Idle quality on 200 inch six

[JackFish]

I'd be happy if my engine could idle smoothly at 700rpm.
I attribute the problem in my case to poor fuel atomization.
The problem gets accentuated with a performance cam.
You have to tweak the idle circuits a fair bit.

 

[63falcon4drwagon]

 

[72maverick]

Don't know if this will help but my first engine was a little rough. Added a weber carb, electronic ignition, wires, spark plugs,... standard tune up. Ran smooth. With the engine rebuilt, it idles really smooth once it warms up

 

[hotroady]

I finally got around to doing the autolite 1100 SCV mod. I just used JB Weld marine epoxy to plug indicated vac holes. I now idle below
500 rpms in gear.

I have a 65 Mustang 200. Pertronix ign., Duraspark dist. Recurved, Crane 91 LX hi current coil, MSD 6A box. .050 gap on Autolite plugs.
600 RPM was as low an idle as I could attain. The conversion wasn't truly finished until I sealed those vac leaks in the 1100. I removed the choke for better breathing. Converted back to ported vac, as I was running engine non ported to dist, before. This combo is a large step upward in driveabilty!

 

[hotroady]

Keep the LOM carb and swap to a Ford DS1 distributor that triggers either a GM HEI (standard 4-pin), a Ford DS box, an MSD, or just about any other electronic box. Just plug the carb's LOM port and run the distributor vacuum to the manifold.

That's what I had, but not quite so. I just plugged the LOM port before, and ran manifold unported vac.
Ported vac gives a reference point to the tune. I have about 15* initial advance. I modded the advance arm to limit full advance, in order to increase initial safely, on 87 octane unleaded pump gas.

 

[xctasy]

...does this old engine just not idle that smooth?
I have a '56 Jag with an inline six that will idle dead smooth @ 500 rpm all day long...

Thanks for your time and thoughts.

-greg

"How high it needs to be to clear the valve cover":
One and one half inch with a shorter Idle adjustment screw.
The throttle and choke screws are what hit the valve cover.
I can now shift into high at 70mph jump up to 85 then slow down.
It has much more full throttle higher rpm power than my Carter YFA.

I would not mill the log!
This log carb opening area is larger area of both throttle bores of a BBD.
The BBD venturi is smaller than the bore size. Make it simple.

[/quote]


63falcon4drwagon is the poster child for making a smooth idling I6 by adding another venturi (Ball and Ball BBD Carter 2-bbl) and cleaning up the short turn radius.

In my experience, no in line six idles well unless it has a two corner idle. Some versions of the 32/36, and most 5200 Holley Weber workalike carbs do.

Both legs of the log need to be free of the influence of the other.

See viewtopic.php?f=1&t=79820&p=618156#p618156

In addition, his work on the SCV idle drillings has been copied by me many times