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Old 04-11-2010, 12:05 PM
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Bbc Gear Drive

I've been thinking about installing a gear drive on my 454? They sound sweet is there any performance benefits ?

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Old 04-11-2010, 12:42 PM
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Quote:
Originally Posted by truckboy61
I've been thinking about installing a gear drive on my 454? They sound sweet is there any performance benefits ?
The best system to absorb crankshaft harmonics and guard against valve train instability is a belt drive. Next up is a chain drive. The worst offender is a gear drive.

Crankshaft harmonics are tiny little vibrations that are set up in the crank every time a cylinder fires. The force of the piston to the rod to the crankpin twists or bends the rod journal a little in relation to the centerline of the crank. After it bends just so far, it meets resistance and springs back the other way. There it meets resistance again and springs back the other way, then the other way, then the other way, etc., etc. These little bendings happen so fast that they are like plucking a guitar string, but if left unchecked, they will fracture the crank and cause its failure. That's what the harmonic damper does. It dampens these tiny little vibrations. These little vibrations can be transmitted to the camshaft and all through the valvetrain as well. Like I said, a belt is best, chain is next best and a gear is worst at reducing these oscillations to the valvetrain.

You want the noise, install a gear. At least, now, you know what's going on in the motor and what to blame it on if you have instability or failure in the valvetrain.
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Old 04-11-2010, 03:39 PM
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Amen, Amen!!
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Old 04-11-2010, 06:47 PM
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Don't waste your time, the noise will annoy you after awhile for zero performance benefit.
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Old 04-11-2010, 07:22 PM
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I love the sound but with no benefit I can spend my money on better to improve my motor !
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Old 04-12-2010, 09:15 AM
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I've got several 1000 miles on a gear drive in my ride now. It looks like brand new inside. I can't say there has been any problems or damage it has caused. If anything it makes a lot of noise and it doesn't sound at all like a blower...if that is what it is supposed to sound like. matter of fact it sounds like a thrashing machine. I have to agree it gets annoying sometimes.

Now that I have the blower on I would much prefer to hear it rather than the constant rattling and mashing sounds. I will say that the timing is rock solid and stays put every time. I did check the cam timing over the winter and it was right on so there has been no wear what so ever.

Since this car is a rolling test bed I'm going to leave it there for a while. I am testing and proving or disproving many things which I will comment on as they develop.

If there are disturbing harmonics I can't prove or disprove that as there is no easy way to check them. If I don't have a failure directly related to the gear drive then I'd have to say they are no better and no worse than a chain. Otherwise some very convincing proof and hard evidence other than hear say will be necessary. My only comment is that they do make a racket. If you like this go ahead an use them. I'm not taking this one out until it fails or causes something else to fail purely because I want proof in hand.

As far a harmonics go I don't run a harmonic balancer either with the blower. The belt provides considerable dampening and I feel the blower inertia is considerably higher than any balancer can be so I'll leave it as is. I run this way a number of times before and never had problems. Plus I don't need an expensive SFI damper.
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Old 04-12-2010, 04:30 PM
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If you want to run a gear drive do it. I've always heard a lot of opinions from many different rodders who all have their own spin on what happened to a guy they knew who ran a gear drive. I could make an argument that the chain slack and stretch that happens to a chain is actually more damaging than any harmonics that could be vibrating through the gears on a gear drive.
Its all hear-say/personal opinions. I've never met one person who's had a failure on their motor due to a gear drive. I have heard of someone who installed a cheap timing cover and the button on the gear drive ate up the cover. *shrug* Never heard of these 'vibrations' tearing up your lifters, eating up a cam, or destroying your rockers/valves/springs. The entire motor is rattling it cant be any worse than whats already happening from all the parts making the block rattle in its mounts.

I run a gear drive and enjoy the added mechanical noise it creates making my car sound even more If i ever have an issue with it ill be sure to take proper documentation/pictures and try to keep anyone away from having a similar problem. Even still, like i said, if you dig it - use it. Dare to be different! Main reason i run one.
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Old 04-12-2010, 05:02 PM
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One of the major cam companies used to show a film about internal harmonics. At engine builders seminars.

When you see pushrods vibrating like tuning forks and the gear drive slamming away at the front of the engine. You would never use one again.

A belt drive is the first choice to use for high horse , high rpm engines.
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