[Formulajones]

Large differences like that between engine and chassis dynos are not unusual.

I see it all the time with our stuff as we have went from the engine dyno to a chassis dyno on several occasions.

An example is Dad's engine which made 724 HP on Tony Bischoffs engine dyno. We already know that to be very accurate and not inflated. It was even tested with the exhaust used on the car, no fancy dyno headers that Inflate numbers

Same engine in the car on a NASCAR certified chassis dyno that we've used several times with repeatable numbers he made 505 HP at the tires.
That's a big percentage difference but not out of the ordinary. He's pushing through a 4l80 with the converter unlocked, a heavy 3.5" steel driveshaft rated for 1000 HP and a 12 bolts rear

That whole 15 percent difference that is commonly thrown around on the internet is complete bs. You really can't put a number on it like that and you can't compare one chassis dyno to another. There are way too many variables. The key is to keep using the same dyno and make your tuning changes, that's what it's for. Going to different chassis dynos is going to throw you for a loop and make no sense at all.