Bill 3

Put O2 bungs in over the winter. Finally close to getting the carburetors dialed in. NA 515 cu.in. 850 holley's (4150), just under 600hp on the dyno. 6.5 PV front and back, Jets 88 front, 87 rear. I pull about 8" of vacuum at cruise.

In my cruise range, AFR is bouncing around 13 and my WOT is in the upper 10s.

I need to jump to probably 90 in the front (to get closer to 12) and possibly drop to 86 or 85 in the rear (to try and end up around 11.5).

Seems odd to me that according to the O2 sensors, I need this much more jetting in the primaries.

Is this something I should be concerned about? Possibly the wrong carburetors for the application?

SB

iTrader: (1)

I think you are getting confused thinking that only your primaries are open during cruise.


Edit in: remember, you are running frt and rear PV's, so your jetting will stay closer to 'square' than the more typical 1 PV and one plugged.

Bill 3

I say primaries, I am referring to the front. At cruise, I am only using the front (primary) jets of the carb and the PV is closed.

SB

iTrader: (1)

Are you 100% certain your secondaries aren't open at all ? And how did you check this ?

Bill 3

Mark on my throttles where the secondaries open. Double pumper.

SB

iTrader: (1)

Okay, good.

Anything replaceable on this carb like air bleeds, Power valve channel restrictions, or etc ? 4 corner idle or 2 ?

ezstriper

ok, what you want to do here is enlarge the power valve channels, depending on the carbs(quick fuels have removable ones some others as well) tuning here will not kill the idle,low speed AFR's. Air bleeds are another, but unless they are changeable I would not mess with those. also if you are 8" of vac at cruise, try a 10.5PV

Bill 3

Nothing replaceable. 4 corner idle.

I will say that I should double check my throttle to verify the secondary opening. If by chance it is opening, it would be just barely.

You do have a good point though, when I get up past the secondary opening, my AFR does not go up until I get close to WOT when the PVs are open, then I am a little on the rich side.

SB

iTrader: (1)

IS this an 0-80443 ? Holley lists 88p 96s jets and 1 power valve 6.5"

Bill 3

Holley 0-4781S I wanted 4 corner idle.

It doesn't appear that much time was spend on tuning these carburetors. On the Dyno it seems they only were after the upper rpm range, 4500 plus. Jets were 85 and 88. Midrange AFR was 14 even into the secondaries when I first put in the O2. Idle was near impossible. I have worked on the idle a lot and have it idling pretty well now.

You have me second guessing myself on where the secondaries open, i need to verify the exact spot where they start to open. I may need to dump more fuel back there and get the PV to open sooner.