Carbs Running Rich Cause This?

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JD Erisman

JD Erisman

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I pulled my 408 stroker’s six pack intake off to fix an oil leak, engine has about 3,000 miles. I noticed what I’m assuming is carbon fouling on every valve, see photos, please.
I have have been fighting rich idle and cruising AFR since installing the six pack. I am making headway and have made AFR improvements and will continue to do so. Is it worth trying to clean this fouling off the valves? If so, any suggestions on how other than removing then disassembling the heads?

Separate note, I have Hylift Johnson lifters made by Topline Automotive in Michigan. I’ve had a ticking noise since building the motor, all RPMs, mildly worse on start-up. No exhaust leaks, checked everywhere but changed the header flange and collector gaskets anyway. With the valve train still on the heads I cannot collapse any of the lifters when pushing on the rockers. Since the intake is off, any suggestions on checking the lifters for a bad one? Pull them all and try to collapse them another way?
Thanks for any suggestions.

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I'm going to say no, and no.
Rich is (relatively) cool. IIRC hottest is just below stoich. Then it s gets cooler again.

Carbon in the intake tract is from reversion. That's really only low rpm. That doesn't look like carbon in the photo. Bad reversion is when there's residue in the plenum or even the into the carb.

Sidetrack if you haven't seen this racingfuelsystems-Desired Carburetor AFR Characteristics At Different % Load
 
The heads are Trick Flow.
The only time I have lean conditions, according to my gauge, is when I go wide open, then it goes very lean. I’ve been working to correct that and have made some progress.
The material on the valves appears wet, which I thought would indicate a constant rich condition at idle (it’s less than 11:1) and rich at low to mid range cruise (12.5:1).
IDK what the heck I’m talking about though.
 
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Cam and ignition timing plays a big role in idle tune up quality

What's initial timing set and camshaft in the engine? Even a stock 340 6 pak liked 16-18 initial timing to start out.

Idle at 11:1 afr, it's killing the plugs if correct.
 

JD Erisman said:
The only time I have lean conditions, according to my gauge, is when I go wide open, then it goes very lean. I’ve been working to correct that and have made some progress.
Click to expand...
The gage can lie. Or more correctly described the WBO2 conversion to AFR can be thrown off by conditions in the chamber not quite as assumed.

That said. Going lean at WOT is dangerous. How lean is the gage showing? RPM? Gear?
Look at the spark plugs.

Cruise. Work on that and idle. At some speed (mph) the power to keep the car moving will require throttle opening where the main circuits are providing the fuel. Below that speed the 'idle circuit' is providing the fuel. Where that transistion completes varies but somewhere between 50 to 65 mph.

Even at 60 mph, a slight downhill or letting off of the throttle will put it back on the 'idle circuit'. Furthermore, its fairly high vacuum. I posted a table of AFR measured for rpm, vaccuum here. But read the link above first.
 
Initial timing is 16°. Cruise RPM, 3rd gear in the 727, is about 2,500/2,600, at that RPM the AFR is about 12.5:1.

At a WOT stomp in 3rd gear the AFR went all the way to 17.5:1 at 6,000 ish RPM. Same happens if I go WOT from a complete stop.
Timing is 32° at 2,500, total advance is 50°.
The plugs aren’t horrible but they are slightly carbon fouled. Depending on the cylinder some plugs are slightly, but noticeably, better than others. I have cleaned them a few times.
I tried leaning the AFR by adjusting the idle mixture screws, it leaned it but it didn’t drive as well with normal driving, accelerating from stops.
 
JD Erisman said:
I pulled my 408 stroker’s six pack intake off to fix an oil leak, engine has about 3,000 miles. I noticed what I’m assuming is carbon fouling on every valve, see photos, please.
I have have been fighting rich idle and cruising AFR since installing the six pack. I am making headway and have made AFR improvements and will continue to do so. Is it worth trying to clean this fouling off the valves? If so, any suggestions on how other than removing then disassembling the heads?

Separate note, I have Hylift Johnson lifters made by Topline Automotive in Michigan. I’ve had a ticking noise since building the motor, all RPMs, mildly worse on start-up. No exhaust leaks, checked everywhere but changed the header flange and collector gaskets anyway. With the valve train still on the heads I cannot collapse any of the lifters when pushing on the rockers. Since the intake is off, any suggestions on checking the lifters for a bad one? Pull them all and try to collapse them another way?
Thanks for any suggestions.

View attachment 1716530725

View attachment 1716530726
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Thats crappy fuel.
Those are trickflows for sure.
Everyones heads on the street probably look like that.
 
I think air fuel gauges can be a little tricky with a six pack it can get you close but there's a lot going on there during the transitions some ports want to run lean and some ports want to run rich kind of the nature of the beast. you can go crazy chasing it. Read the plugs. As far as your pictures it doesn't look rich to me I would agree that it's getting hot and maybe leaning out at some point.
 
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I have your exact same set up. My intakes look the same way. My cam is in at 106°. Initial is 20-22, total is 34. Yellow springs in the diaphragms, primary jets are 62-64 ,ends are 72-71. 8.5 power valve. My cruise AFR is upper 14's to very low 15's. WOT is mid 13's.
I too have a lifter tick, have tried different tappets and at present, treating it like a solid, lashed at .010 cold. I've gotten used to the tick!
My plugs all look a little different, this set up seems to always be hard to read.
 
Thanks for everyone’s input.
I’m going to read from the two links Mattax provided. I may try running AV gas 100 octane, otherwise the best pump gas I can buy is 90 octane. I’m just curious if I notice a difference in the plugs condition.
Dat Frog, I have noticed the disparity in the plugs condition can vary widely between cylinders. The six pack definitely requires more patience.
 
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JD Erisman said:
Initial timing is 16°. Cruise RPM, 3rd gear in the 727, is about 2,500/2,600, at that RPM the AFR is about 12.5:1.

At a WOT stomp in 3rd gear the AFR went all the way to 17.5:1 at 6,000 ish RPM. Same happens if I go WOT from a complete stop.
Timing is 32° at 2,500, total advance is 50°.
The plugs aren’t horrible but they are slightly carbon fouled. Depending on the cylinder some plugs are slightly, but noticeably, better than others. I have cleaned them a few times.
I tried leaning the AFR by adjusting the idle mixture screws, it leaned it but it didn’t drive as well with normal driving, accelerating from stops.
Click to expand...
Are you saying total "mechanical" advance is 50 degrees? You probably don't need much more than 32 with those heads.
 
JD Erisman said:
At a WOT stomp in 3rd gear the AFR went all the way to 17.5:1 at 6,000 ish RPM.
Click to expand...
Even if the plugs don't look white I wouldn't do that again.

JD Erisman said:
Timing is 32° at 2,500, total advance is 50°.
Click to expand...
Idle timing is at least ballpark. 32 at 2,500 is too quick although you can do that with no vacuum advance.
Something around 22 at 2500 and 32 at 3500 is more like it, especially with vacuum advance.
JD Erisman said:
The plugs aren’t horrible but they are slightly carbon fouled.
Click to expand...
How 'bout specks of aluminum? That's the concern when running lean and too much advance under heavy throttle.
JD Erisman said:
I tried leaning the AFR by adjusting the idle mixture screws, it leaned it but it didn’t drive as well with normal driving, accelerating from stops.
Click to expand...
I'd do this. Don't worry so much about the AFR number but do keep track of it as a reference.
It may need a little richer off idle.
But it needs to get the fuel another way, not through the idle ports bu tthrough the transfer slots.

Try this first.
Turn the mix screws in until the rpm drops or you hear it miss or slow. Turn them back 1/4 turn.
Normally that's going to be a pretty good idle when placed in gear.
So place it in gear an note the rpm drop.
Write down how many turns out from closed each of the screws is.

Is that more or less than were it drives best?

The reason for writing this down is that is the baseline where it works.
Next either experiment with the throttle opening and intial timing, or restricting the Idle Air bleeds.

For the throttle opening, increase the initial timing a degree or two. Then bring the rpm back to your baseline by slightly closing the throttles at idle. Write down the amount the screw was turned along with the timing and rpm info.
Now with the slightly more closed throttles repeat the fuel trim adjustment.
Then place in gear and note if there was less or more rpm drop. Less drop is stronger idle.

You can repeat this a few times until finding the strongest idle at X rpm.
Then take it for a drive and see if there is a flat spot coming off idle.

If there still is, get some wire and stick it in the Idle Air Bleeds. That should help or resolve the off idle lean.
The wire will need to be pretty big. If the air bleeds are .070" diameter, wire around .030 should make a noticible difference.
Run the wire over the air horn and under the gasket for the air cleaner or some other secure manner.
 
JD Erisman said:
I’m going to read from the two links Mattax provided. I may try running AV gas 100 octane, otherwise the best pump gas I can buy is 90 octane. I’m just curious if I notice a difference in the plugs condition.
Click to expand...
If they are overwhelming come back to them another time.
The main take away is that engines need to be 'rich' idle, and leaner as the throttle opens, and then rich again under heavy load near full throttle. To throw some numbers at it, warmed up idle strongest AFR could be 12 to high 13s, and WOT strongest will probably be mid 12s to mid 13s.

90 octane may be limiting. It won't effect initial but I'd definately run less advance under higher loads. Density of 100 and 90 should be similar. In other words not going to effect AFR much if at all.
 
Cruze 418, I learned the hard way about AV gas ruining my Auto Meter AFR sensor. Expensive lesson I don’t want to repeat, thanks for the reminder. I like your AFR numbers. What cam are you using? I will play with the outboard’s springs. I installed ProMax metering plates but my jet numbers are lower than yours, maybe I will move up in number.

Mattocks,
I will reset my timing at 3,500 instead of 2,500 and I’ll play with moving it up and note the changes. I don’t know where I came up with 2,500 but it appears wrong. I will try different settings beyond 32°. I will take your other steps too, including the wire in the air bleeds. Which air bleeds do I plug, inboard or outboard?

GGress, my total timing, initial plus mechanical with vacuum advance connected is 50° but I don’t remember the RPM. I think that’s the number from my old Mopar Performance engine book.

Thanks to all for your advice.

 
yes leaded gas will greatly reduce the life of your Lambda sensor

i.e days/weeks rather than years .

fine if you have a mobile unit and are just sticking it up that tailpipe to do a quick check
but one bolted into the system won't survive long .

ATF on a tooth brush will bring the black gunk off the valves brush it on leave it a day or two then run the engine

cleans em up

why?.....search me... I dunno...

dave
 
JD Erisman said:
I don’t know where I came up with 2,500 but it appears wrong.
Click to expand...
It's very common in the hot rod world to see that. It seems to come from drag racing experience in the days of points ignition.
For 1/4 mile racing, the engine is not heat soaked little bit of additional advance at the low rpms can help offset the slower burn in the colder chamber. With points there was no delay from the electronics (retard) so 32 at 3000 would be 32 at 6000 rpm. Why people are still doing this? Prob because most are just repeating what they heard but not digging into the why it worked.
JD Erisman said:
I will try different settings beyond 32°.
Click to expand...
If people are saying those heads don't need more than 32° then stick with that. The more efficient a head is the less lead time will be needed.
JD Erisman said:
GGress, my total timing, initial plus mechanical with vacuum advance connected is 50° but I don’t remember the RPM
Click to expand...
Yes. 50° is about where it should be with vac advance cruising on an interstate highway, or whatever you have up there that's 55 - 75 mph.
JD Erisman said:
I will take your other steps too, including the wire in the air bleeds. Which air bleeds do I plug, inboard or outboard?
Click to expand...

In general I'd say try to get it to work with just getting the transfer slot and initial timing adjust to strongest when placed in gear.
Idle Air Bleeds (IAB) are outboard.
Looking at my spread sheet; a single .020" dia. wire will reduce a .076 bleed to the equivalent of .073, and an .070" bleed to and .073 equivalent. That's a reasonable step/change to test.
An .030" diameter wire will reduce a .076" bleed to a .070" That's a big jump.
(see bottom of this post for more wire size vs. hole size)

I haven't worked on a 6 pack and don't know if I have any specs copied down. I know there a couple of flavors of these carbs. Since you have the intake off, at minimum it would be worth measuring how many turns of the idle stop screw of the center carb opens the transfer slot to expose .020" to .040" under the throttle blade.

With carb off the engine check the primary transfer slot exposure under the throttle plates at idle are in the range of .020 - .040"
If it gets out of range, then there will be a delay or bog while driving or accelerating as the throttle opens. explanation here
You can check with feeler gage or drill bits.
1775824047119.png

The drill bit is next to the transfer slot.
The hole is the idle port.
Write down how many 1/4 turns in of the idle speed screw from just touching gets .020, 030, and .040.
Then you'll always know how far open the throttles are without removing the carb from the intake.

Fully measuring the restrictions of center or all carbs would be a good reference for future.
 
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I assume they are hydraulic lifters, on mine (small block with trick flows and hydraulic roller) I had to play with the lash a lot to get it just right.. a bit too much preload, noise.. too little.. noise.. I lashed them like 8 times trying small changes each time.. i ended up at 1/4turn and no more noise... I didn't have johnson lifters though.

P.S. this is where having a starter trigger under the hood and doing them EOIC really helps speed things up
 
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Mattax said:
Fully measuring the restrictions of center or all carbs would be a good reference for future.
Click to expand...
Body with old gasket on it. Impressions show the Air well and Idle down well.
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This is from one the Plymouth the Service Manuals showing an emissions carb. I've crossed off the items your 2300 won't have.
1775825969583.png



Below is from Urich's Holley Carb book
The idle feed restriction (IFR) usually is at 25, sometimes now at 6, and occassionally will be in the middle of the well.
The "emulsion bleeds" are the bottom of the lower two holes marked 22. The top hole is a kill bleed, if present, and 8 is only pressent if there is a tube in the main well.

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You can make a spread sheet or a notebook list of the restrictions and measure using a the shank of small drill bits.
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Distribution on the 6 pack isn’t very good. I get about 3 years on an o2 sensor making 150 passes a year running c12. Fix the WOT lean, you WILL hurt stuff. The stuff on the valve, do you have the plugs from the lean run? Look at those with magnification. Looking for small silver balls or deposits of aluminum. I would not pull the head just to clean it off. If it comes apart, I would clean them. I wrap tape around the valve stem and lightly put them in my drill press. A brass brush and carb cleaner does the trick. Just went through this and had a maroon deposit on the exhaust valves that was STUBBORN, used a razor to scrape it off. Pretty sure it was lead. Red scotchbrite does well.

IMG_3179.png
 
I have a Howard's hydraulic roller with 1.6 rockers. The transfer slot on my center carb is very close to square, it will idle at 600 rpm if I want. Rember that all 3 carbs contribute. I adj the ends by putting a finger or thumb over the outside air bleed, if the rpms go up, it's lean, if it goes down it's rich. I have about 15-16 in of manifold pressure. If your hearing isn't great, you can use a vacuum gauge for adj to the highest reading. Be careful when tightening the carb bases down, they don't need alot. Sometimes you have to move the outboards around, usually forward or back, so that the throttle blades do not hang up on the gasket. I like thick gaskets vs thin, if you are taking them off and on alot, they don't last forever.
I have the tall yellow springs in the diaphragms, purple would work too.
Do you have a bog when you go to wot at say 2,500? It's not always the springs, it can be fuel, wants more.

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Can you post some pictures of the intake flange to head flange gaskets/surface. Often times if the surfaces are not exactly parallel, oil can get sucked in from the valley on the bottom side of the intake flange. The valve seals have left the stems looking great.

Also, If you add an additive that cleans deposits such as Techron or similar additives, it will melt that off the valve and reduce deposits.
 
My intake doesn't leak, I checked that. I did put an oil mist separator between the pcv valve and the carb. I haven't had the intake off for a year or so, do not know if that stopped my build up. For me, was told it was unburned gas. I run a 180° thermostat in the summer and 195 ° in the spring and fall.
The OP will have to answer on his intake.
 
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