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Range Of Rpm On 454ci

Old 01-13-2004, 08:38 AM
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Default Range Of Rpm On 454ci

Hopefully you guys can help me out here. I was wondering I have a 31' 1979 Excalibur t-454 400hp motors trs drives 23p mirage 3-blade. does anybody know what the RPM range should be for these motors? right now the most I can get out of them is about 4700rpm ??
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Old 01-13-2004, 08:51 AM
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If they are 400 MCM Cyclone engines then 4800-5200 was the recommended RPM
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Old 01-13-2004, 08:53 AM
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I would shoot for 5000 to 5200 as long as the engines are healthy. Primary concern being valvetrain.

Dave
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Old 01-13-2004, 09:28 AM
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these are the original engines in that were in the boat about 800hrs boat sat in a garage for about 10 years
comletely stock never rebuilt. still sound great.
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Old 01-13-2004, 09:40 AM
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Most likely the rpm is down due to weak valve springs, they will make a very effective rev limiter I`m sure the valves aren`t sealing too well either.


800 hrs, they have had a good life. Time for good old 'look see'
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Old 01-13-2004, 09:54 AM
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And weak valve springs spells disaster at elevated rpms. Valves won't get enough seat time to cool properly. A valve job with a checking of the springs is minimun to avoid disaster. Also will give a nice chance to service the exhaust system.

Dave

Last edited by blue thunder; 01-13-2004 at 10:00 AM.
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