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Rebuild info | Engine Carburetor Estimator | Performance Estimator

Engine Rebuild Notes:

Before the restoration: all original everything, down to the belts and plugsMy Boss, like many other Bosses, spent it's life as a Super Stock drag race car. After spending it's first year running down track it was rebuilt. Most importantly, the crank was turned down 10 mils. Although this is done typically in a rebuild, this does make the bottom end a little weaker. When we decided to freshin up the motor, (Jan. of 2003), we decided to store the original crank, rods and pistons, and replace them with a stoked crank setup which gave it 515 cubic inches. Since I still plane to run the Boss-9, and hearing some horror stories, I didn't want to risk it.

Boss-9 on dynoThe heads were preped and then flow tested. A new specially ground camshaft was designed based on the flow test results. Compression remains the same at 10-to-1 (I still want to use pumped gas).

The rest of the engine remain stock w/ most of the orginal hardware, including all hoses. It's amazing that after 34 years on the car most all of the rubber is still very plyable.

The only item that looked like it was missing from the engine was a tower Wittek clamp on the J-house on the bottom of the air pump. We noted no marking or indents on the camp, indicating that there was never one their to begin with. I guess someone missed this during it's assembly.

More will come w/pics....

This has both positives and negative.

    Positives:
  • Stronger bottom end
  • Better Stroke / Bore ratio: 4.25"/ 4.39"
  • More cubic inches (515 CI)
  • More lower end torque (nearly 600 ft-lbs)
    Negatives:
  • Need more carburetion (@ 6,500 need a calculated 1,005 cfm @ 83% VE)
  • Calculated max RPM 4,800 before the carburetor chokes

Engine Carburetor Estimator

Volumetric Efficiency (VE):

If an engine could have 100% volumetric efficiency, it would draw in a volume of air/fuel mixture equal to its displacement times 1/2 its speed. Because of those pesky laws of physics, an engine normally can't do that. The percentage of "perfect" airflow that the engine actually draws it called its "volumetric efficiency," or VE. VE is affected by intake type, camshaft grind and type, boost, and many other factors.
  • Factory engine: 65%-75%
  • Mild street performance, flat-tappet cam: 80% - 85%
  • Mild street performance, roller cam: 90% - 93%
  • All-out race engine, 95%-105%, depending on cam type and operating RPM range. Long, high cams operating at higher rpm's yield higher VE.
  • Blown engines, typically over 100% or higher, depending on amount of boost.

Manifold Efficiency:

Since losses exists in the induction system, a larger volume of air/fuel mixture needs to be available.

  • Daul-plane characteristics induction system 67% - 83%.
  • Single-plane characteristics (single planes, tunnel rams, etc.): 77% - 90%
 Calculate DescriptionValue
Engine Displacement (CI)
Engine Max Speed (RPM)
Volumetric Efficiency (%)
Manifold Efficiency (%)
Carburetor Size (CFM)

Performance Estimator

This program calculates approximate rear wheel horsepower based on actual vehicle weight (including driver), and quarter mile elapsed time and trap speed. Two formulas are used: One uses weight and e.t, the other uses weight and speed. This program calculates both and averages them.

To Calculate the "Approx. Engine HP" we have to estimate parasitic (drivetrain) losses (25% would be typical). Obviously, there are a lot of variables unaccounted for.

Performance Calculator

 Calculate DescriptionValue
Car weight w/driver (lb.)
ET (sec)
Trap Speed (mph)
Rear wheels (hp)
Parasitic Losses (%)
Engine (hp)