Got the new motor started... having problems though...

Hey all,

Long time member, small time poster. This motor has been an ongoing build for a few years now due to money issues, but it's just about done except for some problems which I think might be involved with the carburetor - but this is my first experience with choosing a new carb so I guess you could say I'm relatively new to and might have gotten one that was too big.

So this is a '78 200 with a zero decked block and the head shaved, ported, and polished for ~9.2 compression. Mild Clay Smith low end torque cam. Stock bore.

Transmission is a T5.

I've milled down and converted the head to a 2bbl flange and mounted an Autolite 2100 with a 1.14 venturi off a '66? Or so Galaxie with a 289. I also converted the car to GM HEI. I recurved the advance with the Mr. GASKET 92D spring as described. I only replaced one spring as the guide instructed. Base timing is at a starting point of 10* BTDC. I also used a cable throttle from a 1982 F150 and a 1969 Mustang gas pedal. Movement is smooth and flooring the gas yields WOT as it should.

Now for my problems. My mixture screws really don't give as fine an effect on the idle quality as they should. Right now I have them gently turned all the way in and the car still runs - which should not be happening. Plugs are a surprisingly decent light brown. I can't seem to get the car to want to idle reliably. When I give the throttle a stab the car just bogs. If I slowly rev it then let the throttle close quickly the rpms will continue to rise inconsistently with pedal movement and then slowly fall off. It doesn't drop off quickly like it ought to. I've also test-driven the car once in this condition and it was severely down on power. It also will once in a while pop back through the carb when I rev it, but not constantly. I checked vacuum at a port in my carburetor spacer several weeks ago so my memory may be fuzzy here but I seem to remember it showing a pressure instead of a vacuum and no matter what I tried it stayed that way.

I'm leaning heavily on this being a carburetor issue. Is this thing just plain too big for my little 200? A 1.14 venturi 2100 should flow at around 300 cfm, correct? It's fully rebuilt and seems to be in good operating condition to me. The accelerator pump is working - I can look down the throats and see it squirting fuel when I open the throttle by hand. Throttle response is absolute garbage but fuel mixture seems to be pretty decent. I'm starting to run out of theories outside of just finding a 1.02 2100 and seeing how the car behaves with that on it.

Outside of the carburetor is there any other likely cause that I could investigate?

Thanks guys.

start by adding in some timing, push it to 14 degrees initial.

as for the idling issue, i found when i did the two barrel conversion, though i used an adapter instead of having the head milled, that if i set on idle mixture screw almost closed, about a half turn out from its seat, and then used the other to adjust the mixture i had pretty good success. in your case the first thing i would do is make sure that you are not running with the throttle far enough open to be running on the transition slots as that would make the mixture screws ineffective. to check this out you need to pull the carb and hold the throttle closed and see where the throttle blades rest.

Connect a vacuum gauge to intake manifold vacuum. Not an expert on the timing thing, but initial @ 10 without vacuum advance can't be too far off. connecting the vacuum advance line to the correct place should bump it up depending on current conditions.
Idle screws having no effect with advance working indicates an air leak or excess fuel bleeding in some how. If you can set the idle at about 800 rpm in neutral-slowly move your hand over the carb air intake don't shut it off, just vary the restriction with your hand. If it speeds up, you may have an air leak. If it slows down or kills it's getting too much fuel. At idle look down the top of the carb and see if you can see fuel dribbeling from the boosters indicating too high a float or some problem with the power valve. Note any thing that changes the vacuum reading.
Just was working on a non responding Q jet. tor it all apart cleaned it- new gasgets etc. on reinstalling it found the insulating spacer had gotten deteriorated on the bottom from the heat from the adjacent egr valve and leaked
I'm not an autolite expert, just some things from past general experiences Hopefully some more experience will chime in.
Myway

I guess if you were past the idle slots to maintain an idle, you might see fuel dribbeling from boosters. This still could be either lean or rich, so play restricting inlet air watching vacuum and rpm.
Myway

Lets start with the distributor issues.
The 92D spring kit is for the Duraspark distributors, not the DUI.
The only way to fix your distributor for your engine combination is send it to me to have it properly set up.
14 degrees initial will help, but the main problem is too much centrifugal advance in the distributor.
The ignition system need to be fixed before even thinking about carburation issues which in your case may be very little or none. Bill

It is a DSII distributor. It's just using an HEI module instead of the DSII module.

Great. But how much centrifugal advance are you getting?? You also need an adjustable vacuum advance as a real plus to your combination.
When you installed the one spring what was the centrifugal slot you are using 10,13,17??
Also what octane fuel are you running?

Sounds like my issues with my 66 distributor with a bad vacuum canister. Stumble on acceleration and super slow reaction to pedal changes. Swapping to another off my 69 250 (and adding mechanical advance over the vac only unit) fixed it right up. couldn't drive it very long (popped the driveshaft on the test drive), but it did well on a 2 mile break in.