Quote:
Originally Posted by super9064
I knew there would be a good answer to this, I just didn't know what it was, Thanks. 
With the original 911R/ 906 spec motor they used twin plugs because the piston had a high dome and the head design not optimal. but what if you are using later heads, like from a 71T, that flow better, and compression that is 10-1 or less. Cost no object , great, but it looks like twin plugging adds at least $3,500-4,000 to the build. I'm trying to be a bit more economical these days while still being extravagant.  |
The later heads (2.2-2.4-2.7) are not as octane sensitive as the 2.0 heads so you can get away with a bit more compression before requiring twin-ignition on pump gas. Bore size & camshaft profile plays a big role here, as well.
People having access to 93 octane gas have more flexibility than ones with only 92, too.
More information on this subject can be found here
http://www.rennsportsystems.com/2a.html