Odd Problems - Suggestions?

[Hijinx]

OK, I am working a few odd problems. I had to put a new carb on this week, a Demon. I love the carb, expect an article soon. However, I cant get it leaned out and I do not think its the carb. Let me state that its running great. Here are my issues;

I am having to run the mixture a little rich to keep it from stumbling off idle, causing a bit of black smoke. To keep idle down, I have the idle set screw backed all the way out and have idle working through the corner mixture screws. I also have my timing advanced all the way off the scale, almost to the point of being in line with the water pump to keep it from backfiring through the carb. Have to keep timing this advanced to get it started easily.

I feel like I'm missing something big and cant figure it out. Any ideas?

 

[wolf_walker]

On the timing, could you be a tooth off on the distributer?

Carb. The stumbling, how is the accelerator pump set up on that thing, that's usually the place to look for off-idle problems.
The throttle is completly closed and it's idleing at the correct speed? That's odd, vacume leak? It should not run with the throttle completly closed, unless there's something special about the carb.

 

[Hijinx]

I'll check the acc. pump. I may need to bend the lever a bit where it contacts the cam. I've got almost no play and I should have some. Yea, I have the idle screw all the way out.

 

[Hijinx]

Worked on the setup a bit more today. Still have a very slight bog off idle, nothing bad, probably only noticable to me. I plan to call BG tomorrow to discuss. I'll let ya'll know what I find out.

 

[Hijinx]

Now she is bogging bad with the A/C on. I'm thinking I may be a tooth off on the dist.?

 

[barrier5]

A tooth of on the dist. isnt going to make a difference,timing gears yes,dist. no.As long as you can twist the dist. enough to time it without running the vac,advance unit into the manifold you should be alright.
I'm not up to spec on the Demon,but is it a Qjet replacement?If it is do you have the tin blockoff gasket on the intake ( goes between the manifold and the paper gasket ),if not you could be sucking air right there.

 

[page62]

Which engine? What's the cfm rating of the carb? What intake manifold? Do you have an A/C idle solenoid? Any other details you can toss in?

 

[Hijinx]

Running way to much cfm for the engine (750, should be 650). However, I bought it with a though to the future where I plan to drop in a 380 - 400 hp stroker in. I think I figured out part of my problem. I had to use a carb spacer and I used an open spacer. I think I am losing the signal due to this and defeating the dual plane intake I have in place. I plan to pick up an 4 hole spacer today along with a larger set of squirters for the carb. That should help out a lot. If not, I will start messing with the air bleeds. I have decided now that it has to do with having to much carb on a 200 HP motor. Demon has been a lot of help. They have a good tech group.

Like I said, I'll detail all this out for you guys in my next column. That is if I dont light myself on fire from the fuel fumes comming out of my clothes!:crazy

 

[BobbyBJr]

I'm not by any means a mechanic, but I had similiar problems with my 75. I adjusted and adjusted the carb and played with the timimg and was about ready to send the carb out to be rebuilt when the car just quit all together and would not fire at all. I replaced the points and condensor, ignition coil and plugs and the thing ran better than ever. The carb problems magically went away and haven't returned. The only reason I mention this is that I notice you have a 73 and I have been told that the engine and distributor and all on my 75 is from a 73. Just a thought.

Bobby

 

[Hijinx]

Thanks Bobby. I put in an Ignitor II ignition last year to fix all those issues. I do believe that I have some small nagging ignition issue, however;

Yesterday I picked up a 4 hole 1 inch spacer. I, now that I really take time and think it through, had boned up by getting an open spacer. :duh The signal from the carb was getting screwed up going into my dual plane intake with that big open space between it and the carb. That helped a lot.

Secondly, I got a larger primary squirter (#37), and that cleaned up my stumble/bog off idle.

With both of these things done throttle response is chrisp and I only have an almost unnoticable hesitation just off idle. Was able to lean it out as well.

Only remaining problem, which I just got off the phone with BG on, is that the car will die under hard braking. Seems that I have the float set too high. I'll change that today.