Packard Forum Index » V-8 (1955-56)

Hi, Craig,

Thanks for the clarification. If you have already posted the air flow data for the '56 Packard heads, my search didn't find it, so appreciate you pointing me toward it. If you haven't posted them would you share them now?

thnx, jack vines

Jack,

Not posted anywhere on Packardinfo.com. Here they are:

<h2>Packard V-8 head air flow</h2>
<p>
Testing performed Sept 4, 2000 in Orange, CA by Pete McCarthy. Test performed
on a Superflow 600 Bench at 25in of water.
</p>

<table border=1>
<tr><td><b>Intake port</b></td><td></td><td></td></tr>
<tr><td><b>Lift</b></td><td><b>55 Pat</b></td><td><b>56 Est</b></td></tr>
<tr><td>0.100</td><td>65</td><td>67</td></tr>
<tr><td>0.200</td><td>105</td><td>108</td></tr>
<tr><td>0.300</td><td>138</td><td>142</td></tr>
<tr><td>0.400</td><td>167</td><td>172</td></tr>
<tr><td>0.500</td><td>180</td><td>186</td></tr>
<tr><td>0.600</td><td>184</td><td>190</td></tr>
<tr><td>0.700</td><td>190</td><td>196</td></tr>
</table>
<table border=1>
<tr><td><b>Exhaust port</b></td><td></td><td></td></tr>
<tr><td><b>Lift</b></td><td><b>55 Pat</b></td><td><b>55 good seat</b></td></tr>
<tr><td>0.100</td><td>25</td><td>50</td></tr>
<tr><td>0.200</td><td>77</td><td>80</td></tr>
<tr><td>0.300</td><td>110</td><td>110</td></tr>
<tr><td>0.400</td><td>129</td><td>129</td></tr>
<tr><td>0.500</td><td>138</td><td>138</td></tr>
<tr><td>0.600</td><td>144</td><td>144</td></tr>
<tr><td>0.700</td><td>146</td><td>146</td></tr>
</table>

Hi, Craig,

Thanks again. Just confirming Quote: as 28" is the more typical standard today.

thnx, jack vines

Multiply all numbers by 1.06 to get 28in H2O. Dyno2000 will take the flow numbers either way.

Craig

Jack and Craig,

Some of these specs are beyond me, but they mean a lot to some technical folks who can appreciate them.

I'm back in the dark ages of HP and Torque. I have the published figures for the Packard 352, and wonder if the same categories are easily obtained for the 348 W ? I think that engine would be most comparable to the 352 Packard, and most likely to be the "platform" on which Chevy might have decided to base an engine. So I vote for 352 vs 348 comparison using the same spec categories as Packard offered.

I understand those spec categories (and VE somewhat) but this is the one that gets me:

What the heck is Maximum B.M.P.E., lbs/sq in 152.1@ 2600 rpm??

I will also continue to look around for 348 W Chevy specs.

(Mere hours later...)

Well, that didn't take long. It's not as exhaustive as the Packard list, but it's a start.

1958 Chevy 348 with 4 bbl
Bore & Stroke 4.125 x 3.25
Compression Ratio 9.50:1
HP 250 @ 4400
Torque 355 @ 2800
Firing Order 1-8-4-3-6-5-7-2
Weight* 655
*According to "Super Cars" December 1978
(All other specs from "Carnut" web site)

Since they're back on a previous page, here for your convenience are the Packard 352 figures:

Bore 4"
Stroke 3.5"
Stroke-to-Bore Ratio .875
Displacement 352 ci
Compression ratio 8.5:1
Designation of Cylinders:
Left F-R 1-3-5-7
Right F-R 2-4-6-8
Firing Order 18436572
Maximum Gross Brake HP 260 @4600 rpm
Maximum Gross Torque 355 ft/lbs @2400-2800 rpm
Maximum B.M.P.E., lbs/sq in 152.1@ 2600 rpm
Piston Travel 1480 ft/mi
Engine weight 698 lbs

According to this, even though the Packard gives up a full point on compression ratios, it bests the Chevy by about 10 HP at 200 higher rpm and has identical torque in a range starting 400 rpm lower than the Chevy and, according to the specs, staying in that range up to the same rpm where the Chevy peaks

It does all this while weighing 43 lbs more than the Chevy (although weights can be measured under so many different configurations, it's pretty hard to tell.

Maybe Chevy decided they wanted something that would behave very much like the Packard!

Now here's a question. Chevy started touting later editions of this engine as the "Turbofire", which I thought they meant to indicate was something new in the firing order--but all the BBs had the same firing order. The SBC, too.

Why use the '55 Packard specs to compare to a '58 Chev? The '56 had 9.5 C.R., slightly larger valves, slightly more camshaft duration and lift, giving 275 horsepower.

thnx, jack vines

So what would somebody like to see? I don't have a lot of time to spend tweaking these sims. But, on the other hand, it would be interesting to see something relevant simulated.

Craig

Jack, I believe you speak well for the '56 352, but I would say the '55 352 vs the 348 already shows the Packard to be remarkably close in performance, given it had not yet had the '56 improvements. The fact that the '55 352 gives up a point on compression makes the outcome of the spec comparisons that much more impressive. Chevy gets a "head start" so to speak in CR and winds up in a dead heat on almost all other fronts.

The other reason I chose the '55 is, I don't have these figures for '56, do you?

These are the figures that the 352 and the 348 4bbl "premiered" with although the Chevy came out 3 years later.

Craig,

If you're willing to do the simulations using the heftier specs for the '56 352, that would be great.

All I had for apples-to-apples printed specs were the '55 352 engineering paper and the "Carnut" figures for the '58 Chevy.

Jack makes a good point that the engine that Chevy probably would have started with was the '56 352.

The only other sort of viable comparison would be 374 vs 409. I'd be curious to see how they stack up. Dual quad vs six-pack.

I think at least part of the original question is already answered. If Chevy had wanted to pay for the Packard big block design and tooling in 1958 instead of putting together their own rather odd and ultimately abandoned "W" design, they would've probably done well. Of course, one reason for abandoning such an idea, in any corporate setting, is the engineering stigma of "not invented here" and also the bad press that was bound to circulate--"Chevy buys Packard Big Block V8 design, admits it's better than anything they could come up with. Packard still goes broke."

I'm pretty well convinced that the lower compression '55 Packard 352 shows it already would have been a more than worthy substitute for the '58 Chevy 348 4bbl.

" in any corporate setting, is the engineering stigma of "not invented here" and also the bad press that was bound to circulate..."

During the 50's and thru the late 70's US corporations received nearly a 100% tax write off for R&D operations. They actualy made money from it. So it would not have been financialy beneficial to buy from other companies unless there were issues to consider such as tight time frames.

<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>