A large fan is used to supply air to the Pontiac's radiator while on the chassis dyno. | 
The Edelbrock 650 carburetor took on a slightly different personality with the engine in the Bird. It was found to be very rich at a cruise speed of 30 and 60 mph (12.2 to 12.5:1) while going very lean (15.2:1) at full throttle. | 
The first step was to confirm that the ignition timing was still at the 31 degrees before top dead center (BTDC) total, as that was found to be the best setting on the engine dyno. Technician Scott Roschel manned the timing light while Bob Wise raised the engine rpm. The total was only 27 degrees BTDC, so the distributor was brought to the proper value before a dyno run was made. |
The shop's DynoJet chassis dyno features the latest and most advanced software and the computer is kept in a sealed case for reliability. Here, Bob is setting the parameters for the test. | 
Scott did all the testing/driving on the dyno while Bob monitored the outputs. A number of initial runs were made to confirm accurate data before tuning. All testing was done in high gear. | 
With the mixture too rich and then too lean, the engine produced 230 horsepower at the tires with 31 degrees timing. We all knew that a proper fuel curve would pick that up. |
The first tuning decision was to lean out the part-throttle operation with a swap of metering rods. | 
A metering rod with a thicker first step (less fuel at cruise) and the same dimension second step was installed. This one change created a cruise mixture of 14.2:1 and was considered perfect for the low-compression Pontiac. The original metering rods measured 0.068 and 0.047 inch (first and second step, respectively) and were switched to a pair that was 0.074 and 0.047 inch. | 
Craig Wise, the in-house carburetor tuner, felt that a secondary jet change was required to richen up the full throttle fuel curve. Scott worked quickly, but carefully, to remove the carburetor from the engine. |
| 350 Pontiac Chassis Dyno Test |
| Dyno testing was performed using 93-octane fuel. |
| RPM | HP | Torque | Air/Fuel Ratio |
| 3,400 | 149.51 | 230.86 | 14.35 |
| 3,600 | 189.62 | 276.61 | 13.89 |
| 3,800 | 207.45 | 286.74 | 13.58 |
| 4,000 | 219.19 | 287.82 | 13.34 |
| 4,200 | 230.46 | 288.19 | 13.20 |
| 4,600 | 242.45 | 276.78 | 13.02 |
| 4,800 | 250.71 | 271.81 | 13.08 |
| 5,000 | 249.10 | 261.55 | 13.02 |
| 5,200 | 247.92 | 250.50 | 12.85 |
| 5,400 | 226.53 | 220.36 | 12.81 |
Note: This test was performed with no air filter in place.
Once the air filter was attached, the engine picked up
slightly over 2 horsepower at peak to 252. |
ConclusionIt cost $4,842 (plus $400 for dyno testing) to build this 350 that puts 342 hp to the flywheel and 252 rwhp to the ground reliably. Thanks to forward thinking on Bob Wise's part, the heads flow enough to support more cam, more carb, and more power, should Jason decide to go there in the future.
In the end, the Korb family received what they asked for. Their '69 Firebird not only looks great, it also has a potent, yet smooth, Pontiac 350 engine that should make it stand out in a sea of 400 and 455 cars at the shows and cruises. "There is a night-and-day difference between how the Bird was before and after the engine swap," explained Jason. "The power is spectacular for a 350, it launches beautifully when you ease into the throttle, or you can make it go sideways if you mash it! Since I swapped in the 200-4R, the Firebird is more highway friendly as well. Now I drive it as much as I can because it performs so well and is comfortable at highway speeds."
Let's not forget what chassis dyno tuning can do, either. This Bird made 230 rwhp when it arrived, and left making 252 rwhp after dialing in the carb to better match the drivetrain. A 22 hp increase and proper air/fuel ratio at full throttle and cruise are certainly worth the effort.