I’ve thought about headers off and on for about 5 years. After 20 years of use one of the OEM manifolds developed a crack so I decided to take the plunge. I don’t care much for the shorty headers that bolt in place of manifolds. For a compromise between fit and function I decided on a set of mid-length headers. I have a well-respected header design program called Pipemax. For a 5.7L engine making 300 hp at 4,800 rpm (my goal) it recommends 1.275” -1.4” I.D. primaries and a 2.5” OD collector. The big name offerings used 1-5/8” diameter 18 gauge tube which is both oversized and a little light for truck use. Some of them also have a poorly shaped 3” diameter collector. I came across L&L Products that manufactures their own line of headers in-house in Texas. They offer a header with 1-1/2” diameter 14 gauge (0.090" wall) primary tubes (1.320” I.D.) a 2-1/2” merge collector ½” thick flanges and a high temp nickel coating inside and out. The flange opening is about the same size and shape as a stock SBC exhaust port unlike many of the big name headers with a huge flange opening to accommodate big aftermarket performance heads.
Bolting the headers on was pretty straight forward. L&L forgot to send the flange gaskets so I used a set of FelPro 1404s I had kicking around. I ended up deleting the alternator/power steering support bracket on the driver’s side for now. I’m looking at a way to modify and reinstall down the road when I do the engine swap. There is no provision for the hot air tube on the passenger side, which I’ll address before it gets cold. The headers arrived with a set of connecting pipes for twin cat vortec engines. I would have used them, but they were only 2” diameter. Instead, I purchased some 2.5” mandrel bends from Summit an O2 sensor bung and a new Walker cat, and a 2-2.5” into 1-3” merge collector from Cone Engineering to build a custom Y-pipe.
I drove over to my dad’s with the open headers and connecting pipes installed. I had disconnected the O2 sensor and despite getting up to operating temp for several minutes the ECM never through a code. It took dad and I about 4 hours to fab up and install the Y-pipe. I’m pretty pleased with how it came out.
With the headers installed the exhaust note is unchanged at idle and low cruising speeds. I don’t notice any header noise in the cab, probably due to the thickness of the tubes. It has a little deeper rumple when I lean into the throttle, which I like. The rest of the system is 3” single with the longest 7” diameter see-through Magnaflow muffler I could find. I’ve only driven around town so far so I can’t say if it makes any more power. Keep in mind right now I’m running a bone stock 165K mile L05.
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Originally Posted by Roadknee
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