Does anyone have knowledge of how close to
"true balance"
the externally weighted
360 LA and Magnum 5.9 V8
typically are from the factory ?
Are they within, say 15 grams of zero?
Are the internally neutral 318/5.2 V8s
typically better balanced from the factory?
I know a guess always has to be made about the weight of "residual oil" clinging to the crankshaft of a running engine.
It has seemed to me that 318s have less vibration than 360s
http://www.ebay.com/gds/Crankshaft-Engine-Stroker-Kit-Balance-Balancing-/10000000013602009/g.htmlsample quote
So what does this actually mean in terms of the forces generated inside an engine? An imbalance of only 1/4 oz. (7 grams) located four inches out from the center of the crank on a counterweight will generate a force of about 7 lbs. at 2,000 rpm. At low rpm, you would hardly feel a thing. But at 8,000 rpm, that same force would grow to 114 lbs. with every revolution of the crank. If this same engine had one ounce (28 grams) of imbalance, the forces generated would be multiplied by a factor of four, generating 456 lbs. of unwanted gyrations at 8,000 rpm!
That’s enough vibration to rattle your teeth and pound the heck out of the main bearings. It’s also wasted motion that goes into shaking the block instead of spinning the crankshaft. Consequently, imbalance hurts horsepower as well as smoothness and engine longevity.
The factory balance of crankshafts can vary a great deal depending on the application and the OEM tolerances.
For a low rpm stock engine, plus or minus 8 to 10 grams or more may be close enough for the average Joe.
For a street performance engine, those numbers should come down to plus or minus 3 grams or less.
And for a high revving NASCAR engine that spends most of its time at 8,500 to 9,500 rpm, plus or minus 1 gram or less is the rule.
How much is 1 gram? Not very much. A dollar bill weighs one gram. A penny, by comparison, weighs about 2-1/2 grams. An ordinary sheet of office paper tips the scale at a whopping 5 grams, which is more than the amount of imbalance that’s generally desired in a street engine.
