Holly 6211 running rich at idle

[daveL82]

I've been working on an old 6211 Holley spreadbore double pumper and through swapping parts from other 6210's I been able to get the old 800cfm working reasonably well. Previous attempts with the carb had it running so rich it would hardly run.

As of last night the timing is set and the secondary idle was set with 10th of the slot exposed. The carb ran a bit fast at 1200rpm so I lowered the rpm with changing both primary and secondary idles together trying to keep the butterflies at nearly the same angle.

I know have a slight rich condition at idle which causes the primary mixture screws to have no effect. If I pull a plug off the manifold the rpm rises and it smooths out a bit more so this tells me I have a rich condition.

Any suggestions on where to look to resolve rich idle condition? FYI- floats are adjusted, all new needle and seats, 64 jets on primary which should have no effect at idle, new 4.5 power valves installed.

 

[pcf_mark]

If you can screw the idle mix screws in all the way you have a fuel "leak" somewhere internally or someone has hot rodded your carb. If the power valve was bad you would have black smoke puffing out and I have never personally seen one blown. Dry rotted yes, blown no.


The idle mix screws circuit is fuel from the metering block mixed with air from the air bleeds on top (outer, larger set) If you inspect the metering blocks check to see if someone has drilled out the idle jet bushing in the block. I do not know the approx size for the spread bore but on a 4150 it is around .030 to .035. I recently had a block crack because I was drilling it and it was getting fuel into the idle circuit and running rich. Then check the out air bleed on top. This is the air part of the equation and if this is blocked or dirty the carb will run rich. See if someone has been in that area too. Usually people drill these and it makes the idle lean not rich. If yours have any plugs that have been re-drilled check them. On a 4150 they are around .073 but again I do not know the spread bore.

Check your metering blocks and main body for flatness too.

With the car running and some safetly glasses look down the carb and see if fuel is dripping from the boosters. If so your main circuit is pushing fuel into the boosters. Could be a high float level or leaky passages. The idle fuel is below this point and you should not see it.

Hope this helps some.

 

[daveL82]

These 4165 style carbs really have me stumped. I pulled the metering plate that was running rich and put one off another spare carb and that plate wouldn't idle at all like there was no emulsion from the idle circuit.

I was so fed up I was ready to throw the carb parts in the trash. However today I got home from work, opened a beer, and decided to put yet another metering plate from yet another spare carb. When I swap them over I reused the same jets and same brand new 4.5 power valve. The carb now idles and the idle mixture screws actually work. At a loss but making progress I guess.

Now to hook up the choke and throttle cable.

 

[pcf_mark]

Nothing for nothing but that power valve is wacky! Do you have some beast of a cam? The PV is usually the idle vacuum divided by two plus .5. It is going to wait a looong time to open when you stomp on it. Just a thought.

Something is not flat is my guess.