Combustion chamber & twin plugs

[Thomas Burns]

Sounds pretty interesting, although I don't know why having one plug not
fire would ruin the engine?

Also... I guess I will bite and show my novice. What are "squish belts"?

-Tom

At 07:46 PM 10/1/96 -0700, you wrote:
>At 10:18 PM 9/30/96 -0700, you wrote:
>>Michael Fawke wrote:
>> 
>>Does anyone have any references to any work dealing with multiple
>>spark plugs per cylinder?
>
>The best data set I've seen is in a little pamphlet by Branch Heads (I think
>it was Branch, "Flowmetrics",??) on developing a street Harley Davidson 1320
>"Big Twin".
>
>The Harley is the most pathetic thing you've ever seen from a performance
>standpoint, a huge open hemispherical combustion chamber, big piston domes,
>pushrods, an intake system that robs peter to pay paul, iron and air cooled
>to boot.
>
>They spent weeks of dyno time trying every popular performance cam, pipe,
>carb, & head for the bike.  There is a pretty good narration that goes with
>it on their rational.
>
>The cliff notes version is that the dual plug mod is effective at improving
>Hp and reducing the amount of ignition advance required for peak power.  The
>caveat is that if one plug in the chamber fails, the timing will be too
>retarded and you will smoke that poor air cooled motor before you know it.
>
>The interesting thing is that when squish belts are added to either side of
>the chamber, peak power occurs with spark advances similar to the 2 plug
>head, and the dual plug mod no longer shows a performance benefit.
>
>Edelbrock markets a head for Harleys that uses this style of combustion
>chamber (and several port mods) that produce remarkable power gains.
>Although if you want large delta's its best to start with low initial values.
>
>Harleys are a long way from modern hot rods, but I think a lot of the data
>applies to open chamber V-8s.  Vizard indicates that a closed chamber 9:1
>350 chamber chevy 350 with dished pistons (to match the combustion chambers
>- Banks calls them "reverse deflector) are worth 20 hp over a flat top open
>chamber motor with the same cam.
>
>$.02 more.
>
>Shaun Brady
>
>
>