Re: Did Chevy consider Packard V8 BB Design?

Posted by Craig Hendrickson On 2008/10/12 11:13:38

<h2>Packard 1956 352 vs Chevy 1958 348W</h2>
<h2>Engine parameters, base engines</h2>
<table border=1>
<tr><td><b>Param</b><td><b>Packard 352</b</td><td><b>Chevy 348</b></td></tr>
<tr><td><b>Bore</b><td><b>4.000</b</td><td><b>4.125</b></td></tr>
<tr><td><b>Stroke</b><td><b>3.500</b</td><td><b>3.250</b></td></tr>
<tr><td><b>Int size</b><td><b>2.000</b</td><td><b>1.9375</b></td></tr>
<tr><td><b>Exh size</b><td><b>1.635</b</td><td><b>1.656</b></td></tr>
<tr><td><b>Head style</b><td><b>inline</b</td><td><b>semi-cant</b></td></tr>
<tr><td><b>Comp ratio</b><td><b>9.5</b</td><td><b>9.5</b></td></tr>
<tr><td><b>Carb</b><td><b>WCFB</b</td><td><b>WCFB</b></td></tr>
<tr><td><b>Exhaust</b><td><b>dual</b</td><td><b>single</b></td></tr>
<tr><td><b>Adv HP</b><td><b>275</b</td><td><b>250</b></td></tr>
<tr><td><b>Adv TQ</b><td><b>350</b</td><td><b>355</b></td></tr>
</table>
<p>The Chevy intake exhaust sizes are now correct for the 1958 348 engine.
The larger sizes used in the previous simulation were for the later 348.
</p>
<h2>Camshaft specs</h2>
<table border=1>
<tr><td><b>Number</b><td><b>6480561</b</td><td><b>3744901</b></td></tr>
<tr><td><b>Type</b><td><b>Hyd</b</td><td><b>hyd</b></td></tr>
<tr><td><b>Int dur</b><td><b>256</b</td><td><b>272</b></td></tr>
<tr><td><b>Int lift</b><td><b>0.398</b</td><td><b>0.400</b></td></tr>
<tr><td><b>Int CL</b><td><b>114</b</td><td><b>112</b></td></tr>
<tr><td><b>Exh dur</b><td><b>252</b</td><td><b>280</b></td></tr>
<tr><td><b>Exh lift</b><td><b>0.388</b</td><td><b>0.412</b></td></tr>
<tr><td><b>LCA</b><td><b>111</b</td><td><b>112</b></td></tr>
</table>
<p>Both manufacturers have suspect duration numbers.
I found specs for a F-M CS-171 replacement for the 3744901 cam,
but those seat-to-seat duration numbers shown above produced results that
were way higher than the advertised HP and TQ numbers. The 0.050 lift
duration was 190 and 198, which gave results closer to the advertised HP
and TQ values, so I used that. Ref is <i>How to build Classic Hot Rod V-8
Engines</i> by George.
</p>
<h2>Volumetric Efficiency, percentage</h2>
<table border=1>
<tr><td><b>RPM</b><td><b>Packard 56 352</b</td><td><b>Chevy 58 348</b></td></td></tr>
<tr><td>2000</td><td>69.0</td><td>72.3</td></tr>
<tr><td>2500</td><td>70.6</td><td>73.7</td></tr>
<tr><td>3000</td><td>74.1</td><td>76.9</td></tr>
<tr><td>3500</td><td>76.5</td><td>78.3</td></tr>
<tr><td>4000</td><td>77.2</td><td>77.6</td></tr>
<tr><td>4500</td><td>76.1</td><td>75.7</td></tr>
<tr><td>5000</td><td>73.1</td><td>71.2</td></tr>
<tr><td>5500</td><td>69.0</td><td>66.3</td></tr>
<tr><td>Sim HP</td><td>274</td><td>254</td></tr>
<tr><td>Sim TQ</td><td>358</td><td>356</td></tr>
</table>