Any experience with HIF6's on a 3.9L?

[gbvona]

I have kept the original manifold and HIF6's on the transplanted 3.9L mill in my 1970 3500S, which I have just now started running. The engine seems to run rather lean at idle even with the jet adjustment screws all the way clockwise. The carbs have the original metering needles--me being old I have forgotten the designation, but remember checking them against the manual. Should I seek alternative needles? (Or maybe this is symptomatic of a manifold vacuum leak?)

I would also note that I have left the two vent pipes on each carb (for engine gas recirc and bowl venting) open. Anything wrong with that?

gbvona

 

[Demetris]

I would also note that I have left the two vent pipes on each carb (for engine gas recirc and bowl venting) open. Anything wrong with that?

I can think of a couple at the moment.
These ports are designed to create some vaccuum into the crankcase. If you just leave them open as you did:
A) The engine will indeed tend to run lean
B) The engine will tend to leak oil because you will have positive instead of negative pressure within the crankcase. (A problem that you mention in another post).

 

[rockdemon]

You definitely need different needles. You need a rolling road to find out which though (one familiar with carburettors)