My Six Pack seems odd

[440beep]

Engine is a 512 with aluminum heads, 10.5 CR. Initial timing is 20 and all in at 2,200 is 36. At idle, Six Pack hovers around 14.5 AFR. But while calmly cruising at 35/40mph, the AFRs are 12.5 driver side and 11.5 pass side, or richer. Center carb has 62 jets and 3.5 PV. secondaries are jetted 80/78 driver/pass sides with black springs. WOT and acceleration AFRs are in safe range 12.5-13.5. It’s the calm cruising AFRs that annoy me and I’m going to jet down the center carb to 60 and see what happens. But this seems so odd from the normal 440 engine settings of like 64 center jets and secondaries might be richer too. Therefore I’m struggling to make sense of my bigger cubic inch engine needing to be jetted down compared to a 440.

When cruising, I’m assuming the secondaries are not opening, but are they still contributing fuel via idle circuit? And it’s odd that the pass side AFR is richer especially if only running on center carb. I have the Innovative dual AFR setup so can read both banks.

Any thoughts of what I’m missing or not thinking about? But maybe the saying “tune for your engine and every engine is different” is what’s happening here.

 

[dan juhasz]

Mine is not stroked and I only have an o2 on one bank but I have similar results. When I tried smaller jetting on the center all I accomplished was to create a lean surge. So interested to see what feedback you receive.

 

[Don selleck]

 

[WileE]

First, check all your float levels.

 

[Mopar Miki]

How many turn out are the ctr carb idle mixture screws? should be between 1-1.5
How many turns out is the center carb throttle plate adj screw? 2 turns from zero gives 0.040 on the slot
Is there a 195 degree thermostat? This is must.
Does the car start on it's own after a hot soak? It should
Does it start really easy cold? It should do that too
Does the idle have an even cadence to the sound and not dropping a cylinder? ?
How many turns out are the outboards idler mixture screws? There is a range of adjustment here that affects the cruise mode. There is a balance betwix all that needs to be achieved
A numeric digital display tach is a good diagnostic tool
what is the idle rpm? Automatic? Stall rpm? Cruise rpm?
62 jets should be fine
Are the float levels correct?
Fuel pump? Carter street pump
Does the car "hit" when the secondaries open? If all is well the hit is very hard - that is why six paks rule, go get that hemi....

 

[R413]

195 thermostat is not a must, it can run fine at 180, 170, or 160. it's all in the set up amd tune.

How old are these carbs? How long since they were rebuilt?
Do you have a vacuum leak? Do the outboards close all the way every time?
What are the cam specs and idle vacuum? What is idle speed?
What is Cruz in RPM when the problem numbers come up?
What rear end gears? Is this engine lugging or screaming?
Do you have a power valve? What number?
Where are the O2 bungs welded in, how far from the heads? Headers or manifolds?

Many unanswered questions.

 

[1 Wild R/T]

Any chance the power valve channel restrictions have been opened up? Also what's the valve at cruise vs the P/V number...

 

[440beep]

Running a 180 tstat. 3.5 PV (in original post) TTI 2” headers. O2 bungs are just after header collector. Idle vacuum is 12ish, but when putting in gear, idle vacuum dropped to 7 custom grind cam will get specs tonight. Cruising vacuum is roughly 15. Center carb is new from a couple years ago and NO alterations by me. Rear secondary, with Promax billet throttle plate, was just rebuilt by Woodruff. Not hearing a vacuum leak, and idle RPM is 950. Center carb throttle plate is open just enough to form a square on the slot. Secondary plates are fully closed and I constantly check that. Of course the float levels are right at site openings. 727 trans with 3500 stall.

My center carb mixture screws, if I remember are out maybe 2 turns, and secondaries are out over a turn or else I’m turning the center carb screws out like three turns. I figured turn secondaries out more so I’m not turning center so much. RPMs do drop when I cover secondary idle bleeds so there’s the richness. I have a digital tach in my timing light and tune using that and how I tell RPMs drop when covering idle bleeds.

Really curious if I’m shooting myself in the foot with the secondary idle mixture screws open so much.

 

[Mopar Miki]

Try again on the operating temp , if a 195 t stat is not run - no matter how good the tune up - raw gas collects in the intake manifold and eventually burns off ping ponging the air fuel. Instrumentation does not lie, multiple cars, multiple configurations all show the same data. Argue with the data

 

[8formulas]

When I purchased my car 9 years ago, it had a 160 thermostat in it. It ran great but I let everyone make me believe that I should have a 195 in it because "that's what it's supposed to have". So stupid me put a 195 stat in. That lasted 2 miles. Holy sh*t that thing puked it guts all over the street and boiled the fuel out of the carbs. So glad I made it back home that day. Let it cool down and a 180 (Robert Shaw) thermostat went in. NOPE!!! She did NOT like 180 either. Let it cool down again and went back to the 160 (Robert Shaw). She couldn't be happier. So with all that said, I don't agree that "195 is a must". If you know you're bone stock, then yes, follow the book on tuning. If you're modified, like the OP is, (and me too) you need to tune according to your mods.

 

[DanielSlocum]

T stat only effects minimum coolant temp. It does nothing to effect how hot the coolant will get unless it fails to open when its supposed to.
In other words....running a 160 will not prevent higher temps when stuck in traffic,driving in parades,or hot lapping at the drag strip. It only insures that the temp will reach 160.

 

[Bird 426]

I have a similar problem with my 418 SB.
Every time that I have found something, I haven't. I keep records every time I change something. I am always rich somewhere. I start to nose over with anything leaner than 66's in the center carb. Have tried several different pv's. Carter fuel pump, regulator at 5 psi. Have tried metering plates and currently have Promax plates in. Engine ran great right off the start, hit like a freight train, then, somewhere along it developed a bog. Never have gotten it to go away. I realize, you can only do so much here arm chair quarterbacking.
I'll be watching! I continue to look for answers.

 

[440beep]

Think I’m going to start over with the idle mixture screws and lean out the secondaries as that may be my problem cruising. My Carter fuel pump is also putting out 5, 5.5ish.

Car doesn’t bog at all, it’s just the shitty AFR at mellow cruising that’s annoying me.

I have a similar problem with my 418 SB.
Every time that I have found something, I haven't. I keep records every time I change something. I am always rich somewhere. I start to nose over with anything leaner than 66's in the center carb. Have tried several different pv's. Carter fuel pump, regulator at 5 psi. Have tried metering plates and currently have Promax plates in. Engine ran great right off the start, hit like a freight train, then, somewhere along it developed a bog. Never have gotten it to go away. I realize, you can only do so much here arm chair quarterbacking.
I'll be watching! I continue to look for answers.

 

[Bird 426]

For me, everything changed with cutting the fuel pressure down from 7.5. It can be difficult here to go over everything.
Right now I have
Front carb 72/71
Rear carb 72/71
Center 67/66
PV. 6.5. with 15 in manifold pressure
Purple diaphragm spring
My AFR's are upper 13's at cruise, 2,000 rpm, timing all in at 34. NGK BKRE5 plugs. FBO Ignition. Engine starts and runs great, I'm still rich somehow. OX sensors are placed correctly. It's fall here, so it's cool. Not far from you, over by Rock Island, Illinois, 180 mi.

 

[dan juhasz]

For me, everything changed with cutting the fuel pressure down from 7.5. It can be difficult here to go over everything.
Right now I have
Front carb 72/71
Rear carb 72/71
Center 67/66
PV. 6.5. with 15 in manifold pressure
Purple diaphragm spring
My AFR's are upper 13's at cruise, 2,000 rpm, timing all in at 34. NGK BKRE5 plugs. FBO Ignition. Engine starts and runs great, I'm still rich somehow. OX sensors are placed correctly. It's fall here, so it's cool. Not far from you, over by Rock Island, Illinois, 180 mi.

I use the promax plates also, your 72/71, 2 questions, is the orientation driver/passenger and do the numbers represent holley jet numbers or actual jet diameter in thousands of an inch, ie 72 do you mean .072 thousnads or #72 jet

 

[68-500]

Switch o2 sensors side to side to verify calibration.
Bigger engine sucks harder on carbs therefore smaller jetting.

 

[Bird 426]

Yes, driver/pass. Holley #72 main jet.
I have enough harness to try switching sides on the AFR's. Just replaced the driver's side, fouled. Can these sensors be cleaned? Carb cleaner and a propane torch? Might try that. Just ordered 3 of them.

 

[440beep]

Bird 426 check your PMs please.

 

[Bird 426]

Nothing showing up. Been out all day. If you got my phone number and my pm to you call me. I'm up late. Retired, you know!.

 

[Some Car Guy]

T stat only effects minimum coolant temp. It does nothing to effect how hot the coolant will get unless it fails to open when its supposed to.
In other words....running a 160 will not prevent higher temps when stuck in traffic,driving in parades,or hot lapping at the drag strip. It only insures that the temp will reach 160.

Depends on when it fully opens. That and the capability of the system determine what it will run at in a given ambient temp. I can tell you for a fact a 180 runs cooler that a 195 in my 440.