Your best to do a vacumm check on you manifold, then knowing that reading, use Holleys recommended chart for size,....I generally choose a size rating 2 below the recommended size, ex, if a 8.5 PV is recommended, I'll chose a 6.5 PV,....so that I can enrichen the system sooner,.....your sixpack generally runs lean, esp 340's
depending on your carb years of production, there's 2 PV styles,.....so pull it apart anyway, or buy both styles, and return the one you can't use?
Last edited by DAYCLONA; 06/24/09 07:12 PM.
.....forgive me, I'm getting old! 
