|06-25-2008 08:49 PM|
idles perfect but cruise is lean..enlarging transfer slot restrictors?
i've been working my carbs on my 671 blown 350 the past week and i have a few q's regarding cruise a/f ratios. The carbs are holley 600cfm double pumper 80575s supercharger carbs.
when i first started it up I had I was pig rich at idle and no adjusting of the mixture screws would help, so i tapped the metering block for set screws and reduced the diameter of the IFR's from .036 to .033(along with relocating the IFR's from the upper to the lower position in the HP metering block) and now I have a perfect idle. a/f is around 13.5:1(on the wideband) and the mixture screws are about 1.5 turns out.
I took it out for another ride and cruising with just the throttle cracked gives me a ~16-17:1 a/f ratio and while watching my vacuum gauge as soon as my power valve opens up the a/f drops down to about 12:1(with .055 PVCR's 69/78 jets). I havent tapped the main body for replacable CCR jets yet but they are around .065 on the primary side. I was thinking about upping them up to around .07 to see what happends...but if the problem is elsewhere i'd like to hear what people think because i'd prefer to not drill and tap the main body just yet.