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Steve Hagberg · 06-13-2016, 07:27 PM

I have a copy of a "Stock Engine Test" published by the GM Engineering Staff dated Oct. 17, 1966. The Forward to the report states "As part of the Stock Engine Test Program, a a 1966 Plymouth 426 cubic inch, Hemi-Head, 425 horsepower engine, as used in the Plymouth Belvedere I four door sedan, was tested in the Engineering Staff Test Department at the General Motors Technical Center". This report was an amazingly thorough dyno flog of this engine. The Forward goes on to state that the engine was removed from the car with 29 miles on the odometer, was run for 50 hours to break it in. The combustion chambers were cleaned and the valves lapped, and then it was tested on the dyno. Unfortunately there is no other information on the color, Vin number, or mention of what was done with the car when the test was completed. Interestingly the horsepower numbers were almost exactly the same a what the Engineering Street Hemi Development Report published by Chrysler showed, And it was significantly more than the published 425 Hp. There must have been a four door on a showroom floor that GM bought to satisfy their curiosity.

06-13-2016, 07:27 PM	#23
Steve Hagberg Junior Member Join Date: Dec 2007 Posts: 38 Likes: 0 Liked 0 Times in 0 Posts	Re: 67 4 dr hemi belvedere I have a copy of a "Stock Engine Test" published by the GM Engineering Staff dated Oct. 17, 1966. The Forward to the report states "As part of the Stock Engine Test Program, a a 1966 Plymouth 426 cubic inch, Hemi-Head, 425 horsepower engine, as used in the Plymouth Belvedere I four door sedan, was tested in the Engineering Staff Test Department at the General Motors Technical Center". This report was an amazingly thorough dyno flog of this engine. The Forward goes on to state that the engine was removed from the car with 29 miles on the odometer, was run for 50 hours to break it in. The combustion chambers were cleaned and the valves lapped, and then it was tested on the dyno. Unfortunately there is no other information on the color, Vin number, or mention of what was done with the car when the test was completed. Interestingly the horsepower numbers were almost exactly the same a what the Engineering Street Hemi Development Report published by Chrysler showed, And it was significantly more than the published 425 Hp. There must have been a four door on a showroom floor that GM bought to satisfy their curiosity.