LS swap headers and exhaust: choosing by chassis

How we put this guide together

156 of the 2,012 LS swap questions we pulled from forum threads were about headers, manifolds or the exhaust behind them. Almost none were about horsepower. They were about fit: will LS1 headers fit my truck?, why does the driver side hit the steering shaft?, which header clears a 4L80E? The short answer to all of them is that a swap header belongs to a chassis and an engine position, not to the engine. Here's how we choose one, what has to clear, and how to size the rest of the exhaust.

Step 1: Pick the type that fits your build

Type	What it's good at	What it costs you
Factory manifolds (truck, F-body, Corvette, 5th-gen Camaro)	Cheap or free, quiet, no leaks, often fit tight chassis	Least flow; the right one depends on the chassis (truck manifolds fit some trucks and hit the frame in others)
Cast swap manifolds (Hooker BlackHeart 8501/8502 series, Speedway V-band manifolds)	Tight-tuck shape made for swaps, leak-free, keep the starter and plugs reachable	Less peak power than tube headers; Hooker rates the 8501HKR to about 500 hp
Shorty / block-hugger headers	Fit bays where long tubes can't (S10, Ranger, E30, Toyota pickup), better flow than most stock manifolds	Short, unequal primaries; almost always less power than long tubes
Mid-length headers	The usual compromise in C10s and A/G-bodies: collector ends ahead of the transmission, more ground clearance	Some still need bellhousing trimming on big automatics
Long tubes	Most power, best scavenging	Need room for primaries and collectors under the floor; most are chassis- and mount-specific; many are sold for off-road use only
Turbo manifolds / ram-horns	Turbo builds; put the turbo where the chassis has room	A whole different exhaust and tune; not for an NA build

On a stock 5.3 or LS1, headers alone are worth roughly 5 to 20 hp. They pay off as part of a combination with a cam and a tune. If the budget is tight, a set of manifolds that fits beats a set of long tubes that needs the steering re-engineered. More: long tubes vs shorties.

Primary size: 1-5/8 in suits stock and mild engines, 1-3/4 in is the common street size, 1-7/8 in is for big-cam and 6.2/LS3-class engines. A bigger primary on a small, low-rpm engine costs torque down low; one E46 builder who tried 1-7/8 in found it harder to fit and saw no extra power. Collector: 3 in is the usual size on long tubes and mid-lengths, 2-1/2 in on most shorties and cast manifolds. Check that the collector matches the pipe you plan to run.

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Step 2: Let the chassis and mounts decide

Swap headers are bent around one chassis's frame, steering and floor, and one engine position. That's why the same LS1 header that fits a Camaro won't fit a C10, even though the bolt pattern at the head is identical across LS engines. Work through it in this order:

1. Your mount position. Pick the mounts first; the header has to match them. Hooker, Sikky, Vorshlag, CX Racing, ISR and Novak all draw their headers around their own mounts. More: engine mounts and swap kits.
2. Steering shaft and box. The driver-side primaries and the steering shaft are the tightest spot on most swaps. Some headers route a primary around the shaft (S10), some kits move the engine sideways (CX on the E46), some need a new shaft (Fox Mustang with aftermarket K-members, E46 with Sikky). Right-hand-drive cars are often not covered at all. More: steering shaft and box clearance.
3. Frame and crossmember. Truck manifolds on a squarebody with the engine 3 in forward land on the driver frame rail. Caprice manifolds in a Tacoma point straight at the crossmember.
4. Transmission. 4L80E, TH350 and TH400 bellhousing ears often need trimming for long tubes and mid-lengths. Novak's XJ headers don't fit a 4L80E at all. Jags That Run RX-7 headers won't fit a 4L60E.
5. Starter, oil filter and clutch line. Check that the starter can come out without pulling a header (some E46 headers only fit the OEM starter, not a mini), that you can reach the oil filter, and that the clutch master line clears (E9x needs a braided line rerouted).
6. Floor, column shift and plug wires. Long tubes can need floor clearancing (ISR on the 240SX), column-shift linkage often has to become a cable kit in C10s and A-bodies, and tight headers need angled plug boots (Taylor 79013 on Sikky sets, Speed Engineering's own wires on theirs).
7. Oil pan. Some header packages are drawn with a specific pan in place (Hooker's 3rd-gen F-body system with the Holley 302-2, BRP's G-body headers around the LH8 pan). More: oil pan guide.

Step 3: O2 sensors, emissions and the tune

Where the O2 sensors go. The front (upstream) sensors read each bank. With long tubes the collector ends far back, so the bungs usually sit in the collector or just after it. Keep each sensor at least 10° above horizontal (wire end up) so condensation can't run into it, ideally 18 in or more downstream of the exhaust port, and away from the collector merge where one or two cylinders dominate the reading. A wideband for tuning goes in the same way, on the bank you log.

Emissions equipment stays on a street car. If your vehicle came with catalytic converters and rear (downstream) O2 sensors, plan the exhaust so they stay: cats after the collectors, rear sensors after the cats. Several swap Y-pipes are made with cats built in (Kooks 37103200 for the Jeep JK, for example). Many long-tube and swap headers are sold for off-road use only and carry no CARB EO; check your state's rules before you buy. Our tunes never turn emissions monitoring off. More: do I need a tune after long tube headers?

The tune. Headers change how the engine breathes, so the stock fuel and spark tables no longer match. The engine will run, but plan on a tune, and install headers and exhaust together so you only tune once. Start with the turn-on tune builder for a safe first-start file, then finish on a dyno. Rather have us do it? We can build the file from your read or check the tune you have: Tune Report and Start-up File.

Step 4: Size the exhaust for your power

A good starting rule is about 1 in of total pipe diameter per 100 hp:

Power at the crank	Total pipe diameter	What people usually run
About 300 hp (stock 4.8/5.3, LM7)	3 in	Single 3 in
About 400 hp (cammed 5.3/6.0, LS1, LS3)	4 in	Dual 2-1/4 in, or a single 3-1/2 in
About 500 hp	5 in	Dual 2-1/2 in
About 600 hp and up	6 in	Dual 3 in

So a 3 in Y-pipe is about right for a stock to mild 4.8 or 5.3, and a 500 hp engine wants about 5 in total, such as dual 2-1/2 in. Bigger than this doesn't add power on a street engine; it adds drone and cost. An X- or H-pipe behind the collectors helps on duals. Leave room for the cats, and check the pipe routing over the crossmember: some swap crossmembers are made with exhaust passages (Hooker's high-arch SN95 crossmember, Pro LSX's C10 crossmember that tucks 3 in pipes inside the rails), and some X-pipe kits need an aftermarket crossmember.

Common mistakes

• Buying "LS1 headers" for a chassis they weren't made for. Same bolt pattern, different car.
• Mixing a header brand with another brand's mounts. Expect cutting, denting or a different steering shaft.
• Long tubes on a lowered car without checking the collectors. The collector can become the lowest point of the car.
• Pulling the cats to make room. Re-route instead. On a street car the cats and rear sensors stay.
• Leaving the plug wires for last. Stock boots melt on tight headers. Buy the angled wires with the headers.

Find your vehicle in the table below for the headers and manifolds known to fit, and what they need around them.