Zac Mertens over at Hoonigan likes old cars and big engines. His latest mill is… a mighty one, and it’s going into the nose of his 1978 GMC Jimmy. How big of an engine are we talking about here? This is a built 572 cubic-inch monster. That’s 9.3-liters for our metric friends.

Jacob Villemain from Smeding Performance in Texas is the one building the engine. He’s done a great job of walking viewers through the process too. There are a few other videos that show it all coming together, and I highly recommend you give those a watch. But with the video above, we get to see this beast make noise and power on the dyno. It’s fantastic to see the difference subtle tweaks to timing and fuel delivery can have on total output. Jacob is very good at explaining why he makes the changes he makes. And the end result is an engine that will power what’s likely the baddest Jimmy on the block.

Final power numbers? How do 733 horsepower and 733 lb-ft of torque sound? And that’s a LOT of torque available down low too, with the torque curve holding nice and flat through the rev range. We can’t wait to see that engine plunked into the truck and firing.