[Cliff R]

I would like to point out once again, that it is NOT my objective here to bad mouth a particular brand of parts. I've been following the flat XE hydraulic lobes and the results of them for many years. I even tried one quite some time ago in a 400 engine using well prepared #16 heads. I chose the XE268 cam, and was somewhat disappointed in the results. At that time, I had no idea why the power just quit around 4800rpm's. The cam idled quite well for the .050" numbers and "tight" LSA, and made decent mid-range power. The power did however, end sharply at apprx 4800rpm's. The very similiar Crower 60916 and 60243 cams we had been using pulled well past 5000rpm's in nearly identical engines.

I started following the dyno and track results with the XE cams, and noticed that with few exceptions they didn't pull well past apprx 5000rpm's, even the larger varieties.

I just sort of sat on the information for quite a while, then got some DIRECT information from another engine builder, a cam design expert, and a dyno operator who does a LOT of high performance engines.

The other engine builder built an engine using the XE flat hydraulic lobes, and it would NOT make power past apprx 5000rpms. The dyno shop he used made him aware of the fact that he sees LOTS of very similiar results with these cams. They labeled it specifically "lifter crash". I contacted a cam designer, who told me specifically that the seating velocity is simply too fast, and can and will cause troubles at high rpm's.

We continue to see dyno charts posted from folks who show us very simliar results, few make good power in the high rpms with these cams, and quite a few of their engines show sharp drops in power up around 4900-5000rpm's.

Of course there are a few exceptions to this, as I mentioned in a previous thread, so it's not 100 percent for all applications. In any case, the percentage is high enough, that we avoid these camshafts and do not recomend them.

I will also say, that for years I blamed the poor results I was seeing on the short seat timing events, or advertised seat to seat duration. I was wrong, the problems are more specifically related to instability in the valvetrain/valve bounce/lifter crash (or whatever you choose to call it), rather that the basic design of the lobes (modern/fast ramp).

I felt compelled to release the information above, although I knew the first time I did so it was NOT going to be very well recieved. We're just seeing enough problems associated with these parts that someone has to point them out. Now go ahead and shoot the messenger, if you feel the need?.......Cliff