Misc vacuum routing, fast idle cam, and idle air bleed ?'s!

Hi there!

New to the forum, so hope I'm not barraging you with too many things at once! I recently swapped a '62 170 for a '68 200, and am having issues with it idling correctly- running rough/stumbling a bunch at idle, but seems OK at speed. Here are a couple of things that I'm unsure of on this engine...

1) There are two lines coming off of the distributor, one in what I call the "normal" place, at the end of the vacuum advance, and the other coming off the top. I routed the one at the end of the v.a. to the carb, and the other to a vacuum source on the manifold- does that seem correct?

2) This all pertains to the carburetor- I've never seen this carb before-but I'm 99% certain it's a Holley 1940 from looking around on the internet a bit. What is the proper idle air bleed screw setting for this carb? All the way in, then 1, or 1 1/2, or 2 turns?

3) Second carb question pertains to the fast idle cam- for some reason it looks like it's missing a piece, but I'm not sure. Here's a link to a picture http://yfrog.com/1q64ij; does it look like it's all there? I guess I think there should be a screw or something going to the cam, to allow for adjustment.

Thanks for the time, guys!

~Jason

1) The nipple on the side of the vacuum can is for spark retard, and I don't mean that personally.
Just leave it disconnected.

2) The proper setting is the one that pulls the most vacuum at idle, but 1 1/2 turns is a good starting point.

3) I looked at a few diagrams on the net and did not see anything related to that hole.
http://www.carbkitsource.com/tech/Holle ... ey1940.pdf

Thanks for the info! That diagram helps too!

~Jason

Yes, it's all there. And I always tell people to go back and verify top dead centre, and true and accurate base timing before they move on to mess with the carburetion system. Are you 100% positive about your timing yet?

Yup, looks like a 1940 carb. I had a '70 version on my '65 when I bought it. The codes said that is was a Motorcraft replacement carb. So the original must have died along the way and it was a later replacement carb. I personally had very good luck with mine. I rebuilt it and it ran like a champ. I eventually switch carbs when I went to DuraSpark II on my engine. But if I could use that carb with the "newer" dizzy I would. It had great drive-ability and decent performance.

Anyway, do you see the slot in the top of the arm? How the fast idle is set is by inserting a flat bladed screw driver in that slot and *gently* bending the arm fore or aft (with respect to arm travel) to change the fast idle speed. Bend it towards the cam to increase high idle speed...

As for the idle mixture screw, it is best done with a vacuum gauge. The FoMoCo Service Manual calls out to set the idle mixture to highest rpm, but I use highest vacuum reading. And on my car these are two different points. Also, to set the idle mixture it's an iterative approach. The idle mixture influence the idle speed which influences the idle mixture point which.... SO, set the idle mixture screw first: back it out about 1-1/2 turns after it has been "gently" seated to get started. Get the engine warmed up to operating temp. Also disconnect and plug the vac lines to the dizzy. Then adjust the idle speed to your preferred speed or factory spec. Then hook up the vacuum gauge and either screw in or out the idle mixture screw until the highest vac reading is obtained. It will more than likely change the idle speed, so repeat the "idle speed adjustment then idle mixture/vac reading" for a second time. Then I do it all again for a third time and call it good.