Well, we swapped in a more "turbo-friendly" cam (went from 110 to 114 LSA and about 20deg less duration @.050). We also switched to the "other" Holset turbo that was laying in the parts room. The plan was to compare results with the original tests, just to verify the second turbo and check out the cam change. It didn't exactly work out that way.
Finally got back on the dyno after waiting for a couple weeks while the other class sorted out (and then blew up) a blown 355.
We chased a persistent misfire, swapped plugs and wires, and finally got some smooth pulls in. It was immediately obvious that something was different. The first turbo spooled fast, but this time the engine went into boost
as soon as we'd crack the throttle under load.
We saw 505hp / 670lb ft (!)
once, but couldn't back it up. After numerous problems, we made 3 consecutive pulls around 450hp / 510 lb ft and gave up. The engine was losing hp and boost above 4500 rpm, but the A/F ratios were right on the money. After pulling the engine off the dyno, I found the "problem".....
They say a picture is worth a thousand words...