View single post by Judson Manning
 Posted: 06-20-2007 01:35 pm
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Judson Manning

Joined: 03-14-2005
Location: Atlanta, Georgia USA
Posts: 406
Pardon my dyslexia!

Spec 5 thru 9 has the 160 main jet.  On a 2.0 engine I found this jetting way too rich with EGT readings barely above 1,200^F at WOT.  I dropped down to 130-140mains to get a more preferred 1,500^F. 

Even with 135 mains I have O2 readings 12.5:1 at WOT (preferred) and 13:1 (too rich) at cruise.  The challenge with going lean on the mains is drivability.  As you drop the main size for an efficient cruise, you have to compensate with fatter A/C jets or the engine flat-spots on acceleration.  I never had the chance to experiment with a set of -5 emulsion tubes.

That's not to say I like the 'drivability' of the Spec 9.  I found my car to be unresponsive and sluggish below 4,000rpm with the 160 mains.  Plugs were always fouled, oil was always too black, tailpipe and head had too much soot, plus the previously mentioned cloud of black smoke following me.

Bottom line, I wouldn't start with 160 or 130 mains.  Our buddy Dave Andrews at the Pinto DHLA site shows a 'real world example' of a race modified 2000/2100 at:  38 chokes, 150 mains, 190 a/c, and 45 pump. 

My suggestion is to start with the 150s, but be take along several sets of mains ranging from 145-160 and a/c jets in the 160-180 range.