Thorley Header

Nov. 01, 2005 By ORC STAFF

Doug Thorley Header kit. Click for a larger image!No good Samurai should do without a proper header. The improvement in the engine's ability to breathe makes a difference in overall power output, and these little engines can use all the help they can get.

Doug Thorley Headers of Corona, California makes a fully smog legal (the only one to be so certified of which I am aware) header for the Samurai 1.3L engine (Part #700Y). It can also be used by those that have replaced their block with an 8-valve Sidekick or Tracker 1.6L engine and used the Samurai head. The header has both the manifold tube and the air intake pre-heat hose fitting, which some headers lack.

I had my header installed by Petroworks Off-Road Products during the course of my spring-over-axle conversion. The smog legal aspect was my main decision point in the purchase of this header. (California smog checks are best dealt with in advance.) The fact that the Thorley had what appeared to be the heaviest gauge tubing and the best workmanship was a bonus.

Installation is straight-forward, with the only "tricky" point being the test fitting of the collector-to-exhaust pipe adapter to ensure it will properly mate up with the short piece of pipe that serves as the catalytic converter's input. Once everything is lined up, the adapter must be welded to the cat input pipe to meet California emissions requirements.

If you read and follow the instructions provided by Thorley with the header, you should have no problem with this unit. The only "follow-up" to installation is post installation bolt-tightening; important in preventing leaks. Thorley's instructions provide what has so far been an effective procedure for maintaining fasteners at the proper torque specs.

Collector detail.The improvement in responsiveness of the Samurai's engine was noticeable. The header gasket and collector gasket have never leaked, although there is a rather distinct odor of "cooking in" gasket for a while after installation. The header's chrome finish is a high nickel content plate that is designed to protect the metal, not provide for a cool "go-faster" appearance. It does change colors over time; mine has aged to a rather interesting deep metallic blue shade in some areas, and an amber metallic color in others. There is some minor rust evident on the collector adapter and bolts now that they've been exposed to winter weather, although the remainder of the header is rust free.

--Scott Gomez Newsletter
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