Join Date: Jan 2019
Location: Sedgwick, Kansas
What's your intention for this car? Track only? Drag racer?
That carb is overkill unless you're running at 7k RPMs. It *might* be okay on the top end going WOT, but at low RPMs and part throttle, you might as well be using a small garden hose to dribble gas down your intake. Throttle response and economy will suffer, so it would be a poor choice on the street, where a 289 really needs something around 500 CFM.
Your giant valves are a similar compromise; at top RPMs, it may help your peak horsepower, but the low velocity involved with those manhole-sized 2.018 intakes is going to make it a real dog for in-town driving.
If it's a strip terror, and you're running 4.10 gears with a manual transmission, this thing should be pretty fun! Your actual horsepower would depend a LOT on the cam, as well as some other parts you haven't got listed, like your headers. I'm kind of surprised you didn't go with a single-plane manifold too, since everything else is geared to ignore low and midrange on this build, in favor of a wicked top end charge. That being said, the Stealth should probably still do okay for you, with at least a 1" open carb spacer on it to give you a bit more plenum volume and allow some pulse transfer between sides. In fact, with your oversized carb, the Stealth may end up being a slightly better choice for your 289. It's probably a close call.
Assuming you went with a 'racy' cam designed to put you around 7k (you didn't mention roller lifters or rockers, so that's probably end of the line if you're running flat tappets) I am going to take a wild guesstimate and say you're going to be around 350 flywheel horsepower, with really horrible street manners and mileage that will even make 500 Caddy drivers feel economical.
Your *peak* horsepower might be decent, but average horsepower will probably be way down, due to the short stroke and corresponding lack of low-end torque, along with the high-rpm-only goodies on this engine.
I am guessing you meant domed pistons (-18cc) not dished (+18cc) to get that compression ratio; I hope they are well matched to your heads so you can take advantage of quench, or this thing is going to need avgas to run!
Good luck, and hope it's wicked fun. =)
Last edited by Grimbrand; 05-18-2019 at 06:36 AM.