Direct 2bbl running rich

pcoup41

pcoup41

Active member
Hey guys, last fall I did a direct 2bbl conversion on my 200. I dont remember the code on the head but it is a 70's 170 head with the intake hole milled out and classic inlines adapter for an autolite 2bbl. Before this head swap I had my 66 head with the adapter for the 2bbl. The carb is off of a 351W and I had a carb just like it on my last setup. Since I got it running last week it has run great and Iv put about 200 miles or so on it. Now tonight after driving into town and back it started running rough. It wouldn't idle, if I held it at a certain rpm you could tell it was missing, and if accelerate with a load it would miss from about 3500 and higher. If I rev it up in neutral its fine. When I got home I pulled the number one plug and it was black (last night it was a nice golden brown). I was wondering if anyone else had this problem and where I could start to look. Im assuming the only option is the carb but idk what. I am also running the mechanical fuel pump.

On another note, since I have done this swap it seems I have alot more blow bye. It smokes out of my breather and smokes out the tailpipes on start-up and when it is warm (which it has never done before). Not sure why this started all of a sudden but w/e. Does not seem to be smoking enough to foul out a plug.

Thanks for any help
 
Check your Float, needle and seat also the floats level :nod: if your running rich or flooding it will wash down the cylinders :bang: Another sign of Smoking at start up is bad valve seals, guides or both.
 
The head I got rebuilt before I put it on so it shouldnt be guides or seals. Could there be a chance it's ignition? if so what can I do to check? I am still running points. I checked for vacuum leaks with some carb cleaner and everything seams to be good. The mixture screws on the bottom of the carb were out pretty far, so I turned them in and backed them out a turn and a half, took it down the road, and it made no difference. It actually got worse and the new plugs were black again.
 
A points ignition system can work OK if it's not the old LOD type if you have a 1967 (Ca.) or 68 and up point distrib you should be good. Do you have a good spark out your coil? From what your describing sounds more like a carb problem. On Autolite carbs would look at the float level setting and or the float check if its too heavy. also check the needle and seat, power valve and or it's gasket.
 
What is the best way to measure the float level? Do you measure from the bottom of the bowl-up? and what is a good level? I also have the original 66 points distributor.
 
The 66 distributor (LOD) won't work right with your combo unless it's Ca emissions unit that has mechanical advance. Carb float is measured with it upside down so needle is closed or you can measure the wet fuel level on the car with carb top off (engine off of course).
 
Is there anything else it could be besides float, needle, and seat? After running it I pulled the cover off the carb and everything seems to be doing what its supposed to. I didnt measure it but the float seems to be sitting where it always has and the needle and seat are doing their job. Could it be a loose jet or something of that nature?
 
IDK what size they are but the carb tag says D7UEAPA H 8B 4. I just adjusted the float down which really didnt make a difference. It still is running really rich, it wont idle, and misses at full throttle at anything above 3,000rpm. Last night I cleaned the points and replaced the condenser which made it run a little better but after a few miles of driving it got bad again.
 
I believe that is a 1.21 and 351 cfm. Wait for the carb experts, but that sounds a little large for your engine.
 
Even if it is a little big it ran great for hundreds of miles. Also the day before it started running rich the plugs were brown. Just dont know what could have happened between tuesday morning and tuesday night.
 
One is it a stock cam? If not you need a vacuum gage to find vacuum at idle. Another test is to see if the idle feed screws can be turned in all the way in and still idle possibly leaking just a bit if like a 1/32 or so off the seat.
Havent worked on one of the 3 bbl ford carbs for ages. Dont remember the power valve set up off the top of my head.
 
bubba22349":19cfsw0g said:
The 66 distributor (LOD) won't work right with your combo unless it's Ca emissions unit that has mechanical advance. Carb float is measured with it upside down so needle is closed or you can measure the wet fuel level on the car with carb top off (engine off of course).
Click to expand...
This hasn't been mentioned again. It'll never run right with mismatched carb and distributor.
 
I set the float level lower, didnt make a difference. Then I replaced the power valve, now it runs super lean. I found a vacuum leak under the spacer so I fixed that and nothing really changed. Sprayed it with carb cleaner again and I cant find another leak. So now it runs lean, wont idle at all, and when I give it gas it will stay at the new rpm for a while and slowly go down. Unless I pump the throttle again it will die. As for compression I didnt actually test with a gauge, but had a buddy stick his thumb over the spark plug hole. All seemed to have alot of compression and when it is running each header tube gets hot.
 
Too big of a carb will often run lean because the signal is weak. In such cases the jetting in idle main and power curcuits would require changes most of the time richining them up because the weak signal would pull less fuel.
If you still have the factory vacuum only distributor a newer one would work better.
Have to ask did you just slap a 351W 2bbl on a stock engine?
 
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