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Author Topic: 69Z rear ratios  (Read 2474 times)
MyRed67
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« Reply #15 on: November 19, 2013, 11:48:24 PM »

They have even gone to using Aluminum Driveshafts in some cars.  I know in the midd-90's Chevy even offered it as an option on Z28's.
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1967 Camaro  LOS  11A
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Mike C.    NW - Illinois
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« Reply #16 on: November 20, 2013, 11:09:48 AM »

They actually offered it in 1988 on the 1LE.
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James
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Check out the Black 69 RS/Z28 45k mile Survivor and the Lemans Blue 69 Z 10D frame off...
https://picasaweb.google.com/112392262205377424364/1969_Z28_Restoration
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« Reply #17 on: November 20, 2013, 11:22:13 AM »

They have even gone to using Aluminum Driveshafts in some cars.  I know in the midd-90's Chevy even offered it as an option on Z28's.

The Viper has had an aluminum driveshaft since day 1 (1992).
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« Reply #18 on: November 20, 2013, 03:30:34 PM »

reciprocating assemblies in engines are one of the best ways to gain power... you are accelerating each piston from a dead stop 2 times per revolution... think about that.
Good point, and often overlooked. When I rebuild my 302 (well, 306 now), I'm planning to use 6.0" rods to reduce the piston pin height, and therefore reduce piston mass.....
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Tim - New South Wales, Australia
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« Reply #19 on: November 20, 2013, 05:29:57 PM »

This has gotten off topic,
However often overlooked advantages of the longer rod are less side force because of the decreased angular loading,  the piston has more dwell time closer to TDC which allows more pressure to build before decent, plus the longer rod is a longer lever which allows it to do more work with the same input.

I've considered a 6.125 or 6.25" rod 302 with a full roller and see what I can get out of it, run a single gapless ring so as not to worry about the short compression height and getting into the ring lands...
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James
Collectin' Camaro's since "Only Rednecks drove them"
 
Check out the Black 69 RS/Z28 45k mile Survivor and the Lemans Blue 69 Z 10D frame off...
https://picasaweb.google.com/112392262205377424364/1969_Z28_Restoration
JohnZ
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« Reply #20 on: November 21, 2013, 10:25:51 AM »

the longer rod is a longer lever which allows it to do more work with the same input.


Actually, the longer rod doesn't contribute to doing more work with the same input - the component that influences that is the stroke length - the stroke length is the lever in that system.

Imagine a front view of the engine with a crank throw at the 90* (3 o'clock) position; it doesn't matter whether the rod is 6 inches long or six feet long - the force imparted to the crank by the rod is the same. What matters in terms of a lever is the distance from the crank centerline to the big end of the rod, which is the stroke length.
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« Reply #21 on: November 21, 2013, 01:43:02 PM »

John,

What FirstGen was saying is that due to the rod 'angle' relative to the crankshaft throw during combustion (and the power stroke) that some of the energy available from that combustion is actually applied to the cylinder walls - thru the piston sidewalls/skirt, and not 100% to turning the crankshaft.  That results in 'lost energy', increased wear to the skirt and cylinder walls, etc.   That said, *nothing* is perfect, and everything we do is a compromise of one form or another..  and IF you can have a longer rod (for a given stroke), then that loss and increased wear is reduced.  If you took all those things to an extreme though, made the rods very long, the engine would have to get larger/heavier to accommodate it, or the piston pin heights shorter, which involve a lot more problems (ie.. every design is a compromise).

Smiley
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Gary W.  /  69Z28-RS, 72 B 720 cowl console rosewood all tint
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« Reply #22 on: November 21, 2013, 05:43:24 PM »

John is right in his correction of my statement, the stroke is the lever.  I knew something was wrong, got ahead of my self, and didn't proof my statement.  
That being said yes there would be more energy available to move the vehicle instead of increased friction/heat output due to reduced side loading.
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James
Collectin' Camaro's since "Only Rednecks drove them"
 
Check out the Black 69 RS/Z28 45k mile Survivor and the Lemans Blue 69 Z 10D frame off...
https://picasaweb.google.com/112392262205377424364/1969_Z28_Restoration
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