I was just stirring the pot.

@Goody

You said in your original post that the AFR goes lean the closer it gets 4k, but the fuel pressure remains steady all the way through. I'm going to say carb and not just because it's almost the only thing left at this point. lol. It really does sound like fuel starvation. If it were spark it wouldn't go lean and right up where it noses over it would get real choppy like hitting a rev limiter.

Ignition misfires certainly cause lean AFR readings. The cylinders pump pure oxygen ["air"] across the wideband, it's an oxygen sensor, not a fuel sensor.

We'll see here soon, there are only so many things that can cause it. Coil is next, it's newer, but a weak spark could be dropping out, I suppose.

From there I'll rob the rebuilt 600 AFB from the Dart and stick it on there.

After that, I'll find some Tannerite.

Please hurry!

Did you happen to check float drop when you had the carb apart?

Yes, within the 15/16"-1" spec for edelbrock, 7/16" when shut

Fuel pressure does not mean fuel in the bowls. You could be out flowing the needle and seats add that to questionable fuel pressure and there you go.

I understand. The fuel height within the carb is to spec and to the top of the baffles, validated by running the electronic fuel pump then pulling the air horn. In addition the fuel pressure was validated at 5-6psi with a mechanical gauge on the windshield while driving.

I would fine it hard to imagine going from an idle directly to 4000rpm with no load could starve the carb. Perhaps a sustained 2nd/3rd gear pull, but free revving in neutral doesn’t demand much fuel.

I agree, I don’t think it’s fuel, but it might drop the bowls enough to screw around with the air bleeds a/f ratio. I had 5 lbs at the gauge and it would drop to 4 lbs. you would think if you have pressure you should be good, but I needed to increase the needle an seat and increase the fuel supply so the velocity of the fuel into the carb was quick enough not to let the level drop. I truly believe its your tach. The way it goes right to 4000 backs off a hair goes right back to 4000 and repeats. I have seen it before.

I’d be very surprised to find this was a fuel supply related problem.

I’m not 100% convinced it’s not valvetrain, but it certainly appears that area is decent, since the heads and cam have already been successfully run on another motor.

When it comes to troubleshooting electrical stuff, whenever possible I like to start out by swapping out “everything”.

For the ignition, I’d see if you could borrow an old points distributor and coil/ballast resistor, and hot wire it to the battery.
If not, then I’d swap in a “known good” distributor, and hot wire in another box/coil/resistor.

I would use none of what’s on the motor now in the ignition system, including the primary wiring.

All that being said........ disconnecting the tac is too easy to not try that first.

Is your battery good???

It takes 30 seconds to unhook the tach from the negative side of the coil, I've seen a bad tach cause your problem.

What he said

So you'll have no idea where the cam timing and evidently you don't care.

Try and not be offended when I say that you shouldn't assemble engines. For you, or anyone else. Until you learn how to degree a cam, and WHY you do it, every single time.


I can give you reasons why dot to dot is a bad way to do it, but you wouldn't care.


There is no reason EVER to skip the simple process of degreeing a cam. EVER.

Thanks for the feedback.

There actually are good reasons to not degree a cam every single time, but you wouldn't care so why bother.

Let us know when the coil or distributor fix your problem.

Make sure the tabs on the floats that touch the needle and seat are bent correct. People mess with them incorrectly and the float level may look to be correct but is not.

Yeah, don't degree the cam if it's the same cam and the same timing set. That's about it. Other than that, degree the cam. Takes less than 20 minutes.


I've seen name brand [censored] that when used together were 8 degrees off. And that was good, quality parts. They just had tolerance stack up.


Again, you degree the cam every time. Unless it's the same parts. It's not that hard.

I think you are wasting your breath. You can only help those that want to do things the right way.

Right! The factory is degreeing every single engine that comes down the line. Moving the cam 2 degrees changes its peak power band about 50 rpms. So moving it 8 degrees changes it about 200 rpms. You figure 8 degrees advanced or retarded that is a spread of about 400 rpm. Ooh, I can feel the difference already.

Wow. I guess I give some guys more credit than they deserve.