350 SBC Build.

[Caleb]

So im about 6 months in my truck build and im saving up for heads before college. im running a mutha thumpr cam and a dual plane air gap intake with 4.11 posi on a 4inch lift with 35's. ive been looking at heads and im thinking about 210cc runners BUT people say its too big for my motor? they do say its a good choice for 383 stroker. however i do plan on stroking it within the next year or so so will the 210's really be that bad if i tune my motor correctly. i dont want to do this twice because i am building bare heads up with the best parts possible including roller rockers. i would think more flow would be better if you add more fuel, but this is why im asking because i dont know everything. thanks guys.

[geezer#99]

Did you put that waste of good iron cam in yet?
As for heads those might be a bit overkill but you might need them later.

[Caleb]

yes i did. i didnt ask this question for people to bash my cam choice. i know they are better cams out there and they are mixed reviews but im happy with it and i like it. anywho back to heads. i thought the better flow would be better if you add more fuel?please someone explain.

[rich weyand]

At high flow rates (high rpms) you want to keep runner velocity up to build momentum pressure against the closed intake valve so when it opens the mixture gets pushed in, increasing volumetric efficiency and dynamic compression. Too big of runner volume for a given flow rate means the velocity is down and you don't get that push. This only matters at high flow rates, so you probably won't notice a difference potzing around, but you would have higher peak performance on a 350 with smaller runners. When you stroke to 383, you will have enough flow to use the bigger runners and still maintain the optimum velocity.

At least, that's my story, and I'm sticking to it.

[Caleb]

ok that was very helpful. so would it be better if i did like a 200cc for the 350 and i can use it on a 383? i dont want to give up performance and i want to notice the difference.

[rich weyand]

180 cc work well for 327-400 SBC.
200 cc work well for 383-434 SBC.

So the 200s are over size for a 350, and won't come into their own until you stroke it to 383. But 180s will work well on both 350 and 383.

You really want to keep the runner velocity up.