Will a Mummert manifold and the best car headers add any performance to a stock 312? Motor has ecz-g heads, 1.54  rockers, the better exhaust manifolds, Holley 4150. Not sure on bore size, or cam specs but assume cam is stock.  If I can buy 25 HP and some torque it would be worth it, for 10 HP probably not.  Any thoughts appreciated, I've been thru the Eaton test pages (amazing) but none really test an otherwise stock engine so I'd be blind guessing any value.  Thanks

Ted, Redding, CA

I'm thinking about doing both manifold and exhaust. I just ordered MSD 8383 kit, also the original style wire routing clamps, want to be done with the points.  I have an Offenhauser with 3 94s (I Know, don't say it), but I'm not ready for it. The Holley is 600 CFM and I'll keep it if it stops leaking and will work.  Need to get stuff coming and 25 HP will make me spend, Not going to race anything so would be satisfied at anything over 275, figuring it's good for 240 now when tuned correctly.  That's good news thanks. 

Ted, Redding, CA