Fuel Rich

[BillCT]

I rebuilt my 76 Q-Jet by Cliffs recipe #2 2 or 3 years ago, the carb seems top work fine and cruises nice, secondaries work perfectly etc. but it just runs very rich all the time.  Especially noticible at idle; it'll stink up the garage and clothes.  In order to get it to idle smooth I have to back out the air mixture screws and when I do the I run out of Idle adjustment and can't get the idle below about 900 rpm.
Motor is a 350 with  hydraulic roller 222/230 duration 509.528 lift 112 deg L/C

From my notebook when I modified the carb here are the modifications:
Cliff installed new bushings and main throttle shaft
Installed Air Bleed screws in Air Horn and Main Body, drilled to .070
New Idle Tubes drilled to .038
Acc pump discharge holes .040
Idle ByPass Air .095
Mixture Screw holes .097
Idle down channel .058
Main Jets 72
I had 40K rods in it but after talking to Cliff once he recommented we change them but I can't remember what we ended up with.  The motor had the same condition with either set.

I'll pull the top off and look at the rods but just trying to get some idea on where the best place to look. 

Thanks

[Cliff Ruggles]

How big are the idle tubes?  Do you have full control of the idle fuel with the mixture screws?  Might be getting too much fuel from the idle system, which effects part throttle A/F as well, especially right off idle when a lot of fuel is being supplied to the transfer slots.....Cliff

[BillCT]

Cliff,

Idle tubes are .038.  Yes I have full control of the mixture screws, I can stall the engine screwing them all the way in.

Bill

[Cliff Ruggles]

What compression ratio is the 350 and what heads are being used?

The cam is pretty "hefty" for a 350 engine right to start with.  Not really a problem, but it will be more efficient at idle in a higher compression engine.

In most cases, really "stinky" idle is lean, not rich.  You should fine control with the mixtures screws 3-4 turns from seated, going rich beyond that, and lean turning them all the way in.

Timing at idle is another big player in "stinky" exhaust.  What is the timing at idle, and how much if any timing is added by the vacuum unit (MVA)?.....Cliff

[BillCT]

Sorry for the late reply Cliff.

Compression is 10:1, heads are Brodix IK-180's w/64cc chambers.
I don't bother much with initial timing because I don't drive around with the vacuum line off.  Timing is 36deg at idle vacuum connected with vac advance and I run with the vacuum  off the intake manifold.  I believe this vac can gives me about 22 deg advance.

I did buy a new set of idle tubes from you and installed them, they plugged about .033.  It seems to have cleaned up the stink quite allot but now is a bit sluggish from off idle acceleration. 

When you say below stinky exhaust is "lean not rich"  are you referring to lean air mixture or lean fuel?

Bill

[Cliff Ruggles]

Running a lot of timing can result in pretty "stinky" exhaust.  With that much compression I doubt if you'd need anywhere near 30 degrees timing at idle for a good stable idle at a relatively low throttle opening.....Cliff