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GB1
08-06-2006, 10:54 AM
I was wondering if anyone knew why gear drive cars produce more hp, then chain drive. I know that it has something to do with efficiency, but I am confused.

If one looks at the MMM (pre war) MG's they produce fairly good hp, despite there small displacement and low compression.

I have read of cars being converted from chain drive to gear to increase hp, but just don't get why or how this would increase hp.

Please enlighten me.

Thanks,
Patrick

kennypinkerton
08-06-2006, 12:08 PM
Are you speaking of final drive? or Valve train?

If final drive, then chains can only handle so much torque and hp before they break. Granted you can get a modern motorcycle with close to 200hp, but it's only pushing 600-800 pounds or so.

GB1
08-06-2006, 12:22 PM
Kenny,

Crank to Cam

Patrick

kennypinkerton
08-06-2006, 12:49 PM
I would think there would be more noise, and potentially more slop in a gear driven timing system. That said... chain driven systems are almost entirely bulletproof, and I much prefer chain over belt drivin cams. Of the 5 cars in my driveway, only one is belt driven. The other 4 are chain driven... but most modern cars are belt driven. The only place I've ever seen gear drives are aftermarket (like Jegs) and only for common v-8 chevys fords and mopars.

coldplugs
08-06-2006, 01:05 PM
I don't think the method used to drive a camshaft affects the horsepower an engine can develop at all. There might be insignificant differences in the amount of power lost in the transmission of motion from the crank to the cam.

In general, it's easier to compensate for wear using a belt or a chain, and they're easier to make quiet. Cars with elaborate gear trains up to overhead camshafts produce lots of gear noise.

High performance engines have used gears, chains, bevel gears with shafts, and belts. Each has its good & bad points, but power output isn't one.

GB1
08-06-2006, 01:53 PM
Thanks, guys, I have heard about the noise.

I was just curious having bought an MMM that puts out decent power and reading that Pegaso Z102 was switched from chain to gear to increase hp.

Thanks again.
Patrick

Roger
08-07-2006, 11:48 AM
Gear drive has often been used for racing and really high-performance engines because of the reduced variations in valve timing with chains especially, and belts. This is mostly due to whip, or lash if you prefer, that can only be overcome by power-sapping tensioners.
So yes, at the extreme there is more power to be gained with gear-driven camshafts, but at considerable expense, noise etc.
It's interesting to note that many manufacturers are nowadays reverting to chain drive for camshafts rather than belts.