318 Running Richer w/ Carb Swap

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twood16

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Hey All,

Finally buttoned up a lean burn delete on my 318 in a Magnum ( I know it's not an A-Body but there's more small block experience here it appears) and it appears to be running pretty rich and I'm trying to decide if it's the carb or another issue.

Imgur Link to pertinent photos:

Before the swap:
Still fired using lean burn system with the small BBD 2 Barrel
Noticed soot on wall of garage usually after the startup/high idle sequence but not when revving
Stock engine w/ 64k miles
Oil leak from valve covers down the side of the block

Details of the Swap:
OEM E58 Intake Manifold off a 300
Holley 4175? Spreadbore - Main Jet 64, Primary Nozzle/Squirter 40
HEI Module and an OEM Electronic Dizzy from my 76 Doba based on this post here Lean burn to old style ign swap?
Troubleshooting So Far:
A/F screws turned 1 out as a baseline until we track down our A/F ratio gauge
Swapped the Primary Nozzle from another Holley I had down to a 31
Double checked float height and the needle seating as I had bought the carb secondhand
Where we are confused is the amount of soot being blown out the tailpipe both at idle and revving/driving. It runs good and has great throttle response but the amount of black smoke is concerning.

Potential Trouble Areas:
Jetting wise, would a 64 be too large for a stock smog era 318?
Previous owner had done a tune-up but thought about a potential hotter plug swap as another idea.
If need be I could purchase an adapter and see what the 4160 I stole the Squirter from does
As mentioned above we need to dial in A/F and Timing due to gauge misplacement and the discovery of a broken timing light
Sorry for the wall of text, just wanted to give as much info as I could think of to kick it off.
 
Has the fuel pump been replaced lately? You might want to check the pressure. 3 or 4 pounds is all you need. It sounds like it was running rich before the carb swap so it is probably something else.
 
toolmanmike said:
Has the fuel pump been replaced lately? You might want to check the pressure. 3 or 4 pounds is all you need. It sounds like it was running rich before the carb swap so it is probably something else.
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I have not replaced it myself and it looks like it's been on there long enough to say previous owner had not either. Would a stock mechanical pump really put out more pressure than needed? I have one on the shelf that I could swap if need be, but I'll fuel pressure check to the troubleshooting list.
 
The jets have absolutely ZERO to do with idle mixture. Nothing, nada, zilch. They are on the power circuit, which comes in well above idle. That list number is a 650 spread bore, vacuum secondary carburetor. They are really decent carburetors and can deliver a great mix of power and mileage. I would not suspect the carburetor RIGHT away. Where is your initial timing set? If it's not advanced enough, that will cause it to run rich at idle. That's the first thing I would look at.
 
twood16 said:
I have not replaced it myself and it looks like it's been on there long enough to say previous owner had not either. Would a stock mechanical pump really put out more pressure than needed? I have one on the shelf that I could swap if need be, but I'll fuel pressure check to the troubleshooting list.
Click to expand...
I have seen new stock replacement pumps put out north of 10#. You will never know until you test it. It's all part of the diagnosis. Make sure the
tune-up is correct. Like Rusty just mentioned. Check the timing.
 
RustyRatRod said:
The jets have absolutely ZERO to do with idle mixture. Nothing, nada, zilch. They are on the power circuit, which comes in well above idle. That list number is a 650 spread bore, vacuum secondary carburetor. They are really decent carburetors and can deliver a great mix of power and mileage. I would not suspect the carburetor RIGHT away. Where is your initial timing set? If it's not advanced enough, that will cause it to run rich at idle. That's the first thing I would look at.
Click to expand...
We set it at TDC before buttoning everything back up, but have only done timing by ear at the moment due to broken timing light. It runs and responds to throttle really well, but is just richer than Jeffrey Bezos. Tonight will be timing with a light, checking vacuum and fuel pressure along with a pulling plugs and taking photos so I can update this post with better info.

I appreciate both of your guys' help so far it's opened my eyes up to things I wasn't considering
 
You'll probably need to pull in on the order of around 16 degrees initial timing. That's about where I would "start".
 
Doing by ear warm up the car advance it until the started turns slow
back it off a ch and punch it
 
Update from a timing session last night. Just for a baseline we set it at an initial timing of 5 degrees.

What we discovered:
The timing light was cutting out on Cylinder 1 while setting base timing.
We checked 2 and it was firing consistently and evenly so we swapped plugged wires between 1 and 2 and 1 still had misses and 2 was fine.
Cylinder 7 with the timing light clamped closer to the plug was missing like crazy, but moving the clamp closer to the dizzy produces a consistent pattern on the light.
We changed the rotor because the new rotor had a tweaked top contact (bent to one side) and 1 cleared up but 3,7 and 8 were still missing closer to plug, but fine up by the dizzy.
Somewhat separate but it appears the plugs were gapped to ~.060 when the last tune-up was done.

Next Step:
Re-gap spark plugs to a more manageable .035 or so
Buy a new coil as it is is the one constant between the two ignition systems and it was running rich before.
Maybe snag another cap just in case even though this one is new that it's not at fault. See rotor being new but wrong.
Double check gap between reluctor wheel and pickup, maybe purchase another if nothing above changes.
 
Been following this thread,
And I would like to thank you for posting your fix for the problem.
Some people don't and that is frustrating.
I personally advance the timing more but there are some members here that know more than me.

Hope everything works out well for you.
 
Init timing seems to low. Only CD igns or HEI can tolerate 0.060" plug gaps, others should be 0.035".
 
In your photos, the choke looks partially closed. Hopefully when the engine is warm it is in the full open position. If not it needs to be.
 
TT5.9mag said:
He has an HEI.

@twood16 what do the plugs look like?
Click to expand...
Plugs were sooty, but the gapping was definitely generous considering it was just running on Lean Burn 2 weeks ago. But also would just the swap to the module be enough to gap that high with new plugs? I assumed I'd need an HEI distributor and coil to justify gapping that large.

Bewy said:
Init timing seems to low. Only CD igns or HEI can tolerate 0.060" plug gaps, others should be 0.035".
Click to expand...
Yeah it was a just baseline going off an aggregate of numbers we were finding at the moment. Fenderwell says 16 degrees but that was the lean burn spec so we just settled on a number that seemed reasonable.

Main Updates:
Coil did not change the misses
With the idle turned up to about 1500rpm there was no black smoke making it's way out the exhaust, but 2 revs in a row led to a black cloud on the 2nd rev
Finally popped the carb apart again to check the power valve and lo and behold it was wet with fuel on the backside
I assume someone has been in the carb before me as all Holley Spec sheets list the Primary Jets at 62 and these were 64 and it appears they swapped the power valve and ended up with a double gasket scenario.
Got the 2nd gasket off and put in a new power valve from another carb.
Started and died because the bowls were empty and while running around the car to pop the garage door back open I had the key on and it burned a fusible link wire.....

Based on my new understanding of the Power Valve function I'm assuming my rich idle will hopefully be cleared up now as vacuum won't be pulling excess fuel into the intake under the throttle blades. I still have to figure out the miss issue, so I'm gonna go with new plug wires next just to see as they are the only thing now that haven't been swapped out.

Oh, and an oil change since I may now have gas in my oil....
 
Holley? One backfire can blow out a power valve and you will experience rich/rough running.
 
RustyRatRod said:
The jets have absolutely ZERO to do with idle mixture. Nothing, nada, zilch. They are on the power circuit, which comes in well above idle. That list number is a 650 spread bore, vacuum secondary carburetor. They are really decent carburetors and can deliver a great mix of power and mileage. I would not suspect the carburetor RIGHT away. Where is your initial timing set? If it's not advanced enough, that will cause it to run rich at idle. That's the first thing I would look at.
Click to expand...
Thank you for telling me this. I was misunderstanding the function of the jets and thought they meant something as long as the car running, idle or wide open lol.
 
HEI & 060 plug gaps. This is with an E core coil designed for HEI. If using the HEI module with a canister coil &/or bal res, gap should be reduced to 035.
 
I took it for another run and gave it a good hit but went for a run around the back woods with a ,mate to show him the power of the 410 and give it a hit in second gear. Well it did its usual 6000 rev sideways action but pulled a big back fi while doing it.
I had a think about it and the only thi run. ng I had done was to open the plug gaps.I took it for another drive and gave it a hit but it back fired at the top end badly so I returned home and closed the gaps on the plugs to about 40 thou than took it for another run. The engine pulled to 6500 with no complaints.
So maybe as low compressuon engines like the old side valve six that my brother said ran the best it ever had with really big plug gaps, but a 11.5 comp 410 small block did not like it even with an 8 amp ignition system.
 
Bewy said:
HEI & 060 plug gaps. This is with an E core coil designed for HEI. If using the HEI module with a canister coil &/or bal res, gap should be reduced to 035.
Click to expand...
Any particular reason I'd be blowing the ignition fusible link left and right now? Negative side of coil and corresponding pin on hei module is reading almost 17+ volts and that doesn't seem right. Everything is wired based on the linked diagram
 
Also, the power valve, while it can affect operation if it gets blown, is once again not on the idle circuit, so it has no effect on idle mixture at all. You're kind "stuck" with the idle mixture you have with that old of a Holley. You CAN upgrade the primary metering block with one that has adjustable idle fuel bleeds.....but that ain't cheap. For about twice that cost you could have one of the nice little Quick Fuel carburetors that's fully adjustable on the idle circuit and the high speed circuit. You "should" be able to get that carburetor closer to right than it sounds, as it's pretty lean on the primaries, so try to get the timing sorted out first.
 
twood16 said:
Any particular reason I'd be blowing the ignition fusible link left and right now? Negative side of coil and corresponding pin on hei module is reading almost 17+ volts and that doesn't seem right. Everything is wired based on the linked diagram
Click to expand...

What's your voltage at the battery at idle?
A bad alternator, charge wiring, or voltage regulator can cause excessive voltage which can then smoke certain circuits.

If you get 15+ volts at the battery, then I'd be checking the charge circuit first, then the voltage to the alternator field to rule out the alternator or regulator.

It's uncommon to have coincidental failure but it does happy. But usually it's something related to recent changes and depending on where you tapped into certain wires, it's possible the regulator isn't functioning right.
 
Phreakish said:
What's your voltage at the battery at idle?
A bad alternator, charge wiring, or voltage regulator can cause excessive voltage which can then smoke certain circuits.

If you get 15+ volts at the battery, then I'd be checking the charge circuit first, then the voltage to the alternator field to rule out the alternator or regulator.

It's uncommon to have coincidental failure but it does happy. But usually it's something related to recent changes and depending on where you tapped into certain wires, it's possible the regulator isn't functioning right.
Click to expand...
While idling I had 14.29 reading at the battery, hot side of coil and correspondingly at the hei module. But yeah 16.5+ depending on revs on the negative side is odd. Pulled my feed to the positive side of the coil right from dark blue wire that fed to the left side of the ballast resistor that is now eliminated. I feel like I'm in another issue that probably needs its own thread now lol
 
twood16 said:
While idling I had 14.29 reading at the battery, hot side of coil and correspondingly at the hei module. But yeah 16.5+ depending on revs on the negative side is odd. Pulled my feed to the positive side of the coil right from dark blue wire that fed to the left side of the ballast resistor that is now eliminated. I feel like I'm in another issue that probably needs its own thread now lol
Click to expand...

Possibly! Bummer..
I had a similar experience though. Was working on an efi install, and then smoked the fusible link. Figured it had to be related, but in the end it was just a bad regulator which also took out the alt (overcharge due to shorted field, then the field smoked).
Checking the voltage at the field wiring will tell you if the regulator is working OK. Checking field resistance can tell you if the alt is mostly OK.
Long before the efi, and in a different car, I once had an alt with a flying short. The voltage would only spike over 3k rpm, consistently. Had to replace the alt. It was like a switch got flipped when it happened.
Probably not your problem if your voltage rises steady with rpm, which would be caused by excess field current - either a short in the field wiring, or the regulator.
 
That's a good idea. Make another thread about the charging issue and we'll have a better chance of helping you and stay unkornfrooshed. I'll be lookin for it.
 
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