Originally Posted by Techwest Racing Services (Post 329702)

GTX JOHN

The MSD HVC coils are a faster reacting coil than the Pro Power 8201 coil. The retarding of timing is a side benefit of the HVC coil, less timing in the engine with better performance.

Originally Posted by Techwest Racing Services (Post 329948)

MEXJOE

Short answer combo does not matter. If you hook up the box & coil on the bench with an oscilliscope. Then vary the sparkplug gap from narrow to very large you would find that the MSD 8251 coil is very fast reacting coil when compared to the MSD 8201 coil. We repeated this same kind of testing over the past couple of years during dyno testing. The results were the same the MSD 8251 coil was a better match to the 7 series boxes. Thanks for the great question! :)

Originally Posted by Techwest Racing Services (Post 330078)

Lew Silverman

Yes, the MSD 8253 is a good match up to the MSD 6421. Many of our customers use that combo in their racing program with good results.

Originally Posted by Techwest Racing Services (Post 330080)

MEXJOE

Ok, now we are on the same page! :) Let me start with, as a common practice when using Dyno time to dial things in. Consider bringing and using your ignition setup to tweak things in. The two setups you mentioned should provide different results if your there to tweak the engine in. If your there to just see what numbers the engine can pull then just run what they have hooked to the dyno. As for moving the timing, each engine has its own personality and will have its own sweet spot. Most of our customers find that they only need to move one degree of timing when tweaking things in.