How does acid porting add air flow to cylinder heads and intake manifolds?

Acid porting is the enlargment 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. In a couple of very important ways, “Acid Porting” is a different procedure than our “UnderCover Porting”.

First, the intake port can be made larger with "Acid Porting". Remember that “UnderCover Porting” is the hand grinding of critical areas of the head where the port floor meets the valve job, which increases the port size 3 to 5 cc’s. With “Acid Porting” we can open the port 8 to 13 cc’s.

Second, “Acid Porting” will keep the entire port looking more stock. This is especially vital during inspecton of the first couple inches of the intake ports around the pushrod area.

When “Acid Porting” alone is done to the intake port, the air flow will be similar with “UnderCover Porting”, but the port will be larger. Our theory is to keep the port as small as possible while achieving maximum air flow. Therefore, in most cases, we recommend “UnderCover Porting” be performed first. At that point, 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 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.

Call us today to ask how porting cylinder heads and using acid ported intake manifolds can make your car go faster!