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Carburetor running rich after rebuild

gthumb

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Looking for some help to diagnose a carburetor running rich after a rebuild. I am experiencing considerable blue exhaust, and new spark plugs are getting fouled after a short period of time (black with carbon buildup).
For a little background, the carb is a Holley 750 cfm with mechanical secondary on a 1970 Charger 440. Rebuild was necessary due to leaking fuel from deteriorating gaskets on the fuel bowls. Carb is over 20 years old, and vehicle is driven occasionally from May to October up here in Canada. Car was running fine on old (15-20 years) plugs, and the timing has not been changed.
Assuming all things being the same, except for new plugs (NGK's) gapped at .035", I would expect the car to run the way it did before the carb rebuild. Initial settings on the carb are as per most of the recommendations I've been able to read and see on the forums and videos regarding this issue.
1) The idle screw has been adjusted so that the transfer slot in the primaries is "square" in size (the car has a difficult time idling at this setting though).
2) The idle mixture screws have been turned out 1 1/2 turns out from bottoming out (tried closing them to where they were only 1 full turn out, and there was no difference in the exhaust)
3) Fuel bowl levels have been adjusted so that the fuel level is just below the opening of the sight screw on the side of the bowl.

What could be causing the car to be running rich (blue smelly exhaust, which I am assuming to be a carb issue), and what should I try to correct the situation?
Also, how can the carburetor be tested to confirm it is functioning properly? (I am assuming the rebuild was done properly).

Any suggestions will be greatly appreciated.
 
Recheck the float level. Make sure the power valve is okand the needle and seat aren't hung with dirt or anything else.
 
If you're getting blueish smoke I would think that's indicative of burning excess oil, not gas.
 
If you're getting blueish smoke I would think that's indicative of burning excess oil, not gas.
Thanks for your reply. I'm thinking it's fuel because my car was not burning oil, nor did it have blue smoke from the exhaust before. Would burning oil cause the fouled plugs? If so, how do I check for burning oil other than a decreasing oil level on the dipstick? (which does not appear to be happening)
 
Make sure your pcv valve is clean/operating properly. When were the valve seals replaced last? How many miles are on the engine?
 
Make sure your pcv valve is clean/operating properly. When were the valve seals replaced last? How many miles are on the engine?
I purchased the car in 1983 with 38,000 miles on it. It currently has 64,000 miles, and the valve seals have never been replaced, atleast while I've owned it.
I believe the PCV valve to be ok, as I hear a rattle when I shake it. Should I try to blow air through it. It is also probably more than 20 years old.
 
I would think after 40 years there's a good chance the seals need replacing. Do you get any smoke/oil residue from the breather filter or is there a slight vacuum with it removed with the engine running?
 
Can you be a little more specific regarding the breather filter. Do you mean the hose that connects the air filter to the passenger side valve cover? Which end should I disconnect to check for vacuum? Please excuse my ignorance.
 
You probably have a breather filter that pushes into a rubber grommet on the valve cover, correct? With that removed it should pull a small amount of vacuum to hold something like a small envelope over the grommet while running.
 
You probably have a breather filter that pushes into a rubber grommet on the valve cover, correct? With that removed it should pull a small amount of vacuum to hold something like a small envelope over the grommet while running.
Yes, that is correct. So I check whether vacuum is being produced from the block by putting something like an envelope or a sheet of paper over the rubber grommet in the valve cover?
 
Dumb question, but you did remember to put the power valve back in?
 
Dumb question, but you did remember to put the power valve back in?
Anything is possible, but yes, a new one that came with the rebuild kit was put in. I actually took off the primary fuel bowl today and saw the power valve in the metering block(not that I didn't think it was there). I was thinking about removing it to test it, in case it got damaged from a couple of backfires, but I read that it can be tested by seeing how the engine reacts to the idle mixture screws being bottomed out while the engine is running. I understood that the engine would keep running when the idle mixture screws were turned all the way in if the power valve was damaged. I performed this test, and the engine stalled when the idle mixture screws were turned in. For that matter, I have to believe the power valve is good.
As an aside, is there any other mistake in the rebuild process that could cause a rich mixture?
 
Idle feed restrictors are installed as well?
 
I assume it has a smelly exhaust [ petrol smell ]?
Adjust both n/seats with sight plugs out so that fuel level is slightly below the threads.

If it is still rich, then I would suspect wrong/defective carb gaskets.
 
Idle feed restrictors are installed as well?
Can you please expand/explain what idle feed restrictors are? Are you describing what I understand to be idle mixture screws (the two screws on the side of the metering block, one on each side)?
 
I assume it has a smelly exhaust [ petrol smell ]?
Adjust both n/seats with sight plugs out so that fuel level is slightly below the threads.

If it is still rich, then I would suspect wrong/defective carb gaskets.
Yes, that is the exhaust I am getting. I have adjusted the needle seats to the point where the fuel level is just below the opening in the fuel bowl when I remove the sight plugs. I check this after shutting the vehicle off. Should I do it while it is running?
As for the gaskets, they came from a kit provided by Holley, not an aftermarket no-name set of gaskets. However, how would incorrect gaskets create this situation? I'm thinking it has to do with the rebuild, because I did not have this problem with this carburetor before.
Is it possible that something internally within the carburetor was damaged during cleaning of the metal parts? After disassembly, I left the fuel bowls and the body of the carb to soak overnight in a cleaning solution. I figured if all that remained were all metal parts, no damage would be incurred.
 
I recently managed to screw up changing the power valves on a Holley using AED PVs. They come with soft rubber gaskets instead of the firm, composite gaskets Holley provides. I wasn’t cautious enough about ensuring the gasket stayed in the machined recess of the PV and it seemed to tighten up OK. But it got trapped/pinched on the shoulder of the PV gasket recess causing a fuel leak. Actually it was a major fuel leak - the engine wouldn’t even fire So probably not your problem but I’ll throw it out as one remote possibility. I learned to hold the metering block horizontal and screw the PV into it from the underside so that gravity helps keep the gasket in place.
 
Can you please expand/explain what idle feed restrictors are? Are you describing what I understand to be idle mixture screws (the two screws on the side of the metering block, one on each side)?
Idle feed restrictors are small jets in your metering blocks. There will be 2 in each block.
 
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