Something weird going on

[cudabob496]

It was all by spark plug color, very rough indeed. After many hours of carb tuning, it's easy to see why EFI was needed when you realize that you are the ECM.

I considered EFI lately, due to my carb problems. And I just considered buying a whole
new carb. But now that I can fairly easily tear down and rebuild the carb, and realizing they are not that complicated, and along
with AFR, EFI doesn't seem to be a necessity now.

Probably a lot of people have struggled with a carb, given up, and bought a new one, or
gone to EFI, when their carb may have only needed a simple fix. In my case,
a $5 gasket!

[734406pk]

I considered EFI lately, due to my carb problems. And I just considered buying a whole
new carb. But now that I can fairly easily tear down and rebuild the carb, and realizing they are not that complicated, and along
with AFR, EFI doesn't seem to be a necessity now.

Probably a lot of people have struggled with a carb, given up, and bought a new one, or
gone to EFI, when their carb may have only needed a simple fix. In my case,
a $5 gasket!

I guess if you had to pay for technical labor to diagnose/repair/tune the carburetor, it would have been cheaper to get a new carb or even switch to an aftermarket EFI system. Holley DP carburetors haven't changed much over the years and parts are readily available (and copied). Aftermarket EFI on the other hand may work well when it works, but if you have a drivability issue five years later, you could easily be on your own. The Holley design will still be there.

[cudabob496]

dang, went to 81/86 jets, but cruising at 2500 rpm still gives 16 on AFR meter.
When floor it to 4 or 5000 rpm, AFR drops to 12 to 13.
timing was too advanced,and reset to 36 total, but still 16 on AFR.
not using my ram air box right now, and just have 4in x 14 inch K&N with K&N lid.
Also have Hilborne scoop forcing air on top of K&N lid.
Maybe engine not use to all this air.
O2 sensor seems secure in exhaust pipe.
Hopefully not an intake manifold leak.
will see if 83/86 makes any diff I guess?
it is quite cold out, in the 40's.
Holley said 16 not a big deal, if engine running well.

[Strawdawg]

There is nothing wrong with 16-1 a/f if the car does not stumble upon light acceleration.  Just gives you better gas mileage at the sake of slightly more emissions.

Trying to tune cruise a/f with main jets is often the wrong approach.  Changing the air bleeds would be the better approach.

Air is much more dense on a cold day than a warm day so it is natural for the a/f to be considerably leaner.

This answers your comments above as to why wide band driven F.I. is desirable   Particularly if one tends to obsess about such things.

[734406pk]

dang, went to 81/86 jets, but cruising at 2500 rpm still gives 16 on AFR meter.
When floor it to 4 or 5000 rpm, AFR drops to 12 to 13.
timing was too advanced,and reset to 36 total, but still 16 on AFR.
not using my ram air box right now, and just have 4in x 14 inch K&N with K&N lid.
Also have Hilborne scoop forcing air on top of K&N lid.
Maybe engine not use to all this air.
O2 sensor seems secure in exhaust pipe.
Hopefully not an intake manifold leak.
will see if 83/86 makes any diff I guess?
it is quite cold out, in the 40's.
Holley said 16 not a big deal, if engine running well.

You are likely running off of the transition slot circuit at cruise (just off idle). This circuit is unfortunately fixed (slot) and not adjustable with stock metering blocks. The idle circuit will contribute fuel here so if you turn out each mixture screw say 1/8 turn or maybe less, you should see a slightly richer AFR at idle and slightly above idle (light cruise). The air bleeds are fixed too so thats about all you can do with out buying a new Ultra XP , HP or similar AND adjustable metering blocks.

https://www.holley.com/products/fuel_systems/carburetors/hp/street_hp/parts/0-82851SA
https://www.summitracing.com/parts/qft-34-105qft/overview/

 I would recommend installing the cold air intake etc that you will be running with first and see how that effects your AFR.  16:1 AFR at light cruise is not a bad thing as long as the engine likes it. 12-13 on acceleration is OK too. Check your plug color soon just to see if the heat range is correct.

[cudabob496]

You are likely running off of the transition slot circuit at cruise (just off idle). This circuit is unfortunately fixed (slot) and not adjustable with stock metering blocks. The idle circuit will contribute fuel here so if you turn out each mixture screw say 1/8 turn or maybe less, you should see a slightly richer AFR at idle and slightly above idle (light cruise). The air bleeds are fixed too so thats about all you can do with out buying a new Ultra XP , HP or similar AND adjustable metering blocks.

https://www.holley.com/products/fuel_systems/carburetors/hp/street_hp/parts/0-82851SA
https://www.summitracing.com/parts/qft-34-105qft/overview/

 I would recommend installing the cold air intake etc that you will be running with first and see how that effects your AFR.  16:1 AFR at light cruise is not a bad thing as long as the engine likes it. 12-13 on acceleration is OK too. Check your plug color soon just to see if the heat range is correct.

ya, Holley said look at plugs as well.
Engine seems to be happy.
Ram air box will definitely go back on this summer.
So the 4 corner idle screws determine fuel delivery in the carb, not air?

[HP_Cuda]

Some interesting info for ya Bob:
http://www.junkyardgenius.com/holley/tune01.html

But the screws are just for idle. They allow you to adjust the amount of fuel at idle which is done by using a vacuum guage to gain the highest vacuum reading.

[cudabob496]

well, this is weird.
took it out, and it ran perfect.
before taking out, opened up all 4 corner idle screws
1/4 turn, so all out 1 and 1/2 turns.

Now, cruising at 2500 rpm, AFR 14.5 to 15.

Everything seemed to be working and performing perfectly.
Obviously going 36 degrees total helped.
And for the first time, the large wire I have going from my alternator to an amp gauge, to the starter solenoid,
was steady at 10 amps, while cruising. Never been steady, always fluctuated, but I think the rerouting of some
engine bay wires may have done it.

I even have the QA1 adjustable shocks dialed in for a very smooth ride.

So, will enjoy "perfection" for a while, until something else comes up, which it always does.

One car I was glad didn't challenge me today. New Z06 Vette. 650 hp and 650 torque.
Of course I would not have backed down, but may have increased my odds of dying or
going to jail, had we raced.

[cudabob496]

I think with an AFR meter, we can adjust the 4 corner idle screws
and get pretty close, without doing the vacuum thing, which is a pain
for me with my cam.

[734406pk]

So the 4 corner idle screws determine fuel delivery in the carb, not air?

Fuel and air (from the air bleeds) emulsion (increases fuel atomization). The air bleeds also prevent the fuel from siphoning out of the float bowls when you shut off the engine. When you turn the idle mixture screws out, the AFR will move toward rich.

[70chall440]

glad you got it sorted.

[734406pk]

 Check this out:: Gunson's "Colortune".

https://www.youtube.com/watch?v=_49yYvPsHPI

https://www.amazon.com/Colortune-for-14mm-Spark-Plug/dp/B000E9VGNM

[cudabob496]

Check this out:: Gunson's "Colortune".

https://www.youtube.com/watch?v=_49yYvPsHPI

https://www.amazon.com/Colortune-for-14mm-Spark-Plug/dp/B000E9VGNM

Pretty cool, and cheaper than an AFR meter, though not as precise.

[cudabob496]

One thing I am not doing, though its recommended, is having a tiny
bit of the transition slots open/exposed on the secondaries.
That might up my AFR at idle a little bit?

[734406pk]

One thing I am not doing, though its recommended, is having a tiny
bit of the transition slots open/exposed on the secondaries.
That might up my AFR at idle a little bit?

 Yes, that is recommended for best performance but if you open the secondary throttle blades a bit, the curb idle speed will increase, so you will have to decrease the throttle opening on the primary side to compensate. IMO, a gain in air/fuel from the sec. side be cancelled out by the reduced air/fuel supply on the primary producing the same AFR (?).This is just theory, so there is only one way to find out. Record your baseline so you can return to the original setting if needed.