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1965 Impala SS 409cui performance


Gert Frost
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Hello,

 

I have a 1965 Impala with a 409 engine with TH700R4, an Edelbrock 1406 3110 carburetor and HEI distributor.

I had it dyno’ed, and the result was an estimated 207 hp at the crank (corrected for loss in driveline). As it is rated at 340 (I’m aware that the 340 and tje 207 is not “completely” comparable), I tried to measure the cylinder pressure - it came out consistently with 125psi/9bar on all cylinders.

I have no knowledge of the internals of the Edelbrock - but does anyone in here have a possible explanation for the missing power?

93F2C625-C33C-4A90-AB8A-92AC9C72171A.jpeg

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So this actually a "crank" horsepower number converted from a measured rear wheel HP. I'd first ask where that conversion factor came from and how was it validated? Unless the dyno operator ran consistent back-to-back tests on the wheel dyno and an engine dyno with exactly the same engine and the same drivetrain as your car, and properly compensated for weather conditions, that "conversion could be off by plus or minus 50%.

 

Other things to consider are 1) the 1406 is only a 600 CFM carb, which is small for this engine. 2) what cam is in the motor? 3) was the converter locked or not? 4) what stall are you running in the converter? 5) what exhaust are you running? 6) what accessories are you running?

 

There are a bazillion variables here, and the RWH to crank HP conversion it the biggest one.

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