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Chrysler 400 B-series - Hemi Power At Half The Cost

The stealthy 400

Chrysler 400 - Hands On

We should probably clarify this article's headline right away. By hemi power, we mean factory-rated horsepower for something like a '68 Hemi Roadrunner, and by half the cost, well, that's self-explanatory. The relatively low cost is why this build is running in this issue. Brian Hafliger of IMM Engine and Dyno was able to take a lowly Chrysler 400 block and piece it together with a clever combination of used factory parts, some good machining, and a mild aftermarket cam kit, and make as much factory-rated horsepower as the mighty Dodge and Plymouth 426 Hemi engines in '66 through '71 Dodge and Plymouth cars. Best of all, aside from the machining, this Chrysler 400 engine can be built at home. There were no exotic Hemi parts in this engine, and no black-magic porting was done to the cylinder heads or intake manifold. Mopar fans, start scrounging eBay or your local swap meets and salvage yards. Grab yourselves a Chrysler 400, and make some Hemi power.

Chrysler 400 Hemi On the Dyno

We were honestly surprised by the power this combination made. None of the random guesses from the peanut gallery crowding around IMM's dyno cell were this high. Brian and his dad were hoping for about 415 hp, but everyone else guessed lower than that. All eyes widened as the horsepower figures crested 415 on the very first pull. After just minor tweaking to the carburetor jetting and advancing the timing by 2 degrees, we achieved a peak horsepower number of 426.7 at 5,700 rpm, the same as what the 426 Hemi in Roadrunners and Chargers were rated at. There may actually be a few more ponies lurking inside this engine, but Brian didn't feel comfortable pushing the engine too much farther. The weak links in this combination are the OE-style rocker arms, which weren't designed for the spring pressures and engine speed we were asking of them. If you are looking to replicate this build but have a little more money to spend, consider a rocker-arm upgrade. Otherwise, this is an engine you could drop into a classic Mopar and surprise a few people with the power you're getting from what was never really considered to be a performance engine.

*Note: These are IMM's prices. Your local machine shop's costs will vary.

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