Re: Crank types (was "engine weight")

[bearbvd@domain.elided (Greg Hermann)]

At 1:55 PM 7/31/02, Leslie J. Singh wrote:
>At 01:23 AM 7/31/02 +0000, you wrote:
>>**weight between 1300, 1600, 1750, and 2000
>>engines?  **
>>
>>The 1300 and 1600 will certainly be lighter with their
>>single counterbalance crankshafts.  Those cranks weigh
>>nearly 1/2 the weight of their fully counterweighted
>>brethren.
>>I suspect the fully counterweighted crank allows for
>>smoother spinning at higher revs.  Adriansen's
>>book  'Alleggerita' shows an Autodelta 1600 crank that
>>was fully counterweighted.  I've always wonderered if
>>the 1600's found in later european '70's-and-on Alfas
>>ever utilized a fully counterweighted crank, could be
>>the hot setup!
>>
>>Steve Schaeffer
>>Seattle, WA
>>'65 GTA 1600 w/single counterweighted crank

Les--

Per my earlier comments, I think you will find that there is _NO_ weight
penalty associated with using an eight weight crank. Only the benefits
described.

There are certainly weight--and polar moment--benefits to be realized from
a combination of core drilling the crankpins and undercutting and
knife-edging the counterweights, if one wishes to spend the time. Take a
peek at the cranks which outfits like Scat and Crower offer for small block
Chevy "sprint car" engines to get an idea of what kind of detail machine
work I am talking about here.

Greg
>
>This topic is of great interest to me right now because I have located a
>GTAm crank which has been lurking in the back of a garage since the 70's.
>It is rusty and #2 journal is badly corroded but because of the rarity
>value I am considering a swap with a nitrided 1600 crank that I've got,
>suitable for a GTA  The crank is the genuine Autodelta one with the 8
>counterweights but I have been debating whether it offers significant
>advantages to a standard crank when used in an engine that will be revved
>to only around 7000 maybe 7500 during adrenalin rush. The weight penalty
>seems huge although it should be possible to lighten it somewhat by
>machining. Some machining will be required because #2 journal has to be
>undercut then built up and machined to size. (Steve - am sending you a
>picture of the crank.)
>
>Les in Wellington, New Zealand
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