AFR 195 Street head dominates GM Vortec head

Pick up any Chevy based publication and at some point in time you’re bound to see a test or comparison based around a build with the GM Vortec head. Why?.....because they are inexpensive and work a whole lot better than the 23’ heads from yesteryear. Forget the fuelie or camel hump heads, in out of the box trim the Vortec head will run circles around those heads unless they have been heavily modified by a talented head porter (at that point no longer a valid comparison as the budget wouldn’t be even close).

That fact makes the test results you see below that much more impressive because in reality GM did a pretty good job on the Vortec head, at least as far as an out of the box piece is concerned.

Lets get right to the meat and potato’s of the comparison, which by the way was independent information gathered by Hot Rod magazine in a lengthy three day dyno thrash with five cam swaps and two sets of heads (our new 195 Eliminator street head and the GM Vortec head). All five tests showed similar curves to the one below, although the other four tests were hydraulic flat tappet cams so the gains were slightly less (in the 40-50 HP range) due to less area under the curve to take advantage of the AFR’s improved flow curve. You should see this test posted as well as the other four configurations tested in one of the summer editions of Hot Rod Magazine a few months down the road. When that article becomes available, we will attach a copy of it to the info provided here. It will have even more test data for you to pour over.....

For now, enjoy the comparison and results below related to the only hydraulic roller test in the bunch.....

Regards,
Tony Mamo
R&D / Product Design Mgr.


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The specs on the test engine are as follows:

• 355 CID shortblock with approx. 10 to 1 CR (Note the AFR head had a slightly larger chamber volume netting less compression which was confirmed when each engine configuration was pump checked for cranking compression….the AFR headed combo pumped 15-20 PSI less depending on which cam was installed in the engine. The same CR would have made the results even more dramatic).
  
• Comp Cams “Thumper” series cam grind # CS283T (227 deg / 241 deg @ .050 107 LSA)
• Holley “Airstrike” dual plane intake manifold
• Holley 750 CFM Carb
• Hooker 1.75 dyno headers

Test Facility was Westech Performance group in Mira Loma CA

SF902 SuperFlow Dyno operated by Steve Brule





A few things to note here….one which is important is that the Vortec heads were fitted with Comp 918 beehive springs so valve control issues were not part of the gains provided by the test results (you can see the Vortec headed graph is very clean and smooth till 6500 where the test was terminated). The AFR heads were equipped with our standard lightweight dual springs (PN 8017) and the standard equipment lighter weight 8mm beadlock valves and also showed no signs of valve control loss in the RPM range tested.

The second thing to note of more importance in this comparison is not only was the peak to peak power gains extremely impressive (57HP delta), but note how well the AFR headed engine carried that power after peak showing an improvement of 74 HP by 6500 (unfortunately the last recorded data in the test), which by the way would be a very usable figure if you were running the AFR’s. In fact, looking more closely at the results, the AFR headed combination generated the same peak power at 62-6300 RPM (453 HP), and was still making close to the same at 6500 (449 HP) where the test was terminated. This type of power curve would encourage shift points in the 6800 range so the really huge gains available past peak (which would have likely gapped over a hundred HP by 67-6800) is all very usable power that would translate into much lower ET’s and much higher trap speeds if taken advantage of by shifting approximately 500 past peak (a rule of thumb ultimately dictated by the shape of the power curve).