I can't seem to solve this engine problem!

[Guitylerham]

Background:
'66 coupe with 289 2bbl
single vac distributor
manual steering/brakes/no AC
C4

Problem:
About a month ago, my car would start and idea little rough. When I'd put it into gear it bogs down and stalls. When driving away it would hesitate, then surge but once going faster it would drive close to normal (still hesitating at times even at cruising speeds). I drove it longer and the problem went away (I thought it was dirty fuel that cleared itself up). It happened again a week or so later so I used SeaFoam carb cleaner down the carb throat and after plumes of white smoke it cleared up and was fine. Then a few days or a week later, the same problem happened again. That brings us up to a few days ago.

I checked the vacuum pressure and it reads 15-16 (a little low). I sprayed starter fluid around the carb and manifold and didn't find any leaks to my knowledge. I then used a dwell meter and set it to 29 degrees and set the points gap to 0.018in. Then I unplugged the vacuum advance and plugged it and set the timing to 6 BTC. Then I'd plug the vacuum back in and the dwell would drop about 9 degrees and the idle would increase by about 100 rpm's. I was told that dwell should not change when the vac advance was plugged in or removed. So I bought a new distributor and installed/set dwell/gap/timing and the same problem happens. It idles very decently but when I put it in gear, it idles down and I hear a very diesely rattle (I assume coming from the exhaust below, as I sit in the car with my head out the door listening) and it hesitates and lurches forward. People prolly think I'm revving my engine at them trying to show them up when I drive slowly past in the parking lot!
Is it my transmission? I've found that the dipstick is covered in foamy fluid. This may be from when I had my fluids changed, they could have overfilled it. I read where someone also suggested replacing the coil. What do you guys think? Another thing I noticed is that I seat the carb fuel mixture screws and then back them out 1.5 turns, I can screw in the left one all the way and the engine will keep running, but the engine will stumble if I turn in the right screw too much (as to be expected). When you adjust the carb, do you screw in each screw at a time or do both screws have a turn at the same time?

*Should I have the car in gear when I adjust the timing and for that matter the idle speed as well?

 

[StangBanger44]

Mine does the same thing with the screws, still trying to figure that one out. This all started when i rebuilt the carb, i do i need to set the idle higher for when its in gear but not sure if thats the same problem.

 

[10secgoal]

Screw them both completely in. if it doesn't die you have an internal fuel leak.
It sounds like dirty gas to me. See it pretty often. Next time it happens, pull out both idle screws. Shoot in some carb spray and hit it with compressed air. This will dislodge and junk in the idle circuit. If you put the screws back in and it clears up immediately, time to look into a new fuel system.

 

[mustangdave]

Is the torque convertor drain plug aligned with a hole in the flexplate?

 

[jlangholzj]

you could spend $2 and get an in line filter......probally rusty tank. thats what i did

 

[Guitylerham]

I replaced the fuel filter a few days ago and also used that carb cleaner, but I still have issues when in gear. Today I realized something: I am getting about 8 inches of vacuum coming from my TIMED port that goes to the advance on the dizzy. I can push the throttle lever closed with my fingers and the reading goes down to about 1-2 inches. But blipping the throttle returns the reading back up to 8. In the past I added a second return spring because the idle wouldn't return all the way to low idle unless I tapped it shut with my foot when driving. Because I have to use two return springs to return the idle to normal, this makes me think that my throttle plate is warped or obstructed causing a vacuum leak that makes the advance change the timing at idle (which it shouldn't). Could this leak cause the hesitation and poor driving?

 

[D.Hearne]

The throttle shaft bushings are likely worn out. That would cause an idle surge problem. The extra spring only compounds the problem and accellerates the bushing wear. Do yourself a favor and ditch the points and condenser, replace these with any of the electronic conversion kits like Pertronix I or II, Crane's XR-1, etc. That will points/dwell eliminate the points and dwell issues as a cause. You're also retarding the timing too much by using the factory 6*BTDC setting. Set it to 10-14*, you'll see an immediate gain in power. If you decide to replace the carb, either of Holley's 2 bbls will bolt on in place of the Autolite 2100 and the larger of the two will give it a boost in power too. Only thing that has to be changed in swapping these is a minor reroute of the fuel line to accomodate the different carb inlet point and use an inline filter before the carb.

 

[Guitylerham]

Is it possible to fix that bushing issue without paying for a new rebuild or a new carb?

 

[D.Hearne]

Yea, it is possible, but the trick is to find a bushing kit to do it with. Good used Holley 2 bbls will run you less than a hundred bucks on ebay.

 

[Guitylerham]

I've just heard very good things about the Autolites and figured I'd try to stay with that but I will look into the holley's and also that bushing kit.

 

[D.Hearne]

Just me, but I've neverhad good results with Autolite carbs. Holleys may get a bad rep on the net, but they're just as simple as the 2100/4100 Autolites, just as reliable too. All it takes is getting to know them. Last Autolite 2100 I rebuilt had issues with hot starts. Unbolted it, bolted on a used Holley 500 cfm 2 bbl and those issues went away immediately. I bought that 500 used from a Stangnet member, my kid took it out of the box and bolted it on his 77 F100's 400 and it worked perfectly. I just swapped carbs on my 89 Ranger's 5.0 yesterday. I had bought a used 570 Street Avenger Holley on ebay. Took it out, and apart, cleaned it inside, replaced the Powervalve then put it back together. Worked fine soon as I hit the starter. The trick is be patient, only buy carbs that are obviously fairly new. Then replace the powervalve and accellerator pump diaphram(s) these are the only rubber parts, which tend to rupture if allowed to dry out. Also keep clean, moisture free fuel thru it. ALWAYS run at least one inline fuel filter before the carb. Then if it seems the carb gets out of tune, look at the ignition system as the cause, it's rarely the carb that does it. Once you set a Holley, it'll stay that way. The only part that wears before the others are the throttle shaft bushings, heavy springs accellerate that wear.

 

[Guitylerham]

Thanks, D.Hearne for the knowledgable advice. I may go that route actually. I'll see what I can find on ebay and then I may put out a wanted add on here.

And thanks to everyone else for chiming in. I'll let you know what happens after I replace the carburetor to see if that relieves the problem I'm having.