Larry, the out of the box E heads are good to over 500 hp on pretty "mild" 455 applications. Our test engine prepared here last summer made 505hp/551 tq with unported 87cc heads. If you are considering the 72 cc for a 400 street engine they will make over 400 hp with ease on pump fuel. I would consider using better springs, they are delivered with a pretty stiff single spring with dampner. If you are already using a "D" port head KRE is nearly finished with their new aluminum "D" port heads. I've been directly involved with the testing of these heads, they should be available in about 3-4 weeks......Cliff
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https://cliffshighperformance.com/
73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile),
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