What are Tri-Y headers and how do they work?
We frequently get calls asking us to explain the theories behind the Tri-Y headers, but it just can't be done properly over the phone. To make things easier, this information will give you a basic idea of the key elements of Tri-Y design theory.
You've just connected, or paired, the cylinders that fire 180 distributor degrees apart from one another. Check this out on a distributor and you'll see that #1 is directly across from #6, #8 is directly across from #5, and so on. If you could pair your header tubes like this, you would have theoretically ideal headers. One pair of cylinders would fire every 180 degrees of distributor rotation. The high-pressure pulses from each paired set of tubes would be allowed one complete crankshaft revolution's worth of time to smooth out before its partner cylinder fired. The pulses would be organized so they could proceed out the tailpipe in an orderly fashion.
If we blend the gases from #1 with those from #5, and blend the gases from #3 with #7, we get the paired cylinders much closer to being 180 degrees opposite one another than if we just dumped all the exhaust gases together and let them fight their way out of the collector as a four-tube header does. Now check out the driver's side on the left.
That's all there is to it. Relatively simple, very effective and applicable to V6, straight 6 and 4cyl engines as well.
Mainly because they're very labor intensive to manufacture and most companies are looking to produce a cheap header over a true performance header. This is also why Thorley takes the time to make every header they produce, 50-state SMOG legal. Each header comes with CARB certification papers and sticker. Very few headers on the market do this which makes their headers illegal in most places.
Header construction. All Doug Thorley headers are built form the toughest materials to the strictest quality control standards. 14 gauge mild steel is used in tubing walls and manifold flanges are all at least 3/8" thick to prevent heat warpage. All headers also come with a nickel-chrome finish. Your header will have a shiny chrome finish at installation and Thorley's rust protection ensures it will look like a million bucks longer than your vehicle's body will last.
The Doug Thorley Cat-Back Exhaust System juices-up your Jeep with free-flowing power. It utilizes custom CNC mandrel-bent 16-gauge aluminized steel tubing to eliminate restrictions and backpressure. The mandrel bending provides a full diameter tube thru all bend so there are no choke-points in the system... unline the factory exhaust which has a bunch of bend that squish the tube diameter way down.
< File image, your kit may vary.
Bolts directly to stock mounting positions at the catalytic converter without any modifications required. Doug Thorley Exhaust Systems employ factory-style hangers for straightforward mounting. Exit pipes are capped-off by a great looking chrome exhaust tip.
The system also includes a high-performance Thorley muffler. Your Doug Thorley Cat-back Exhaust carries a Lifetime Warranty for the original owner!
Your Jeep came with ample horsepower and torque for the average grocery-getter driver. Doug Thorley Exhausts have never been much for average, though. Thorley's decades-long mission has been to make stock exhausts look inferior. This is where Doug Thorley Exhausts come in for your Jeep. Using 16-gauge aluminized steel tubing, custom CNC mandrel bending, and a free-flowing muffler, a Thorley Exhaust adds instant punch at the pedal. It provides loads of low-end pulling torque, too.
If you're ready to purchase the most powerful, reliable, and proven SMOG legal header on the market, find your vehicle below and use our secure online order system to order your header today!
All Cat-Back, and some Thorley header kits may drop-ship direct from Thorley (Summit Industries)!
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The Thorley 634Y is used in all 6 cyl Jeep applications.