Moving on to the Mopar Chrome Box, we wondered if it would cure the timing retardation we saw with the Orange Box. The step in the torque curve was still there but it had moved by a slight amount. With several attempts at curing the power loss again failing, we again ended up at 32 degrees total with a slight increase in power. Our averages with the Chrome Box were 504.4 lb-ft and 478.9 horsepower. That's a total increase of the "stock" box of 15.7 lb-ft of torque and 15.6 horsepower.

We were finally ready to try the new Rev-n-Nator unit from The R/T Garage. Installation was as simple as the other plug-in boxes, with one minor exception. There is a small external ground wire that needs to be attached to the chassis ground to help ensure a good ground. Next, you simply turn the ignition to Run, and push the small button once for each rev limit-setting number indicated by the small LEDs on the front. These are the settings for the rev limiter.


  • 1 = 3,000 rpm
  • 2 = 5,000 rpm
  • 3 = 5,500 rpm
  • 4 = 6,000 rpm
  • 5 = 6,500 rpm
  • 6 = 7,000 rpm
  • 7 = 7,500 rpm

A nice bonus is that these LED indicators also represent a digital tachometer while the engine is running: 1=1,000 rpm, 2=2,000 rpm, etc.

With the rev limiter set at 7 to make sure we would not run into issues while making power pulls, we ran the 421 through another timing loop. This time we settled on a slightly lower reading of 30 degrees total timing for our best power. With new bests of 513.8 lb-ft of torque and 487.4 horsepower, to say we were impressed is an understatement. We also noted that the timing did not retard throughout the rpm range like the Mopar boxes did, and the torque curve was the smoothest we had seen.

We talked to Troy at The R/T Garage and he explained a few things. The way his ignition box picks up and processes the signal from the distributor is completely different from the technology used when the Mopar boxes were designed. The older boxes did not have any sort of intelligence to modify the incoming signal and manipulate it to get the best performance. This is how he was able to get performance increases. But it does mean you may have to adjust your timing in some cases due to differences in how strong of a signal you have.

The R/T Garage
Dunnuck Racing Enterprise