As the author, I never publicly stated a goal for this engine. But in my mind, I set a minimum that I would feel qualified as a success. Given the fact that in production form a TPI 350 was rated around 245 hp and 345 ft-lbs of torque, I felt if our engine produced about 100 more than those figures, idled at 750 rpm, and ran on pump gas, no one could consider it anything but a success.
Three hundred and forty-five hp would have beaten a stock LT1 and placed it right at the level of a production LS1. Since the GMHTP/RaceKrafters engine employed production GM Vortec cylinder heads and factory-style induction system, results in that range would be very pleasing. Our engine would allow an old F-body or C4 to run right with a new version at the drag strip, for substantially less money.
With the little 355 sealed up, the oil changed and the DFI system dialed-in by Bob Wise, the final numbers were in. How does just shy of 420 hp and 490 ft-lbs strike you? That is correct, Something Old, Something New (SOSN), blew us away by producing almost 175 hp and 145 ft-lbs of torque more than a production version. In addition, the 355 made 15 more ponies and nearly 90 more ft-lbs of torque than the much-lauded C5 Z06's LS6 engine! I do not care what camp your loyalty lies in, you just have to love this little 355. To boot, it only wanted 26 degrees of ignition timing (This will promote good octane tolerance), idled like a stocker at 700 rpm, and at peak torque was so fuel efficient it had a BSFC Of 0.40.
What was especially interesting about this engine was that from 2,343 rpm to 5,970 rpm, the AVERAGE torque was 454 ft-lbs! At 2,400 rpm this thing had 424 ft-lbs! What this means is the engine would be happy in variety of contrasting environments. Need to pull your race car to the track? SOSN would be happy doing that all day long in a pickup truck or Suburban. Want to run in the 11s with an older TPI car and still get 30 mpg or better on the highway? No problem for SOSN! Do you want to go to the track and play with C5 Vettes with an engine equipped with cast-iron cylinder heads and a stock-looking injection system? This engine is ready, willing and able to do all of this and more.
Being true hot rodders, stunning results are never enough. The next and final step for our project is to pull the 355 back apart and send the internal parts to Swain Tech Coatings, to once and for all prove what this technology is worth. It should be interesting.
Interestingly, ACCEL/DFI's own Dual-Sync distributor would not fit with the ACCEL high-flow runners. We used a complete MSD ignition system in its stead. Thus, we ran the EFI in batch fire mode since a cam sensor signal would be required for sequential injector firings. We could have used random sequential (DFI programmed for sequential but with no cam sensor input. In this mode the ECM chooses a random cylinder each time it starts and identifies it as number (1) for injector firings.), but other than a slightly better idle quality, there would be no benefit. | 
We broke the engine in on Penzoil mineral 20W-50 and then switched to the new Penzoil Platinum 10W-30 full synthetic for the power runs. | 
Bob used a wide-band oxygen sensor input connected to the DFI system to help dial in the VE table. The easiest method to accomplish this is to set the Target A/F table all at one value. Then modify the VE table to achieve the target air/fuel ratio. When the DFI creates the target mixture, you know the airflow for that load cell is modeled correctly. By using a wide-band oxygen sensor, the CalMap software will identify as a percentage the amount of correction. That value can be used as the amount of correction required in the VE table. The Auto Cal function of the software can also be used, but Bob did not employ it. |