Power Down?


A friend of mine has a 1971 440 Magnum engine he is dyno testing. The engine has been bored over 20 thou. and has Keith Black hypereutectic pistons at 9.5 to 1 compression. The engine is using stock components—intake, exhaust, AVS carb with factory jetting, and even an NOS 440 Magnum camshaft. An electronic distributor was used during testing and it was run on premium gas. The engine has no accessories present and the best he could achieve was 330 hp at the crank. Shouldn’t the output be closer to 370 hp? I’m pretty sure I read how Tom Hoover and the other engineers at the Chrysler lab tested these engines and got HP figures that they said were “very good numbers” around 375 horsepower. Have you ever seen any of the dyno test sheets from the lab testing done back then? What are your thoughts on this situation?

The numbers seem about right. 1968‑70 (10:1 compression) 440 HP engines were rated 375 SAE gross HP—that was cold, bare (no water pump, fan, alternator, open exhaust, deep oil pan, etc.). Look at the 1972 specs for some “real” (SAE net) numbers.
Still, be sure there’s correct spark advance—something close to 35° at 3,000 RPM, WOT.
Watch that cam on today’s oils…best to add some ZDDP.

0 0 vote
Article Rating
Notify of
Inline Feedbacks
View all comments

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More

Would love your thoughts, please comment.x