Tech:Engine/K Series/Exhaust

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There are several different types of stock exhaust manifold:

  • Single plane, single outlet
  • Dual plane, dual outlet
  • Single plane, single outlet, -C emissions

The single plane manifold is usually fitted to KE1x and 2x from the factory, it is restrictive and should be the first thing removed when upgrading the exhaust. The dual plane manifold is quite good, it separates opposing cylinders and joins them under the passenger footwell. This comes factory on most KE3x cars. You may leave this as it is, unless you're hunting for big power. It won't fit on a KE2x, as it hits the steering idler arm, however this could be remedied with custom dual pipes. They're just mild steel. The last type of exhaust manifold is just stupid, it joins the exhaust flow back into the inlet manifold via a vacuum-actuated thing. Get rid of that!

All stock exhaust manifolds connect with the intake manifolds at a bolt triangle. This triangle differs in direction /\ or \/ depending on the year of the car, it seems KE1x only had the "other" way compared to all other models. The purpose of this is to heat up the intake manifold so the fuel atomises better (in theory) and car warms up sooner.

Of course, nothing beats a good set of tuned length extractors. These range in price from free to AU$250 new, with the average for second hand units being AU$50-$100. Some extractor systems have an extension to the stock manifold triangle, most don't. Having the inlet manifold not connected to the exhaust manifold will mean you'll need to add another 5 or so minutes onto your warm-up time.

Pipe size

Don't go any bigger than 2", nuff said. There is really no need to go mandrel bent, but if you can afford it or do it yourself, why not? It is said a mandrel bent pipe is equivalent to a press bent pipe quarter of an inch less in size. (ie: 2" press = 1.75" mandrel)


Haven't really done alot of research on this one. My KE35 had a resonator and a "turbo" style muffler and it wasn't too noisy. Stewart's KE15 has two resonators and a reverse flow muffler, it is about the same volume, but that's the motor :) My KE25 has a small resonator and some sort of huge can and a 4" droop tip, it sounds very angry, nobody believed it was a stock 3K, now with the 4K I clutch in whenever I see a cop car.

The more you work a K motor, the deeper and angrier they seem to get. I don't know why it is, but these are really nice sounding motors. If your cam is too big, the motor will sound like a bridgeport rotary, seriously!

Article by Superjamie

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