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The accelerator arm return spring gets connected to the exhuast pipe flange you see in your picture. In mine, there is a hole near the edge of it where the end of the spring hooks into. For a 200 engine with an automatic transmission, the carb has 2 dashpots, and only 1 dashpot for manual transmission applications. The carb with the 2 dashpots will also work well with the manual transmission as well however. The threaded inlet near the bottom of the carb, there has NEVER been anything connected to it for my Mustang ('66 200 engine, manual transmission) and I've owned it since 1976 when my father gave it to me in college.
 

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1966 mustang convertible sprint 200, manual steering and brakes
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Discussion Starter · #22 ·
Thanks for the info. Took it for a ride today with the choke cover reinstalled and choke plate wired open. Definitely nut running rich and rough like it was before so that’s progress. However, while accelerating moderately thru first gear, I’m getting this lunging effect that’s weird. Same thing happens in second however less noticeable. Didn’t feel it in third. Don’t think it’s the clutch slipping because when I floor it (in second at least) the lunging goes away and I accelerate normally. Feels like the air/fuel mix is off. At constant speed, no issues. Is there a way to definitively rule out the clutch ?
 

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1966 mustang convertible sprint 200, manual steering and brakes
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235 Posts
Discussion Starter · #23 ·
More info. That lunging feeling goes away when I get aggressive with the gas pedal. Light to moderate acceleration = lunge/surge. Heavy acceleration behaves as expected. Carb adjustment ?
 

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lean condition on the surge..? just a thought...my son's 200 would have a little "hiccup" in the idle when lean, and sometimes would "lurch" when letting out the clutch and it felt like a 4x4 driving in low 4 wheel drive...

Lean n lurch...I think those terms are in the shop manual....not really!
 

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1966 mustang convertible sprint 200, manual steering and brakes
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235 Posts
Discussion Starter · #25 ·
☺ As far as I understand, the only way to change mixture for mid and wot is by changing jets ? I did see something about adjusting the accelerator pump by bending linkages, not sure if that would help in this instance.
 

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Idle mixture screw can be opened too much and will expose the slot for transition. Fatten up the idle and see if the lurching in first gear goes away….like I said, just a guess, but it worked in my case.
 

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1966 mustang convertible sprint 200, manual steering and brakes
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235 Posts
Discussion Starter · #27 ·
Will try it, thanks
 

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1966 mustang convertible sprint 200, manual steering and brakes
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235 Posts
Discussion Starter · #28 ·
Turned in the idle mix screw a bit and started losing rpm. Think it’s about right. Still kind of a rough idle with a little bit of engine shake. Seems like a vac leak issue ….
 

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Put a vacuum gauge on it and check the timing. If you are timed correctly at the correct rpm, you should have 18-20" of vacuum on a 200. You want the gauge on manifold vacuum.

Have you checked to see if you have a LOM distributor?

Pull the distributor cap off and look at the distributor plate. If you see two springs you have a LOM, if you see one spring you have a 68+ non-LOM distributor.

It is apparent that your engine has been out of the car, who knows what was replaced and it the correct parts were used.
 

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1966 mustang convertible sprint 200, manual steering and brakes
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235 Posts
Discussion Starter · #30 ·
2 springs, pertronics1 and flame thrower 1.5 ohm coil. What makes you think the engines been out of the car ? Just curious. I know the head has been replaced but I think it was done with the engine in. I’ll pull some numbers off the block to see what that tells me.
 

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My 200 was also doing the low load surge thing. Would happen when cruising at any legal speed, worse as I approached 70. To make a long story short, I had over tightened the screws holding the top to the body casting. That distorted the top at the rear so it was no longer flat. I was able to see it by laying a straightedge across the sealing surfaces. The result was air coming into the venturi perpendicular to the desired flow, which introduces turbulence and upsets the fuel pull through the venturi.

The two corners at the back are easily flexed to straighten them out.

Unfortunately I cannot find a torque spec for those screws.
 

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1966 mustang convertible sprint 200, manual steering and brakes
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Discussion Starter · #32 ·
That was some good detective work figuring that one out ! I’ll check mine and see. Maybe I’ll put a smear of silicone (just a temporary fix) around the carb sealing surface and see if performance changes.
 

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1966 mustang convertible sprint 200, manual steering and brakes
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Discussion Starter · #34 ·
Tenacity is a good trait in our business (and hobbies).
 

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Idle mixture screw can be opened too much and will expose the slot for transition. Fatten up the idle and see if the lurching in first gear goes away….like I said, just a guess, but it worked in my case.
Idle SPEED screw will open the throttle plate to expose the transition port (not a slot on Autolites). Idle MIXTURE screw will only regulate the amount of emulsified fuel discharged through the idle discharge port.
 

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The oil pan is not the same color of the engine. Everything is very clean. Little chance that a 55 year old car has the original untouched engine in it. That car was bought to be driven. If it was driven until 1990 @10,000 miles a year, it's got a quarter million miles on it.
 

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I read the installation instructions for an aftermarket electric choke conversion yesterday. Your small vacuum passage for the hot air choke may already be plugged, and will need to be cleared if you want to return to the stock choke. You might have a small lead pellet (or a plug made of some other material) stuffed into the passage where the choke housing and lower carb body join. Probe with a piece of wire to check, or disassemble to be sure.
 

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1966 mustang convertible sprint 200, manual steering and brakes
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Discussion Starter · #39 ·
Thanks Graymare !! I really appreciate that and will check it out. BMC - makes sense. The PO changed out the oil pan just before I bought it (Stripped leaking drain plug). This makes the “new” front and rear pan seals suspect for my oil leak issue. No leaks yesterday idling in the driveway. Will try driving today and check for fresh oil leakage. Thanks woodchuck - how do I impact the midrange acceleration fuel/air ratio? WOT performance seems ok, at least no surging.
 

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1966 mustang convertible sprint 200, manual steering and brakes
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Discussion Starter · #40 ·
We’ll, some progress today. Disassembled, cleaned and replaced the pcv valve along with a new one. The old gasket was as hard as a rock and had shrunk, creating a small vacuum leak between input and the pcv valve. Nice and snug now. Idle still a bit rough as in further vac leak somewhere. I remembered an old trick and started spraying vacuum sealing points with carb cleaner (Provides a temporary seal and you can hear a change in engine rpm). First thing I sprayed was the gasket between carb and intake - rpm’s changed significantly and idle smoothed right out. 😁. Off to get a new carb gasket tomorrow. Probably buy the rebuild kit since a few other spots has some gas seepage. Gotta love progress. Tomorrow the valve cover comes off and we’ll see what surprises await underneath. If my luck holds, the rest of that pcv retaining ring will be stuck in the sludge waiting for me.
 
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