200 Tuning help needed

The set up: stock 200 long block, rebuilt 1904 Holley, DSII @15 degrees base timing, plugs were gapped at just under 040, MSD coil and 6A ignition. I had it running ok but with a high idle, then 20 miles later I couldnt get it started. Pulled the plugs and they are showing that it was rich as can be. So on the 1904 carb, where there is no fuel air mixture screw, do I drop a few sizes in the main jet or what? My only other thought is a vacuum leak keeping the power valve open but I kind of dont think so. Any thoughts?

Oh and Im a complete carb novice so keep it simple lol

My situation is a little different but I will try to be helpful at least.

The 200 in my 1964 Mercury Comet has a Holley 1940 with the Spark Control Valve. In the long run, I ended up putting in a DUI distributor that seems to work really well. This required me to switch from the SCV to manifold vacuum. No big deal. It also means that the original 12 degrees of timing called for in my manual is bogus and I've been fine tuning the timing using a combination of a vacuum gauge and how it runs down the highway.

Why is this important to you? Does your Holley 1904 have a Spark Control Valve and is it functioning at all much less properly? Does your DSII/MSD ignition require some change in the timing setting? What kind of vacuum is the engine pulling? And just as importantly, is the reading being made at normal operating temperature? (I know this is kinda basic but feel it has to be thrown out there.)

Something else I found while digging around for information about the 200 is that some people have had trouble with the harmonic balancer slipping. I don't necessarily believe this because I thought they were keyed to the crankshaft, but, are you truly getting the 15 degrees on your timing marks? This would be most obvious according to the reading on a vacuum gauge.

It's not much but these are a few things for you to chew on.

The balancer can slip..The hub is keyed but the outer part where the timing marks are, is mounted to the hub with rubber...That is what dampens the harmonics of the crank and it can slip.

You can increase your plug gap to .045"-.048" with your ignition. I believed i recurved the DS11 a while back.
See if you can get an A/F tester so you can see what your carb is producing.

Hi, it sounds like the engine is flooding. You mentioned a rebuilt carb. Did you change carbs, or rebuild the old one?
I would check the needle and seat for dirt, and check the float level.
I would make sure the choke is fully opened.
As mentioned, with electronic ignition, open up the gap. Good luck

I love the 1904 man. I got one off a '53 215 or 223 L6. They're super easy to rebuild, I've done like 4.

One thing to make sure is that yoy get the right length for the accelerator pump. Theres a long and short one, if you get the wrong one, it'll always hesitate or not work properly. Thats the piece on the passenger side that has a pushrod that comes out and a little cam hits in when you work the throttle.

2nd, you say there is no idle mixture screw? That's not good, it needs one. It should be on the base where it meets the engine intake. It will come up at an angle somwhere at the front i think.

Check that the choke is opening. These have mechanical chokes unless its a 1908, then it has a hot air choke. Or its some spooky rare 1904. A mechanical choke means yoy manually have to open and close it. If there is not a cable coming from the carb, and there isnt some buldging black thing at the back of it, then you're choke isn't being controlled by anything. NAPA sells a choke cable, or yoy can permanently set it at open and you just have to keep your foot on the gas when its cold to keep it from stalling.

Idle adjustment is at the back of the carb, it rides the cam connected to the choke. I used to have mine idle around 550. It was beautiful.

The guts of it are pretty simple, it has one big piece that acts like a brain box for the carb. Make sure it is all clean. There are a couple of check balls, they get stuck if they sit for a while. If they are, try to get them unstuck. Also, literally everything on this carb warps easily, so be careful. The brain box thing tends to warp from overtightneing and so does the bowl.

The brain box can be filed smooth and reseal with no problems. The bowl will take heating, a vice and some wood.

If you want a very detailed rebuild tutorial, Mikes Carburetors does a wonderful job of that. If you find the markjngs on the bowl, where the fuel line goes in, theres a flat area that says a number. That will tell you what it was intended for and what rebuild kit you'll need.

Good luck man!!

I thought that might B a 1904. How to ID 1920 / 1908 / 1960 from 1904?
Thnx Ryan.

Don't 4 get ign tune comes B4 carb...
but sounds like its "all set" & ur onto carb (just a double ck frm me sefus...

It has to have an idle mixture screw. If you look at the picture above you can see it right there on the left near the base.

chad":150acem4 said:

I thought that might B a 1904. How to ID 1920 / 1908 / 1960 from 1904?
Thnx Ryan.

Don't 4 get ign tune comes B4 carb...
but sounds like its "all set" & ur onto carb (just a double ck frm me sefus...

Click to expand...

The 1920 is very similar to the 1904 but the funnel at the top of the carb is taller and i havent seen them on things other than Dodge. But I really only have experience with the 1904 and 1908. AMC might run the 1920 as well.

The 1908 has a smaller venturi as well since it was made for the 144 and 170. They also usually have a hot air choke.

I know nothing about the 1960.

Here are some other 1908 shots

The 1904 too also usually has a different choke butterfly than the 1908. See both pics

any glass bowl is OK by me.
(long as it fits an i6/slanty/stove bolt/etc).
Thnx, I'll study what U left us.
Cont success, lill Bro. Very, very good 2 C ur advancement as trouble shooter & young mechanic !!!

chad":30pjljl6 said:

any glass bowl is OK by me.
(long as it fits an i6/slanty/stove bolt/etc).
Thnx, I'll study what U left us.
Cont success, lill Bro. Very, very good 2 C ur advancement as trouble shooter & young mechanic !!!

Click to expand...

I got 2 of these glass bowls, only need 1 more! I love them. Fun little carbs. Thanks man!