How does acid porting add air flow to cylinder heads and intake manifolds?
Acid porting is the enlargement of the entire intake port using chemical treatments. After “Acid Porting” the port looks very much like stock with the original casting lines and markings in place. “Acid Porting” is a different procedure than our “Undercover Porting“.
In most cases we recommend “Undercover Porting” be performed before acid porting. If the engine combination calls for more intake port volume, we recommend the addition of “Acid Porting”.
Each head we have ever tested can be improved with our “Undercover Porting“. The flow improvement and procedure varies depending on the type of head. Some heads like the production Chevrolet castings improve substantially at valve lifts as low as .300″ lift with “Undercover Porting”. Other heads like the 200 cc and larger Dart Iron Eagle do not show measurable improvement until just after .500” lift.
While all heads can be improved with “Undercover Porting“, some heads do not need acid work; only the heads that are too small for a racing application like the Chevrolet ‘492, 305 heads, Vortec and some of the after-market heads that are required like the EQ and Dart SS heads. These are mostly production heads run in a race application. Thus, the need for more intake port volume. All of the Chevrolet heads were originally designed for street use where the engine never sees over 3,500 rpm. However, on a race motor the engine is never under 3,500 rpm. Because the intake ports are so restrictive, for racing at anything above 5,000 rpm the ports need to be made larger for maximum performance.