View single post by Esprit2
 Posted: 05-26-2009 09:32 pm
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Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 341

If you have the option,  order the E version of the Dellortos... 40E or 45E.   The differences are in small details like fine pitch threads on the idle mixture screws.   The overall performance is unchanged,  but it's easier to fine tune the carbs.

Also, look for Lotus spec carbs.   Lotus worked very closely with Dellorto and many details in the carbs used on their engines were specifically tweaked for them.   The idle progression 6-hole pattern was specifically developed for the 9XX and makes a worthwhile difference.   Many of the details Lotus developed later became standard features across the Dellorto line,  but the Lotus progression holes remain Lotus-specific and never became Dellorto-generic.

The higher compression, all by itself, is good;  however, hi-compression also forces the need to burn more expensive hi-octane fuel.   So, from a cost efficiency basis,  is it still better?   If the goal is economy,  then HC may not be worth it.   If the goal is performance,  then yes, by all means go with hi-compression.   11:1 is a good street ratio.

JE Pistons offers high quality forged aluminum pistons for the 907 in just about any CR you could want.   I've not done a survey and don't know what other brands are readily available.   There isn't a structural reason why more pistons aren't available for the 907.   It's just demand.   It costs to develop any product,  and there just aren't enough 907's on the road to get every manufacturer excited about jumping into the market.

Consider installing the stroker 2.2 crank.   It's the best thing you can do for a 907.   Regardless of which crank you use,  use a cross-drilled version with the bearing shells that go with it.   If you stay with your existing 2.0 crank,  you can have it cross-drilled.   Then use the later bearing shell for the X-drilled crank configuration.

Last edited on 05-26-2009 09:36 pm by Esprit2