You’ve build the engine block from the ground up. You bored it, honed it and polished and ported it. The goal – MORE POWER!!! But you are going to defeat the purpose of all that work and $$$$ buy tossing the wrong size carb with the wrong size fuel line.
So I ran across the this chart that can help.
If the CID is Carb Size Fuel Line diameter
250 – 300 480-600 cfm 5/16 ”
300 – 350 600-350 cfm 5/16″ or 3/8 ”
350 – 400 650-750 cfm 3/8″
400 – 500 750-950 cfm 3/8″ or 1/2″
There is one other consideration and that is the capacity of the fuel pump, however that can be compensated for by using a fuel pressure regulator.
950 CFM Carb
Thanks for reading
Tim
I’ll agree with Steve in that big carbs need good breathing. Back in my teen days (many years ago), I had a horsepower war with my best buddy neighbors 1975 SD 455 Trans AM vs my 1969 Charger 440.
He re-jetted his Rochester Quadrajet with three larger sets of jets. Each larger set actually caused more off the line stumble. Finally, he added headers with the larger jets, and whipped ye ol’charger.
You can’t just ‘burn more gas’.
Absolutely correct. Size does matter. Fuel line to keep that carb full. My Aussie friend bought a 67 Mustang a couple of years ago. He wasn’t sure of the 289 that was in it or how it was built but it has headers and dual 3″ exhaust and it ran….fast. But it wouldn’t ever idle properly and while idling the engine would “load up”. I asked what carb he had and it was a Holley 750. I told him to go no bigger than 600. He did and that engine woke right up. Smooth idle, quick acceleration and it felt like 100 more hp. He’s very happy but is building a 302 with roller cam and rockers. That new engine will get dyno’d with a 600 edlebrock before he installs it in the carr.
Yup Size matters and big carbs won’t help small engines.