CHRIS CRAFT COMMANDER FORUM ® .......A photo-intensive technical reference file and ongoing newsletter regarding the original fiberglass Chris-Craft Commander series. This is an independent not-for-profit and non-commercial web site, not affiliated with the Chris Craft Commander Club ~~ or ~~ Chris-Craft Corporation. Our mission here is to "have fun and share information" about the Commander series (and those associated fiberglass boats on the Chris-Craft family tree) for your individual personal use, and by doing so help promote the good name of Chris-Craft, and help preserve, restore, and appreciate Chris-Craft boats. The main reference feature is the ever expanding MASTER INDEX File which contains what we believe to be the world's largest collection of documentation photos and technical information on the Chris-Craft Commander line of boats, (like these original brochure scans, featuring the iconic first 38 Commander styled by Fred Hudson, and many of the great Dick Avery renditions that followed) , (a huge collection of Chris-Craft 427 tuning and specification information), and a few words about how to use the forum.

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Mythbuster

April 23 2012 at 9:45 AM
Paul  (no login)


Response to Re: Bear Z Girl Has sold

Going from "tens of thousands of hours" to something that needs serious attention at 700 hours is quite a tradeoff for the the luxury of speed.

I suppose "any" engine gas or diesel will have the same peril when you run up the power rating, sure would anticipate that with our 427 gas motors or any other motor for that matter, if you ran it up to 1 horsepower per cubic inch. Some of those would never make it to the 700 hour mark, and some may only make it to the 7 hour mark depending on how they were used. Assuming the pistons and connecting rods are upgraded to take the punishment, the generation of higher power also puts a huge wear factor on bearings and I suspect also on rings and cylinder walls.

Along with the additional power comes additional heat, and this is what most likely contributed to the destruction of some of the motors we are aware of that have come apart after rebuilding (those that deviated from stock marine specs). On one example, the 427 powered 47 Commander, PARAMOUNT, had engines rebuilt and they came apart not once but twice. Although I never really heard the specific outcome of the malady, it was apparant that the intakes, carbs, and pistons were not stock, and therefore I suspect the compression ratio was not stock either. The result was more power, and the captain noted the fact that the boat seemed to move better and commented on the "more power" issue, but shortly thereafter pistons melted and connecting rods broke. It was not a pretty sight (or sound). Part of the problem was (we think) the use of
hypereutectic pistons rather than forged pistons, the hypereutectics are high in silicon and more brittle, and just will not take the punishment that forged pistons will. The engines seemed to run fine on the dyno, but when put to the task of pushing a 47 Commander, they generated so much heat and internal stress that they came apart.

http://www.youtube.com/embed/EzbW2FL9htY?rel=0
Here is the video of a 427 breaking a connecting rod and melting pistons, not a pretty sound. Marine engines used in cruisers should be rebuilt to the stock setting, becuase they get the same duty as a dump truck running uphill fully loaded.

best,

Paul


 
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