Surging Idle

[Anonymous]

I bought lbones souped up 200 cid six from him a few months back. Found that the triple carb setup would not fit under my 67 hood, so I put on the Weber DGES from my old 200. We've been unable to sustain an idle under 1200 rpm. The engine surges between 1200 and 1500 rpm when running. Tried adjusting the timing, but either the timing marks are way off, or the cam profile changes timing. My thinking, based on fooling around with V8's is that the harmonic balancer may be old and the outer part has shifted due to the rubber going bad. I'm running a duraspark II dizzy with new ignition module (Wells - Ford replacement).

Plugs are blackened with some gray ash. Need some ideas about where to start. If I remember correctly, Lyle put in a 260 or 270 degree cam with solid lifters and adjustable rocker assembly. I'm trying to contact him to get more info, but ----Help! I'm running a C4 and 1200 rpm is way to fast an idle!

BTW, the Weber sat up for about 3 months. Should I begin here?

 

[66200i6]

With the surging, I would first guess that you have a lean condition.

Two things:
How many turns out are your Idle/Emulsion screws? I would guess you need to up the idle jets if you’re adjustment is any further out than two full turns.

Check to confirm that your throttle plate is in the proper position at idle. If not you are idling in the main circuit. If you are, the flow needed by the higher output engine is greater than the plates will allow for idle. In the past I have had to use the same method Audi uses to adjust proper throttle plate position. That is what the little hole or set of holes in the throttle plate are for. This allows additional flow through the throttle plate so the edge of the throttle plate can be adjusted down into the idle/transition circuit positions.

Good luck, Ric.

 

[Anonymous]

Lyle had triple Carter YF carbs on this engine. I gather that you're thinking that my DGES is running too lean. I do have the idle mixture needles set at 2 turns out from bottom. I'm sure that the throttle plates are partially open at the 1200 rpm setting also, as the idle screw is pretty near screwed in all the way. Lyle had these carbs set so that the center carb operated all the time and the front and rear began to open at about half throttle.

I'm thinking I should clean up the Weber, in case the idle circuits are gummed up. You are suggesting that if that doesn't remedy my situation, then I should try gradual enlargement of the holes in the throttle plate?

 

[66200i6]

From the way you describe it there are already holes in the throttle plates. There is a standard setting for the positioning of the throttle plates in the throttle bore. A dimension from the edge of the throttle plate to the surface of the throttle bore usually defines this setting. This positions the edge of the throttle plate close enough to the face of the throttle bore surface to increase the velocity at the little holes to the idle and transition circuits. Check the documentation on your DGES for the correct setting and confirm before you start enlarging the holes in the throttle plates.

If I remember correctly from last year when I was working with the 32/36, two full turns out is about max for the idle screws. If that were the case I would get the idle jet and air jet combinations correct before making any permanent changes (mods to throttle plate).

Another thought, has this carb been rebuilt? If so confirm that the throttle plates were installed properly. The edges of the throttle plates are beveled where they met the throttle bore surface. Make sure the plates are installed so the beveled face is parallel to the face of the bore. This part is kind of hard to describe without a picture.

Ric.

 

[CobraSix]

YOu said the idle screw is nearly all the way screwed in? Is this on the Weber or the outer triple carbs? If it is on the weber, I think your problem is your throttle plate. If closing the idle mix is doing nothing, then your idle circuit is not controling your RPMS, your transition circuit and main are. Close the throttle plate. There should be a screw that does this. Before you close it, turn the idle mix screw out to 2 full turns from all the way in (or springs compressed).

It sounds like your throttle plate is open. This is the same thing that sent me for loops before I remembered the throttle plate.

Slade

 

[Anonymous]

Spent this afternoon taking the Weber DGAS apart and cleaning everything. Then put in new plugs. Fired it up, but still no idle. Then started tracing every vacuum line and found that my son had left a hose off of the tee from the power brake booster. Reconnected it and wallah!! Idle at 800-900 rpm. This is one bad sounding moter. Lots of lope from the cam, and with the dual open headers, it sure sounds mean. Actually sounds meaner than my 302 in my 68. Thanks again for pointing me in the right direction.