427ci C7 Corvette aka WEAPON7

We have two new parts to review after installation on our in-house 427ci C7 Corvette, more affectionately known as Weapon7.  With the exhaust side of the engine being pretty well sorted, we will be investigating other avenues for improvement on this engine combination. In the never ending search for more horsepower, we looked a little closer at the induction side of the engine. 

PARTS INSTALLED:

MSD Atomic Air Force LT1 Intake Manifold (IM)

Nick Williams 102mm Gen V Throttle Body (TB)

TESTING AND RESULTS:

(MSD Atomic Air Force IM)

Testing of the MSD Atomic Air Force revealed a few things: the stock IM design flows very well up to around 5k even on a 427ci, but the the MSD Atomic walks away from the stock manifold when more airflow is required in the higher rpm range.

After retuning for the intake manifold, the 427 LT1 made an additional 35rwhp and 25ftlb of torque over 5k rpm. Horsepower and torque were very similar in the mid to low rpm range, but the IM really woke the engine up in the upper rev range.  At 6800 rpm, the LT1 made 584rwhp and 482ftlb.

(Nick Williams 102mm TB)

Next up was the Nick Williams 102mm TB, which took all of 15 minutes to install on the dyno.  A few preliminary changes were made in the calibration to have a smooth start-up, and we were off to the races (err, dyno pulls).  The larger TB did not have any drivability issues, as power delivery is still quite smooth. 

Since the NW 102mm has a 40% larger maximum surface area, more tuning is required to really dial in the proper AFRs at WOT, but the changes were predictable and only took two pulls to hit our target.  After all was said and done, the NW 102 netted us an additional 16rwhp and 12ftlb of torque.  The increased TB area led to gains over the previous test (IM only) beginning at around 4600 rpm and climbed from there. 

CONCLUSIONS:

Our final numbers were an even 600rwhp and 494ftlb.  The combined gains of the IM/TB pair

were +51rwhp and +37ftlb with no decrease in torque down low.  Power delivery is still silky smooth on the high revving 427 LT1, and we believe the ease of installation and tuning should make this combination an easy choice to make if searching for more streetable all-motor horsepower for your build. The next modification to be tested for this combo is to port-match the intake manifold runners to the heads.  There could potentially be turbulence in the system at this point, and an increase in air velocity will probably lead to more power.  We will keep you posted.