Dyno guru Richard Holdener recently ran a cam comparison dyno tests on a 351W-based 408 cid stroker engine. The motor was built by Coast High Performance to the following specs:
- 10.0:1 Compression
- AFR 205 cylinder heads
- Edelbrock Super Victor intake manifold
- Barry Grant 850cfm carburetor
- CSI Electric Water Pump
- MSD distributor and 6AL ignition
- Hooker Super Comp headers (1 3/4" primaries)
The engine was originally put together with a
Comp Cams Xtreme Energy retrofit hydraulic roller, spec'd at 230/236 degrees duration and .545"/.565" lift on a 112 degree lobe separation. This is actually based on the very popluar catalog XE274H grind expect with more lift to help fill out the big cid and take advantage of the AFR 205 heads.
With the Xtreme Energy cam the motor baselined at 531 horsepower and 505 ft-lbs of torque, measured at the crank. Pretty stout considering torque is above 425 ft-lbs from 3000 on.
The purpose of the dyno test was to see if Comp's new XFI ("Xtreme Fuel Injection") STroker camshaft could better the numbers. The XFI Stroker cams are unique in that they are designed around the fact that stroker engines have faster piston velocity then the stock displacement engines they are bred from. As a result the longer stroke and fast moving piston draw the intake charge well past bottom-dead center of the stroke. The XFI cam intake and exhaust opening and closing points are therefore tailored to take advantage of the increased filling at the end of the intake stroke.
Comp's catalog recommends the cam for fuel-injected 347cid, or larger, SBF engines with at least 9.5:1 compression and of course upgraded heads, injectors, intake and throttle body. However, pro's like Holdener are quite savy and realize that cams are all about matching specs to the engines requirements, and therefore the manufacturer's marketing intentions for use in an EFI motor are simply not a barrier!
The XFI cam was swapped into place and another set of dyno runs made. The XFI showed peak gains of 29 horsepower and 27 ft-lbs of torque. Some might point out the cam duration and lift were greater with this cam than the original, but in fact the engine did not lose any power down low compared to the Xtreme Energy cam, and made peak power and torque at the same rpm! That is pretty impressive in our book, and has us convinced that the Comp XFI cams are worth consideration if you are building a small block Ford stroker, carbureted or EFI.
Richard Holdener has published this dyno test and hundreds of others in his excellent new 144 page book "
Dyno-Proven Small-Block Ford Performance" published by
Cartech.
Fig 1: Horsepower comparison: Xtreme Energy vs. XFI
Fig 2: Torque comparison: Xtreme Energy vs. XFI
Images and Figures courtesy of Richard Holdener and Cartech. Use of images without their permission is strictly permitted.
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