Progress Thread The next "big" project for my Cobra

[LILCBRA]

Just for understanding: did you just check AFR with the Mustang in P or N? Jet size should not have influence on the idle mixture. Idle mixture should only react to idle mixture screw settings.
Main jet size can only be checked, when you are cruising...

In neutral (I have a 5 speed). I'll drive it and post a video at some point. I just figured I'd give it a rev and hold for a minute to see what the AF guage said and adjust a little if it would still hit the 12s. It would, so I took it down 2 sizes. I was able to get an idle mixture that read really lean for a little bit - like in the 16s-17s, but adjusting the mixture screws to vacuum took care of that. It now maintains vacuum at idle around 14-15 inches even if the AF gauge reads a little rich. I'm not sure why the idle mixture jumped like that after a jet change - I was just trying to bump the mixture at a higher RPM....

But on a positive note, there is absolutely no stumble when bumping the throttle - it reacts almost instantaneously.

 

[LILCBRA]

Took it out for a short drive a little bit ago. I think the jets might be a little lean, but they're real close. And I think I may need to play with discharge nozzle sizes now. At cruise the AF seems to be pretty good, but when I step on the accelerator, like if I was trying to pass or something, it would read pretty lean. I'll try to get the video edited a little later and upload a short part of the drive....

But here are a couple pics from my new phone after I got home and parked. Thats a 14.5.

 

[LILCBRA]

And some of the video. I really need to find a microphone that would be compatible with this camera that works well for a loud environment. So, until I do, most all of these videos will have to have no audio.

 

[extra_stout]

Without audio it's difficult to "hear" if you are accelerating or not and so on.
I think you need a blue cam in 1 (or 2) to solve your accelerating lean condition:

It's important with a double pumper to get a lot of fuel trough the acc circuit before the secondaries and/or the power valve opens. This means you need the right cam (like the blue) and a bigger nozzle helps too. But cam is more important.
Regarding main jet size: I think it looks pretty good, if the lean condition is, when you go of the gas pedal, which I think is happening in the video at 2:50 when you change gears (?): at least RPM drops and you get lean condition. Getting lean when going of the throttle is not a real problem (beside the AFR reading is not accurate at low gas flow).

 

[extra_stout]

You have a very nice piece of engineering on top of your engine. Especially with manual transmission you will have a very good running car, when done tuning such a complicated carb.

 

[LILCBRA]

Thanks for the suggestion of the blue cam! I went ahead and ordered a cam kit, it should arrive tomorrow. That's something I don't think I mentioned earlier, but it was a thought. I'm also wondering about the secondary cam but figure getting the primary side worked out is my primary goal. (I'm pretty punny, huh? lol)

I've also had this thought - what do you think? I was thinking of removing the secondary actuating arm and just concentrating on the primaries for now. That way I know that the secondaries aren't doing anything to skew the numbers that I'm getting from the AF gauge.

And I've also done some research on adding an external microphone to my camera. I've found that my camera doesn't support one. But you're right, it's easier to diagnose when you can hear it, too. So I'll turn the microphone back on and see if there are any settings on the camera that I can play with concerning noise reduction. It's either that or I've thought of maybe just covering the mic with a cotton ball somehow - maybe that would help?

 

[extra_stout]

Thanks for the suggestion of the blue cam! I went ahead and ordered a cam kit, it should arrive tomorrow. That's something I don't think I mentioned earlier, but it was a thought. I'm also wondering about the secondary cam but figure getting the primary side worked out is my primary goal. (I'm pretty punny, huh? lol)

I've also had this thought - what do you think? I was thinking of removing the secondary actuating arm and just concentrating on the primaries for now. That way I know that the secondaries aren't doing anything to skew the numbers that I'm getting from the AF gauge.

I also have a 4777 on my engine. I can feel at the gas pedal, when the secondarys starts to open, because of the higher effort. This was enough to me, to tune the primary acc circuit. Also if vaccuum drops below 7.5, power valve comes in...
So you should accelerator in a way, that the power valve and the secondarys stay closed, if you want to tune for the the right primary acc pump cam.
Removing the secondary throttle actuating arm is possible as far as I know. But don't remove the secondary actuating arm of the acc pump!
Secondary pump cam is not that important, because than power valve should already be open and the 4777 adds more fuel than a standard carby trough the power valve circuit. I run pink in 1 on my 4777 as a secondary pump cam. But probably I could remove the secondary side acc pump completely; at least with my engine, that has lower HP numbers than yours.

And I've also done some research on adding an external microphone to my camera. I've found that my camera doesn't support one. But you're right, it's easier to diagnose when you can hear it, too. So I'll turn the microphone back on and see if there are any settings on the camera that I can play with concerning noise reduction. It's either that or I've thought of maybe just covering the mic with a cotton ball somehow - maybe that would help?

I like your idea to use cotton. And if thats still to loud add duct tape:

 

[LILCBRA]

I also have a 4777 on my engine. I can feel at the gas pedal, when the secondarys starts to open, because of the higher effort.

Meaning you can physically feel the effort of the springs on the shafts open? I can't feel that much, but that's also my bad foot. I also have a secondary return spring which makes the pedal stiffer.

 

[extra_stout]

Meaning you can physically feel the effort of the springs on the shafts open?

Yes, I feel that. At least I think i do. I had also the secondary throttle blades and shaft removed, because I installed new bushings. And it could be that, the torsional spring at the shaft has more preload, than original...

 

[LILCBRA]

I don't know why I didn't think of this when I was dealing with the dash and gauges a few weeks ago, but I think I'm going to see about swapping the volt gauge and the AF gauge locations. That way you can see the vacuum and the AF ratio at the same time, especially in a video link.

 

[LILCBRA]

Something I keep thinking about: I understand the pump cam mechanics, but the fluid dynamics kind of has me thinking more. While the blue cam would produce more pressure earlier and shoot fuel through a smaller nozzle for a slightly longer duration, a larger nozzle would supply more fuel at a faster rate at the same RPM level.

But, on the other hand, less pressure through a larger orifice might cause the fuel to dribble vs shooting a stream as would be more optimum....

I guess what I'm trying to say is that I think that maybe I should try both the blue cam AND a larger nozzle. Since I only have 35s, that's what I'll try. In any event, I think it'll raise the AF ratio at part throttle acceleration - hopefully it'll be just what the doctor ordered!

 

[LILCBRA]

I was wrong on the nozzle sizes - I have a 32, not 35. But I went ahead and swapped that in last night and took it for a drive. I shot video with sound again and I'll upload that later, but I'm still having a lean problem with slight acceleration. I had a chance to hold the accelerator while accelerating for a little bit and it never richened up - like after the accelerator pump shot should've been expended. That got me to thinking that maybe I need a bigger power valve? Or something in that circuit needs attention? Will have to dig into some research about that.

But here's a night pic I took with my new phone. It looks really good in the dark!

 

[LILCBRA]

Just took it for another drive and watched the vacuum gage while mildly accelerating and keeping steady rpms. I don't think the power valve has much to do with it now. If it does, I'll probably need the biggest one since vacuum stayed above 10. Thinking the jets are too lean and the idle circuit is compensating at lower rpms. Took video with this too....

 

[LILCBRA]

Got this minute long video that kinda shows what I ran into.



But since I think the jets are way too lean, I decided to start from scratch again and reinstalled the original jet sizes. I took it for a short drive afterward and had rich conditions again. I also shot video of that but haven't looked at it yet - the car started acting up on me shortly after leaving the house, so I turned around and took it back home and haven't done much with it since. I ended up taking the rest of the weekend and started working on the house again since it needs to be finished.

To be continued....

 

[extra_stout]

But since I think the jets are way too lean, I decided to start from scratch again and reinstalled the original jet sizes.

That's the save way to do it!

 

[2Blue2]

Wrong!
Do it Again!

 

[LILCBRA]

Been waiting for Stumpy's subframe connectors for a while, mainly due to my mistake. But now that they're on their way it really seems that someone at UPS is lost....

 

[2Blue2]

ring around the country?!?

 

[Noobz347]

They just keep passing it around until it reaches a facility that is looted by underprivileged thugs.

It will eventually disappear in St. Luis, Chicago, LA, or NY.

 

[LILCBRA]

I might get it today.