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Kostecki Engine Centre tests CHI 3V heads against CNC ported iron 2V heads.

CHI's aluminium 3V goes head to head against the trusty iron 2V on KEC's engine dyno.

Kostecki Engine Centre recently conducted a back-to-back test between these two Cleveland heads to determine relative efficiencies, ultimate power and bang for the buck. The results were surprising.

Method

Fundamental to this test was having two short motors that would draw exactly the same air speed through each test head. Building two identical short motors was the first step, but standardising airspeed was a totally different matter. It was necessary to plot the camshaft area under the lift curve in relation to port velocity. This then enables KEC, to select camshaft specs for each engine in order to try and establish as level a playing field as possible for each engine. The 3V ports were larger than the 2V, so it was necessary to give the 3V engine a cam with slightly more lift and duration.

Combinations

Both engines had 3.5-inch strokes & 4.030-inch bores to give 357 cubic inches of displacement. Inside, both engines housed 4MA cranks, standard rods, ARP main studs as well as rod bolts and flat tappet camshafts. Compression in the 2V motor was a mild 9:5-1, while the 3V ended up with 10:5-1, due to the high detonation tolerance of alloy. The 2V camshaft had 230@ .050 on the intake and exhaust with .530-inch valve lift and 108 degrees of lobe separation. The 3V camshaft was slightly bigger ( in order to try and even up the air speed with the 2V) with 235@ .050 on the intake, and 239 @ .050 on the exhaust, with a total valve lift of .560-inch and the same lobe centers as the 2V - 108 degrees.

Testing

KEC's super flow engine dyno was working overtime during testing, as each engine was run-in and had their respective jetting and ignition curves optimised. After tuning each engine it was obvious that both motors were running very efficiently. As they both required the same amount of timing: 18 degrees of static and a relatively low, 29 degrees of total. In fact pulling the 2Vs timing back from 35 to 29 netted 15 hp.

First in to bat was the 2V, which produced a very stout 438hp@ 6200rpm, with peak torque reaching 393 ft/lbs @ 5200rpm. Next up was the 3V which breathed deeper to produce 504 hp@ 6800rpm and 401 ft/lbs of torque at 5200rpm.

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Conclusion

Although the 3V produced more power than the 2V, that is not the entire story. To make more accurate comparisons, the volumetric efficiency and brake specific air and fuel consumption figures must be examined. The 2V clearly uses more air to produce its power than the 3V. However the 3V has very similar brake specific fuel consumption to the 2V. Basically, this means that the 3V is a more efficient cylinder head than the 2V in terms of the power it produces from the air and fuel that it consumes.

A quick look at the relative volumetric efficiencies tells a slightly different story. Although the 3V is efficient, it could be made even more so with a larger displacement engine or a camshaft with longer duration. Both of these alternatives would induce higher port velocities and a corresponding increase in volumetric efficiency. Whereas the 2V has VEs that start in the high 90s and brake into the 100s; the 3V begins in the high 60s and never quite reaches 100%. Manifold plenum volume is also a factor in this equation, and the TFC 4V manifold was specifically designed for high RPM or large displacement type Cleveland applications, hence the plenum is too large for a standard displacement engine. This contributes to the lower port air speed and lower VEs.

As a bare back to back test though, the results are very interesting, proving that CNC 2V heads are capable of producing strong power and high VEs in standard displacement Clevelands . Start looking for a bit more though, and the alloy heads are the natural choice. They are perfectly suited to 377 cube + displacement engines, and matched with the appropriate camshaft and compression ratio the 3Vs will see you into the 650hp zone.

Click here to view 2V dyno data

Click here to view 3V dyno data

2V on Dyno

2V cylinder head has fully CNC machined combustion chambers and ports

3 V on Dyno

Fully CNC machined 3V is a work of art

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