1967 273 Horsepower Rating (Chrylser Test Results)

[69 Cuda 440]

In 1967, Chrylser Performance tested the performance of the 273, with
some different Carburetor and Camshaft combinations, to deterime Horsepower gains.

The 'stock' 273/235 engine, with 10.5-1 Compression Pistons, and stock components.

Carburetors - AFB #4294 (500 CFM)
1 7/16" Primary x 1 9/16" Secondary (Venturi's 1.063 x 1.250)

Camshaft (Mechanical)
.420 Intake / .430 Exhaust ~ 248* Duration ~ 26* Overlap

Though Factory advertised at 235 Horsepower, the adjusted rate proved 218 Horsepower (rounded off to 220 Horsepower).
-----------------------------------------------------------------------
Modification (Stage 1)

Carburetor - AFB #4298 (575 CFM)
1 7/16" Primary x 1 9/16" Secondary (Venturi's 1.186 x 1.313)

Note; This AFB Carburetor was from the 1967 383/280 HP engine.

Camshaft (Mechanical)
.429 Intake / .444 Exhaust ~ Duration 268*/276* ~ 44* Overlap

Note; This camshaft was utilized in the Chrysler Marine engine.

The adjusted rate proved 229 Horsepower (rounded off to 230 Horsepower)

A gain of 11 Horspower over the stock engine.

 

[toolmanmike]

Interesting! Thanks for posting. I am a big HP 273 fan as you may know. I am still learning about these engines. Mike

 

[Oldschoolcuda]

That is cool info. Would be interesting to know at what rpm horsepower numbers were pulled.

Oldschoolcuda

 

[69 Cuda 440]

A little fact,

The Carter AFB Model #4298 Carburetor. This carburetor was used for the
383/280 HP engines in the 1967 Plymouth Barracuda, and came through with
smaller jets.

Though rated at 575 CFM, this carburetor had .010 smaller jets in it when
installed on the 1967 383 A-Body Barracuda, because of the restrictive
exhaust system on the 1967 383 A-Body cars.

True CFM rating with the smaller jets was closer to 525 CFM.
--------------------------------------------------------------------------------

Modification (Stage 2)

Carter AFB Model #3447 (600 CFM)
1 7/16" Primary / 1 11/16" Secondary (Venturis 1.186 x 1.563)

Note; This AFB Carburetor was utilized on the 1962 Max-Wedge 413 and early-1963
Max-Wedge 426 'Stage 1' engines.

Note; The secondary throttle bore opening on the cast iron intake manifold had to
bored out to 1 11/16" (stock size 1 9/16") to accept this carburetor.

Camshaft (Mechanical)
.429 Intake / .444 Exhaust ~ Duration 268*/276*

The adjusted rate proved 236 Horsepower (rounded off to 235 Horsepower)

 

[69 Cuda 440]

Modification (Stage 3)

Still using the Carter AFB Model #3447 600 CFM Carburetor.

But the Camshaft was changed to an Engle Camshaft, Model '260' Blueprinted
.430 Intake / .440 Exhaust ~ 260*/260" Duration

 

[451Cuda]

A little fact,

The Carter AFB Model #4298 Carburetor. This carburetor was used for the
383/280 HP engines in the 1967 Plymouth Barracuda, and came through with
smaller jets.

Though rated at 575 CFM, this carburetor had .010 smaller jets in it when
installed on the 1967 383 A-Body Barracuda, because of the restrictive
exhaust system on the 1967 383 A-Body cars.

True CFM rating with the smaller jets was closer to 525 CFM.

Too bad they couldn't have figured out an efficient exhaust system for the '67s. The 280 hp rating no doubt hurt sales compared to the 396/325 Camaro SS and 390/335 Mustang GT.

Or maybe it didn't matter all that much, with the 340 out in '68.

 

[65dartcharger]

In 1967, Chrylser Performance tested the performance of the 273, with
some different combinations.

The 'stock' 273/235 engine, with 10.5-1 Compression Pistons, and stock components.

Carburetors - AFB #4294 (500 CFM)
1 7/16" Primary x 1 9/16" Secondary (Venturi's 1.063 x 1.250)

Camshaft (Mechanical)
.420 Intake / .430 Exhaust - 248* Duration

Though Factory advertised at 235 Horsepower, the adjusted rate proved 218 Horsepower (rounded off to 220 Horsepower).
-----------------------------------------------------------------------
Modification (Stage 1)

Carburetor - AFB #4298 (575 CFM)
1 7/16" Primary x 1 9/16" Secondary (Venturi's 1.186 x 1.313)

Note; This AFB Carburetor was from the 1967 383/280 HP engine.

Camshaft (Mechanical)
.429 Intake / .444 Exhaust - Duration 268*/276*

Note; This camshaft was utilized in the Chrysler Marine engine.

The adjusted rate proved 233 Horsepower (rounded off to 235 Horsepower)

Great information. Thanks, anything for 1965 HP Darts?

 

[69 Cuda 440]

No nothing on the 1965.

This performance test was done in December 1966, for the 1967 Model.
------------------------------------------------------------------------------

Modification (Stage 4)

Still using the Carter AFB Model #3447 600 CFM Carburetor

But the Camshaft was changed to a slightly bumpier profile, that was a Racer Brown unit.

 

[69 Cuda 440]

I'll make it easier to follow, with all of the performance test results.

Stock 273/235 HP Commando

Carburetor; Carter AFB Model #4294 (500 CFM)
1 7/16" Primary X 1 9/16" Secondary (Venturi's 1.063 x 1.250)

Camshaft; (Stock 1967 273 'Commando')
.420 Intake / .430 Exhaust ~ 248*/248* Duration ~ 26* Overlap

The adjusted rate proved 218 Horsepower (Advertised 220 HP rating)
------------------------------------------------------------------------------

Modification (Stage 1)

Carburetor; Carter AFB Model #4298 (575 CFM)
1/7/16" Primary X 1 9/16" Secondary (Venturi's 1.186 x 1.313)

Camshaft; (Mechanical, Chrysler Marine)
.429 Intake / .444 Exhaust ~ 268*/276* Duration ~ 44* Overlap

The adjusted rate proved 229 Horsepower (Advertised 230 HP Rating)

Note; Gained +11 Horsepower over the Stock 273 'Commando'
-------------------------------------------------------------------------------

Modification (Stage 2)

Carburetor; Carter AFB Model #3447 (600 CFM)
1 7/16" Primary / 1 11/16" Secondary ~ (Venturi's 1.186 x 1.563)

Note; Carburetor from the 1963 426 Max-Wedge 'Stage 1'

Note; The secondary throttle bore openings on the intake carburetor mounting base
are bored out to 1 11/16", to provide for a 'free-flowing intake'.

Camshaft; (Mechanical; Chrysler Marine)
.429 Intake / .444 Exhaust ~ 268*/276* Duration ~ 44* Overlap

The adjusted rate proved 236 Horsepower (Advertised 235 HP Rating)

Note; Gained +18 Horsepower over the Stock 273 'Commando'.
--------------------------------------------------------------------------------

Modification (Stage 3)

Carburetor; Carter AFB Model #3447 (600 CFM)
1 7/16" Primary X 1 11/16" Secondary (Venturi's 1.186 x 1.563)

Camshaft; (Mechanical, Engle '260' Blueprinted)
.430 Intake / .440 Exhaust ~ 260*/260* Duration ~ 42* Overlap

The adjusted rate proved 234 Horsepower (Advertised 235 HP Rating)

Note; Gained +16 Horsepower over the Stock 273 'Commando'.

Note; This Engle '260' Blueprinted camshaft put out -2 less horsepower than the
Chrysler Marine camshaft.
--------------------------------------------------------------------------------------

Modification (Stage 4)

Carburetor; Carter AFB Model #3447 (600 CFM)
1 7/16" Primary x 1 11/16" Secondary (Venturi's 1.186 x 1.563)

Camshaft; (Mechanical, Racer Brown 'ST-2')
.450 Intake / .455 Exhaust ~ 260*/260* Duration ~ 50* Overlap

High-Rate Valve Springs, #100 lbs. (Valve-Closed) / #240 lbs. (Valve-Open) are installed.

Also, Chrysler Hemi Solid-Tappets with .0005-.0015 clearance are installed.

The adjusted rate proved 243 Horsepower (Advertised 245 HP Rating)

Note; Gained +25 Horsepower over Stock 273 'Commando'
-------------------------------------------------------------------------------------------

Modification (Stage 5)

Carburetor; Holley Model #4160 / List #3575 (585 CFM)
1 9/16" Primary x 1 9/16" Secondary (Venturi's 1.250 x 1.313)

Intake Manifold; Edelbrock LD-4B (Chrysler Part #)
Aluminum Dual-Plane High-Rise

Camshaft; (Mechanical, Racer Brown 'ST-2')
.450 Intake / .455 Exhaust ~ 260*/260* Duration ~ 50* Overlap

The adjusted rate proved 259 Horsepower (Advertised 260 HP Rating)

Note; Gained +41 Horsepower over Stock 273 'Commando'.

 

[69 Cuda 440]

318 Poly,

I believe the Performance Test, was a comparison to challenge the Ford 289/225 HP and 289/271 HP 'Hi-Po' engines.

The Ford Mustang 289/225 HP 'A-Code' Engine had,

* 10.0 -1 Compression
* Cylinder Heads with 1.78" Intake / 1.48" Exhaust
* Camshaft (Hydraulic) .366 Intake / .380 Exhaust ~ 266*/256* Duration ~ 30* Overlap
* Valve Spring Pressure [#180 lbs.]
* Dual-Plane Cast Iron Intake
* Autolite Model #4100 Carburetor (480 CFM) {1 7/16" Primary x 1 7/16" Secondary}

 

[69 Cuda 440]

OldSchool,

I'll see if I can dig up RPM / Horsepower Numbers.

The 'best overall' performance engine was 'Stage 5' which was the 273/260 HP.

Another camshaft change was performed, and also with another Holley Carburetor which was 'Stage 6'.

And, finally a reworked Cylinder Head (by Kenyon) with a larger Intake Valve
was utilized for 'Stage 7', the final performance test.