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The Quad 4 was a 4-cylinder, 2.3 liter engine GM designed in the late 80's and produced 180-190 hp depending on the level of tune. Impressive numbers on paper when the 5.7 liter V8 engine in the Camaro was barely making 200 hp.

However the reliability problems (head gasket failures, etc) were pretty common for this motor and gave it a bad reputation.

Was it a fundamentally flawed design? Or did GM corner-cut in places that they shouldn't have? Can these motors be made reliable with readily available aftermarket parts?

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  • I'd also ask Ishtar the engine has a poor reputation. What actually fails and can it be built to be reliable (as opposed to modified)?
    – dlu
    Jul 27, 2016 at 13:31
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    @dlu who's Ishtar?
    – Zaid
    Jul 27, 2016 at 16:43
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    I have no idea. Autocorrect is not my friend. Meant to say "ask if the engine". As in bad design vs. bad production or quality control.
    – dlu
    Jul 27, 2016 at 17:02

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I don't see it as a "fundementaly flawed" design at all. One of the first mass-production DOHC 4-bangers, and over about 6 years they only made about a quad-drillion of them.

The early ones were buzzy and shook themselves apart, but later versions added balance shafts. I'm not aware of head gasket failures or other problems beyond what you'd expect for any mass-produced engine.

The demise of the Quad-4, in my opinion, is only due to replacement with the Ecotech, and the newer GDI versions are incredible in their own right.

I am NOT a GM engine fan, but the Iron Duke, the Quad-4, and the Ecotech all represent significant engineering triumphs in their era. (Being a Subaru fan, I have to lean towards the EJ series flat fours with both OHC and DOHC varients, with equal or better volumetric efficiency as a Quad-4, and coming on the scene almost a decade earlier.)

The W41 is still sought after and commands high prices, and there's a subculture of hotrodders who feel the Quad-4 is a modern "Offy", even if it's only the appearance.

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  • I owned an iron duke. It was a sub-100HP dog. Newer, better technology engines had already been introduced. Virtually all iron dukes died sub-100K miles due to the "phenolic resin composite" timing gear. All Fiero versions were recalled for engine fires. Fortunately they were not interference engines and could be fixed. But in all respects, reliability, fuel economy, power to weight ratio, redline, and performance, they were dogs. It was no engineering triumph because it excelled at nothing, beyond being a better engine than the Vega engine- a very, very, very low bar, indeed.
    – kmarsh
    Jul 28, 2016 at 3:33
  • Agreed to some extent, but Fiero engine fires were no fault of the Iron Duke. And while not the cherry of the 3, the Quad-4 was GM's answer to the Iron Duke. Phenolic gear aside, no Iron Duke died. They were impossible to break. And with a 16 year run, blame pre-Bob Lutz GM for the shortcomings, not the engine.
    – SteveRacer
    Jul 28, 2016 at 3:38
  • Died, requiring a tow, while driving along a superhighway bridge with no shoulder, exposing me and others to danger, is died. Yes, it was repairable. It still died and could not be restarted.
    – kmarsh
    Jul 28, 2016 at 17:12
  • The later versions with balance shafts made a lot less power - 150 hp compared to 180/190. That's why i'm speculating that the early ones were "pushed too hard" and without the necessary margins of safety.
    – masospaghetti
    Aug 3, 2016 at 19:44

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