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Acid Porting
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Home : Cylinder Heads : Undercover & CNC Porting : Acid Porting
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Acid porting is the enlargment of the entire intake port using a combination of chemical treatments. The advantage of “Acid Porting” is that the port looks very much like stock with all of the original casting lines and markings in place. No hand porting is performed with this procedure. In a couple of very important ways, “Acid Porting” is a totally different procedure than “UnderCover Porting”. First, the intake port can be made larger via "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. By “Acid Porting” we can safely open the port 8 to 12 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.
NOTE: We perform “Acid Porting” to the intake ports only.
If “Acid Porting” alone is done to the intake port, the air flow will be about the same as 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”.
| Part # |
Description |
Price |
| 434XXXX |
“Acid Port” 1 pair of SBC heads. |
$695.00 |
| 434YYYY. |
“Acid Port” 1 pair of non-SBC heads. |
895.00 |
3 ways “UnderCover Porting” or “Acid Porting” will make your car go faster |
| FIRST |
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. |
| SECOND |
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 Bow Tie. These are mostly production heads run in a race application, thus the need for more intake port volume. All of the Chevrolet heads - except for the Bow Tie - 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. |
| THIRD |
All production cast iron heads suffer from “core shift”. Even with the newer style 200 cc and larger heads, measurable improvements are achieved with port modifications. |
While the larger after-market heads like the Dart Iron Eagle, World Products and Iron Lightening heads do not need acid work because the port is already large enough, by performing “UnderCover Porting” we can improve the air flow 10 to 25 cfm. If you must run a particular size head, consider going with a larger size and, perhaps, changing the casting numbers. |
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