Below Swim Platform Low Port Exit Jacketed System - S/B Chevy 350

Below Swim Platform Low Port Exit Jacketed System - S/B Chevy 350 

Below Swim Platform Low Port Exit Jacketed System - S/B Chevy 350 Low Port Header 31" Wide

These headers are designed to be a replacement for Mercury, OMC or jet manifolds when the exhaust ports are mounted low in the boat. For example, under the swim step or when elbows are used with the stock manifolds. Headers will have about 1/2" clearance between header and tall Moroso valve covers. Headers come complete with bolts, gaskets, water fittings, pet cocks, 4" elbows for bottom, etc. (less 4" hose and 4" hose clamps). Factory oil filter requires relocation.

When comparing performance exhaust systems it's good to understand the different systems on the market today and the performance demands of your engine. Understanding how a header works will help you decide on which exhaust system is best suited for your application.

Headers have two basic functions. First is to simply relieve back pressure. For example, when looking at a manifold you see a 4" diameter exhaust hose, but the actual exhaust gas opening is about 2-1/2" diameter. Most performance manifolds and some header manufacturers use a 4" exhaust hose and 3" or 3-1/2" OD exhaust gas tube. All of these headers use a 4" OD exhaust gas tube and a 5" water jacket tube until the water gets introduced into the exhaust gas stream, then it gets reduced from 5" to its 4" exhaust hose diameter. At no time does the exhaust gases see a diameter smaller than 4" OD. When looking at these exhaust gas openings consider their area not their diameter. For example, a 4" OD opening has an area of approximately 12.56 sq. in. A 3-1/2" opening has an area of approximately 9.62 sq. in. That is 25% smaller! A 3" opening is approximately 7.06 sq. in. and a 2-1/2" opening is approximately 4.90 sq. in. which is 60% smaller.

Performance figures on headers vary considerably. As a rule, the higher horsepower engines benefit more than the lower horsepower engines. For example, the 330 hp Mercury engine will gain approximately 50 to 75 rpm, where as the 365 hp Mercury engine will gain approximately 300 to 400 rpm (45 hp). Blown engines gain up to 800 rpm (80 hp). Of course this is comparing these headers against stock Mercury center rise manifolds.

Our Magnum header starts with Mandrel bent 316L stainless steel interior tubes. The exterior tubes are Mandrel bent heavy wall steel tube (.074). The tubes are then mechanically etched by sand blasting and then assembled. Finally, a corrosion resistant silicone ceramic coating is applied to the interior of the header while the exterior receives a powder coat finish.


Through continuing research Lightning Mfg. has developed a Dual Porcelain Coating that resists the harshest of salt water environments. Now as an option they are able to apply the same high tech coating to a 316L stainless steel lined header once thought to be the cracking alloy and render it crack resistant.

MSRP: $3,200.00
Your Price: $3,099.99
You Save: 3% off MSRP!

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