ones in the middle.) I also have the etorx socket for the 4 bolts on the exhaust cam shortened and welded to a bar to use as a wrench so that I can loosen/tighten the 4 bolts on the exhaust cam without removing the caps or moving the expansion tank or radiator. This allows me to quickly remove the valve cover, move the cam, and reinstall the valve cover quickly. Usually I am primarily concerned with the intake cam position, so I can forego using the TDC pin in the flywheel (just reference the front timing mark to make sure nothing moved) and use the cam block on the exhaust cam to find “home” each time.
Its usually about 10-15 minutes between dyno pulls when I am adjusting the cams this way. I have printed cam blocks that are degreed and will run once at each extreme (up to +/-10 deg depending on the cams, motor, if I had clayed on assembly to verify limits, etc) and narrow down from there. without the degreed cam blocks, you can use standard blocks and feeler gauges at the flat surface on the back of the head to calculate degree. To sanity check that, you can use an angle finder / digital level.
The valve cover will probably leak a little on each removal, but will also leak with not all of the grommets installed. Removing and reinstalling the valve cover gasket so many times will also mean that the last install of it will probably be short lived. When the tuning of the cams is done, I’d put a fresh valve cover gasket on it then.
If you are looking for more peak power, and it looks like things will respond well to retarding the cam more, that does a few things. Retarding the intake cam will move the power to the right, and if sufficiently retarded, will allow for more vanos travel as well. Keep in mind that the more you retard it, and just letting vanos advance more as a result, just helps not lose as much in the RPM’s where vanos is advanced. It won’t gain anything there. If you reach a point where retarding the intake cam more will either a) lose more down low than it will ever make up for up top or b) move the target peak to an RPM that isn’t feasible. at that point, advancing it again is better.
Tune wise, we can set one with vanos advanced to redline (though be careful with this and any possible valve float, as if it was close, this can result in valve contact. might be worth lifting before redline on the first run.) we can then set one to not advance the vanos at all. We can do this with timing flat in both cases, so we see purely mechanical results of the change.
Another approach is to tune with vanos retarded for all of the cam timing and base tuning/adjustments. From there, when power in the target range is optimized, add vanos back into the mix. You have options there too. See if you can get full vanos advance and let it help with the low RPM, but knowing it might have to be turned off early for safety, and result in a dip in the midrange. Option 2 is to pick that second peak, and probably put it as close as possible to the most used RPM range. (i.e. it’ll do less in the midrange, but you can leave it on longer.)
If we know the target RPM range used (RPM histogram from the usual tracks in normal conditions) we can help make the most total power in the most used RPM range. That is what makes the car the fastest, even if the peak number isn’t the highest.
VANOS is a tool. It is used to advance the intake cam. When it advances is controlled by the ECU. How far it advances is mechanically defined by either a shim in the VANOS unit, or by other mechanical means. Each cam position (retarded and advanced) will have its own torque peak RPM. The distance between those RPM’s will be a function of the total cam advance angle possible. Thus, it is possible to have two peaks only a few hundred RPM apart, or a couple thousand RPM apart.