Know your engine.
We know your headers.
Three clicks from engine combination to the exact Thorley header SKU sitting on the shelf in Canton — with the dyno-proven torque-gain range printed right on the product card. No guesswork. No "fits most."
- 1,860+ SKUs in stock, 1964–2024 applications
- Mandrel-bent in Ohio, shipped same-day before 2pm ET
- Lifetime no-rust-through warranty, honored since 1982
Tell us what's under the hood.
Pick year, make, model, and engine. The finder returns only the Thorley SKUs we have actually built and dyno-tested for that combination — including the part number, primary tube diameter, collector size, and torque-gain range from independent Engine Builder Magazine testing.
- Stock or modified? The selector accepts engine codes, displacement, and any cylinder head casting you've installed.
- Auto or stick? Transmission matters for clearance — we factor it in.
- Not street-driven? Strip the emissions filter and the SKU list grows.
Six platforms we build more of than anyone.
If you already know the engine family, jump straight to that catalog — the four top sellers below account for 71% of weekly orders. LS/LT and Big Block Chevy hold the dyno records in our test cell.
Don't see your engine? The selector above covers 1,860+ applications including Pontiac, Oldsmobile, Buick, AMC, and the W-series Big Block Mopar wedge. Run the finder →
Three answers in, one matched header set out — with the torque-gain range proven on the dyno.
Every SKU the finder returns comes back with the engineering data a builder actually needs before they click "Add to Cart." We don't make up numbers in the marketing department. We put them on the bench at 4,800 RPM and print what the dyno says.
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SKU resolution, not a recommendation engine.
The finder pulls from a catalog of 1,860+ part numbers mapped to specific engine codes, head castings, transmission types, and emissions categories. If a combination isn't in the catalog, it returns nothing — we won't sell you a header that doesn't fit.
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Hardware, gaskets, and fasteners included.
Every matched SKU ships with the bolts, gaskets, and reducer cones listed on the product page — no last-minute trip to the parts store. Collector gaskets are die-cut in-house; hardware is grade 8, not the import stuff.
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Dyno-tested torque range, printed on the card.
Each product page lists the torque-gain range from independent Engine Builder Magazine dyno testing (March 2019 issue). Numbers are ranges, not single claims, because gains vary by engine combo, tune, and altitude — and we tell you that upfront.
Fitment data you can actually trust.
Every Thorley SKU is documented, dyno-tested, and backed by a human on the phone — not a chatbot. Here is what's behind the catalog.
- ISO 9001:2015Certified since 2009
- 412,000+Header sets shipped
- 47American craftsmen
- 99.2%On-time delivery, 5-yr avg.
- SEMA 2016Best New Engine Performance
Six ASE-certified techs answer in under 38 seconds.
If the finder comes back empty — or you have a stroker, an aftermarket head, an oddball truck engine, or a one-off race combo — pick up the phone. Our fitment hotline runs Monday through Saturday, 7am to 7pm ET, with no phone tree and no offshore call center.
- Speak to a tech who has actually installed a header set, not a script reader.
- We can spec a custom build around your combination — 1,860+ SKUs is the standard library, but 47 craftsmen in Canton can hand-port a one-off.
- Same-day shipping on 94% of orders placed before 2pm ET.