1956 Packard Panther Project

Panther "Restomod" Projects

Engine Computer Simulations

Since almost no one is hot rodding Packard V-8s these days (few ever did) and information from the factory is unobtainable, I decided to use modern computer engine dyno simulation software (Dyno2000 version 3.10) to get closer to an "optimum" equipment choice for my Panther engine.

The major components that I can realistically vary (and parameters I can simulate) are these:

  • Displacement: starting at 352CID and given the stock crankshaft, how much displacement can I safely achieve? Probably 374CID (+0.125") is the reasonable limit.
  • Compression ratio: This will vary between 8.5:1 and 10.0:1 depending following the displacement increase and piston configuration. Today's highest octane pump gas will limit me to 10.0:1 maximum.
  • Camshaft: Since I can regrind the stock cam, I can get any flat-tapped hydraulic profile that can be ground on that core. This can be anywhere from very mild (stock) to fairly wild (race-only).
  • Carburetion: This will vary from 457CFM for the rebuilt Carter 4bbl on my Executive parts car to 1,000CFM if use a Caribbean 2x4bbl (single plane intake manifold with a pair of 500CFM Edelbrock Performer or equivalent carbs). Reasonable in-between values available from Edelbrock as single 4bbl (dual plane) are 600CFM and 750CFM.
  • Intake manifold:The 1955-56 Caribbean 2x4 intake manifold is much higher performance than the 1x4 intake manifold. Fortunately, I obtained one for the Panther Project engine. I do not have the original Rochester 4GC carbs or "Bat Wing" air cleaner, but those are easily replaced with modern "hot rod" pieces.
  • Exhaust system: I can install a totally stock dual exhaust system (not so good as you will see below) or fabricate custom headers and exhaust system (great, but time consuming and expensive).

To start with a simulation baseline, I'll assume the advertised HP & TQ of a 1956 Clipper or Executive 352CID Carter WCFB 4bbl (457CFM) with dual exhaust. We all know these numbers were "gross" values and maybe were "tweaked" for advertising purposes, but I'm only interested in RELATIVE performance.

Packard claimed these numbers:

275HP@4600 & 350TQ@2800 Advertised

Plugging the stock parameters into the simulation software yields:

257HP@4500 & 351TQ@3000 Baseline

This is -18HP & -1TQ from advertised but is actually pretty close to the advertised rating of the 1955 Senior 352CID with 1x4 intake manifold and one Rochester 4GC carburetor (408CFM) at -3HP & -5TQ difference. Whatever.... This is close enough for my purposes and is my BASELINE. All subsequent changes are deltas (usually additive) from these values. The following is a summary of what the dyno simulation claimed were the delta changes.

CHANGING DISPLACEMENT from 352 CID to 374CID (simulate using dished pistons to keep the C.R. at 9.5:1 constant while increasing the displaced volume only) yields:

257HP@4500 & 371TQ@3000
This is 0HP & +20TQ from BASELINE.

CHANGING COMPRESSION RATIO from 9.5:1 to 10.0:1 (simulating going back to flat top pistons) yields:

264HP@4500 & 379TQ@3000

This is +7HP & +8TQ delta and +8HP & +28TQ from BASELINE. This just confirms the old hot rodding adage "bigger is better" (displacement & compression ratio together). I will have to pay more for premium gas though.

CHANGE CAMSHAFT from stock to Lazer regrind yields:

310HP@5000 & 388TQ@3500

This is +46HP & +9Q delta and +53HP & +37TQ from BASELINE.

CHANGE CARB from stock (487CFM) to Edelbrock (750CFM) yields:

328HP@5000 & 397TQ@3500

This is +18HP & +9TQ delta and +62HP & +46TQ from BASELINE.

CHANGE INTAKE & from 1x4 stock (dual-plane, 487CFM) to 2x4 Caribbean (single plane, 974CFM) yields:
349HP@5000 & 397TQ@4000

This is +21HP & 0TQ delta and +92HP & +46TQ from BASELINE.

CHANGE STOCK EXHAUST MANIFOLDS to small tube headers (custom fabrication).
CHANGE STOCK MUFFLERS to high performance mufflers ("Flowmaster") while I'm at it yields:

--->402HP@5000 & 453TQ@4000<---

This is +49HP & +50TQ delta and +145HP & +102TQ from BASELINE. This shows how bad the stock cast iron "log" exhaust manifolds are. The mufflers only accounted for +4HP & +6TQ of this change.

That performance will do, especially if it's anywhere near real!

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