Undercover Porting

 What is “UnderCover Porting”?                                                                                      Brzezinski Racing Products developed “UnderCover Porting” back in the 1980’s when racers wanted more power but needed the ports to look stock. The goal of “Undercover Porting” is to improve airflow as much as possible while keeping the ports as stock appearing as possible. To achieve this goal, we perform flow bench research and development work on each type of cylinder head.

“UnderCover Ported” RHS Vortec Head The Vortec style chamber is superior to standard Chevy

“Undercover Ported” Vortec head. Even with the valves removed, it resembles a stock head.

“UnderCover Ported” heads do not have the area below the valves blended and polished. Depending on the style of head, we may do some limited work in the “Bowl Area”. We can gain air flow with more extensive porting to this area, but it isn’t worth the risk of having the port  more visually modified. In essence, we only rework the areas that will improve air flow and can be effectively “covered-up”. Our SST Ported & CNC Sportsman Ported heads have these areas extensively reworked.

Picture of part

“UnderCover Porting” includes intake port modifications, chamber work, exhaust port reworking, cover-up work, valve guide sizing and the final machining of the valve seats. The end result is a head that will produce a measurable improvement and look as stock as possible.

How much does “UnderCover Porting” help?

The heads required for many racing applications such as Vortec, Dart SS, Engine Quest 350I, Engine Quest Vortec, Double Hump and Open chamber heads were designed for street applications, or as street replacement heads, where the engine doesn’t see much over 4,000 rpm.  In a typical racing application, your engine will not be running under 4,000 rpm.  The difference from a stock set of heads to “UnderCover Ported” is huge, especially if the engine is running over 6,000 rpm.  The stock heads were just not designed to run this type of rpm.

Over the years, we have found that “UnderCover Ported” heads consistently produce 15 to 20 more horsepower than stock heads.  Sometimes this improvement is more in the 25 to 30 horsepower range, especially on heads that were designed for street use that are run on race cars.

  On the set of dyno tests to the right, we took a 355 with a set of stock ‘492 double hump head vs. a set of “UnderCover Ported” ‘492 heads.  The valve size and chamber size were the same on both sets. All we did was swap the heads, which took less than an hour.  We picked up 27 horsepower at 6,000 rpm with the “Undercover Ported” heads. Then, just for fun, we replaced the stock 2 barrel intake manifold with our Stage 1 ported intake; with this change over 20 more horsepower was gained!  The test engine was a 355, flat top, 10.5 to 1, with a 500 2 bbl carb and headers. h06_acidUCdyno_000_000


How much is this “UnderCover Porting”?  Can I have my heads ported?

You might be wondering if we can do “UnderCover Porting” to your heads?  Yes, we can perform our “UnderCover Porting”,  or any of our other procedures,  to your new our used heads.  Depending on the condition and type of cylinder head, “UnderCover Porting” to 1 bare pair of small-block Chevy casting runs from $795.00 to $1,200.00.  This is labor only to new or used castings.  “UnderCover Porting” modifications include our CNC machining, intake port modifications, combustion chamber work, exhaust port modifications, cover-up work, valve guide sizing and / or replacement and a flow bench developed valve job. The end result is a head that will produce a measurable performance improvement and look as stock as possible


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