Pig rich mixture at idle 2 x 4 Gen 2 hemi

[Dragon Slayer]

Wouldn't you be starving four cylinders and creating a super lean condition in those cylinders by closing off one carb?

I first tried a progressive linkage on my 2x4 and had a lean condition on the front four cylinders that was way too hot. That was with a working carb.

Not starving, but there could be distribution issues. The street hemi worked that way. Marginal contribution from the front carb for idle. The car ran on one carb through cruise. The primary did not open until the progressive linkage opened them. Using modern carb doesn't address the way original hemi carbs were set up with jetting and distribution tabs to ensure better mixing and distribution.

 

[Dragon Slayer]

That is correct. the idle jet is in the .031" range can be more depending on carb. The idle restriction is much more than the main jet with a rod inserted. The well has the fuel. You running a street hemi manifold correct? That is dual plane and one side feeds 4 and the other side feeds the other 4. Both carbs communicate via each plane. Driver side carb bores feed 2, 3, 5, 8 and Passenger side feed 1, 4, 6, 7

 

[moparedtn]

That is correct. the idle jet is in the .031" range can be more depending on carb. The idle restriction is much more than the main jet with a rod inserted. The well has the fuel. You running a street hemi manifold correct? That is dual plane and one side feeds 4 and the other side feeds the other 4. Both carbs communicate via each plane. Driver side carb bores feed 2, 3, 5, 8 and Passenger side feed 1, 4, 6, 7

He posted right at the beginning it's a Stage 5 (V)hemi intake.

 

[pnora]

I do have O2 sensors on both banks and they read like it’s running lean but my nose says otherwise and the fuel is getting in the oil and the plugs are black.

Well if you do have correctly working sensors they most likely are not lying. What are your readings?

 

[pnora]

Another thought is weak spark. Seems like you are not changing anything with what you have done so something is messing things up. I would try a coil.

 

[pnora]

This is a simple tool that you can adjust to see what your coil is capable of.

https://www.thexton.com/ignition-spark-tester-p-34.html

 

[Hemirunner]

5.5-6 psi

You can push fuel past the needle and seat at that pressure unless you have the off-road needle and seat set up. Ideally, if you want that to idle down, you’ll need more advance. Crank all 4 screws shut one by one and see what it takes to kill it. That’ll tell you if it’s pulling fuel out the boosters or from somewhere. If it’s putting fuel in the oil, that’s pig fat.

 

[AR67GTX]

I do have O2 sensors on both banks and they read like it’s running lean but my nose says otherwise and the fuel is getting in the oil and the plugs are black.

it took me a long time to get this through my thick skull but a stink at idle is just as much or more likely due to a too lean idle mixture. The mixture is so lean it doesn’t ignite efficiently and incompletely burned gas fumes stink up the exhaust. In extremely lean conditions it will misfire back through the carb. I believe a rich idle is less pungent smelling. Probably to a really experienced hand with a good nose he can distinguish an exhaust that is running overly rich from the exhaust running overly lean just by smell. On a Holley and variants you can reduce the size of the idle bleeds to strengthen their vacuum signal and richen the idle fuel rate. Probably can do the same thing on Carters and Edelbrocks but I never have done so.

 

[Beekeeper]

Well if you do have correctly working sensors they most likely are not lying. What are your readings?

It’s reading right around 19.5 to 1

 

[Dragon Slayer]

He posted right at the beginning it's a Stage 5 (V)hemi intake.

I must have missed it, I read at the first post Stage V heads. NO?

 

[Beekeeper]

Another thought is weak spark. Seems like you are not changing anything with what you have done so something is messing things up. I would try a coil.

I will for sure find a new coil and give it a try. Anyone have a good one in mind for the dual point distributor?

 

[pnora]

It’s reading right around 19.5 to 1

I would be curious if you slightly choke off the air with a rag at the carbs if the mixture goes richer on the A/F gauge.

 

[Beekeeper]

Dragon Slayer,
That’s correct I didn’t specify intake sorry. Yes it’s a Stage V intake

 

[Beekeeper]

I would be curious if you slightly choke off the air with a rag at the carbs if the mixture goes richer on the A/F gauge.

I could give it try also I have been thinking really hard on the plugs I have in it.
I should just get the ones hemirunner recommended and see if that might change anything NGK BP5ES I think we’re the ones.

 

[Dragon Slayer]

You are running a cold plug and they can foul easy on a hemi probably even more so with a Stage V manifold and all that idle fuel and points. Granted you have high compression, but you might want to try a hotter plug as you sort this out.

 

[AR67GTX]

You don’t need anything unusual - just a good quality coil. The coil specs are in the factory service manual for a dual point. From memory they are roughly a primary resistance of around 1.2 to 1.6 ohms and secondary of 8,000 to 12,000 for 1966.

 

[RemCharger]

I would be curious if you slightly choke off the air with a rag at the carbs if the mixture goes richer on the A/F gauge.

Is this still on a run in stand? Make sure there's no air leaks in the exhaust, and the 02 isn't close to the exit. Other possibility is misfiring, which is showing up as lean, (unburnt 02)

 

[RemCharger]

Hotter plugs, more advance.
As stated.

 

[Beekeeper]

Is this still on a run in stand? Make sure there's no air leaks in the exhaust, and the 02 isn't close to the exit. Other possibility is misfiring, which is showing up as lean, (unburnt 02)

Yes still on the run stand I have the headers on and put the O2 sensors in the header adapter and attached 24” length of straight pipe to each adapter.

 

[RemCharger]

Pic?