[DavidNJ]

Old designs. First, the short designs he tested are smaller than anyone would be using here. They are even smaller than stock, emissions-legal LS7.

Using hydraulic cams, and using numbers for .006/.050/.200, the Xtreme Energy XFI lobes (Vizard used regular Xtreme Energy, which are not current) are:

Short
Flat: 252/208/121/.298
Rolller: 252/202/128/.344

You would need a 260 in the flat tappets to equal the 252 roller at .200

Medium
Flat: 268/224/138/.325
Roller: 268/218/143/.356

equivalent to the a 274 flat. Also note that is .325 vs .356 lobe lift.

Long
Flat: 292/248/162/.365
Roller: 292/242/165/.365

Both are .365 lift. In this case, they are nearly identical.

Looking at solids I'll use the Tight Lash Solids, since the Xtreme Energy and Magnum solids where developed by Noah on the Ark. Using Xtreme Energy vs Xtreme Energy would not have been close. We used the Tight Lash on street stock oval cars in the early 90's with stamped Chevy rockers (required by the rules)

Medium
Flat: 268/238/147/.335
Roller: 268/230/153/.368

A two size advantage, equal to a 276 flat

Long
Flat: 304/274/181/.3934
Roller: 304/266/187/.398

Advantage roller, but not by that much.

It is harder to compare the latest race grinds. They have about 27 deg major intensity on both solid flat and roller. However, the flats are all big ratio rocker designs and the rollers aren't.

In the solid configurations, much stiffer springs are possible with the rollers.

So, it would seem that Vizard's analysis may be faulty. What is needed is a way to normalize the selection rather than pick from one vendor's selection of similarly named lobes.