This is somewhat subjective in nature, because the stock manifold has smaller runners and moving the carb out further causes a delay in signal between the carb and the head... so your carb may not be able to be recalibrated if you could put 24" runners on them... also stock setups are a bit 'light' in performance, so on a 1 barrel or stock supersix, you may not appreciably be able to detect an improvement if it only bumps your useable torque up 3-5 lb/ft (here's where a dyno would help, but unless you had a facility available to you to check different lengths/setups empirically, the cost to rent a facility would not pan out...)... where you start to see bigger improvements is when the engine has been modified for performance to get the best efficiency out of it, and you are tuning the engine to get the most out of a specific area (an example of this would be that a few auto manufacturers had dual runner intake manifolds on late model cars that would switch from longer runners to shorter runners depending on rpm and load so they could have better torque at low rpm, or better flow at highway speeds out of a smaller engine).

So to reiterate one of our common topics, headwork is the money maker on our engine to increase performance... so I would start there even on a stock engine so it will pay dividends when you go to improve the other components (exhaust, carb, intake, compression, etc...)...

Another item to consider, our engine already has a very fat and flat torque band so improvements in the torque side are not as great leaps when comparing the numbers say on the horsepower side... the stock 225 for my car was factory rated a whole whopping 100HP, but a nice 215 lb/ft of torque... going to my 10:1 engine I got a whole whopping 196HP, but the torque was only about 260 lb/ft.... which are big gains when comparing the base engine, and made moving the fat car a bit easier (especially when using kinder drag race gearing) but still it's not the 300-400 ft/ lbs just off idle, you see out of the V-8 numbers...

Just sayin'.

Thank You DI.

Very understandable and prioritized answer to my question. I appreciate the willingness you have to share your knowledge and experience..... If I get the insatiable itch to play with intake manifolds, I will need to warm up the engine a fair bit first.