SABLT194

These have been out for a while now and I've read a few old posts but no real feedback in them. Has anyone tried the XFI grinds yet? Any Dyno results? I've heard mixed reviews on the beehive springs. Anyone running those to 6800 successfully? Thanks

SStrokerAce

The XFI lobes are a new series from comp that are higher lift than the XE lobes and about as aggressive, but they have more development time from what Comp has learned on the spintron.

As for the Beehive springs, yes I've used them up to the 6800-7000rpm range and they work awesome if you set them up with the right cam and right valvetrain parts.

The combination of XFI lobes and Beehives might not be the most RPM friendly, even if you look at the big Comp XFI cams they don't list them turning to much over 6200rpm.

Bret

Type_O_Negative_1320

While we're on the subject of XFI grinds...

I have a cam sitting on my shelf that I had cut a while back...it's from Comp and used the XE lobes. Specs:

Advertised duration: 293/299
Duration @ 0.050": 242/248
Lift with 1.6 rockers: 0.576"/0.599"
LSA: 114
IC: 110

I was looking through the new comp catalog and found an XFI grind that nearly matches the cam I had cut (??? will be replaced with actual numbers when I can find them...don't have the catalog in front of me):

Advertised duration: ???/??? (less intake and exhaust than my XE grind)
Duration @ 0.050": 242/248
Lift with 1.6 rockers: ???"/???" (more intake, less exhaust than my XE grind)
LSA: 113
IC: 109

How different is the XFI grind compared to the XE grind that I have now? When I had mine cut, the guy at Comp told me "that won't work, it's too big for an LT1". I ordered it anyways and then they came out with this XFI grind with nearly the same specs half a year later. It just seemed kind of strange to me, especially after they told me mine wouldn't work.

SStrokerAce

The basic difference between the XFI lobes and a XE lobe is the actual aggressiveness of the lobe. The XE lobes are more aggressive than the XFI lobes but the XFI lobes have more lift and more area per amount of duration. They also split up the intake and exhaust lobes due mostly to needs of each side of the motor and the valve mass being vastly lighter on the exhaust side of the motor. When it's that much ligher you can make things more aggressive without too much work. The XFI lobes were also designed to work with beehive springs and Pro Mag rockers with the primary rocker ratio being a 1.6:1 ratio. It's basically a more modern version of the XE lobes.

If you notice the 242/248 cam the spec is listed for a 2200-6200rpm range... that's pretty low for a cam with that much duration. The base setup that they have for these cams and lobes is not super good for over 6000rpm operation.

Bret