Supposedly bigger plenum is better with smaller carbs, big carbs small plenum. If it’s too big car will not launch hard or be lazy on gear changes. I have some articles from bill jenkins and they greatly reduced plenum volumes even though they were way over 8000, but the engines were small and short stroke. Lot of give and take I guess. Also length and what harmonic wave you’re aiming for makes a big difference. Play with this calculator for tuned rpm ranges
