Solid Roller Cam ??

[Barry_R]

I have not signed in on the whole beehive thing yet. In agreement with Keith on a lot of this stuff. Between the two of us I bet we've installed a thousand cams or more.

Reducing the mass of the retainer is nice - but no way is it enough to compensate for a 30% reduction in spring rate. They were probably oversprung in the first place and playing with fire afterward. Might be lofting the valve over the top of the lobe to gain some "cheater lift" knowing that durability was not going to be a factor in testing.

You CANNOT directly compare the opening and closing specifications of roller and non-roller, solid or hydraulic cams at any point unless you do all the measurement at the valve. Making assumptions about the entire lobe profile based on what happens at a small and arbitrary lift point - such as .050 - is also way overly simplistic. These days a sophisticated lobe is entirely non-linear in design. An awful lot happens at .100, .200, .300, .400 etc and none of it is similar from lobe to lobe.

Cams are best expressed as lift curves plotted at the valve over the entire range of action. You never see this data provided by any cam suppliers. You can have two cams with similar duration measurements at .006 (SAE), ..050 lift, and peak lift that will be completely different in terms of lobe area if you measure them this way.

Lash is a very modest tuning tool. You need to keep the valves closed when cold. And they need to remain in control over the full lift curve. Once the lobe designer has decided upon a lash ramp and built that into the lobe profile you should not move too far away from it. A bit tighter rarely seems to hurt things, but looser can play havoc if the lifter tags the lobe beyond the ramp.

As much as I hate to say it, there is no "keyboard" way to select the perfect cam. I wish there was. Because the perfect cam does not exist. All we can do is try one we know will meet the individual customer's expectations and run with it based on EXPERIENCE. Some guys want more of a rumpity idle, the next guy will want more top end, the next guy will want smoother driving. I've had the same cam described as too smooth and too wild within a week in comparable builds.

With the Engine Masters Challenge FE entries I have installed lots of cams into the same engine to see what happens. It rarely follows common predictions - we've had great results with way too big a cam installed insanely advanced. You need to TRY things. The engine cannot read.