Stovebolt 5200 carb tuning

[barishiman]

I fiddled with the carb again this morning. Took a few laps around the neighborhood and decided to take down to the gas station. It drove great except for the tranni not shifting correctly. I think its coming down to tuning the carb correclty and timing. I hooked up the tach and show my idle speed was 1200! So I backed it down to 900 and it was still running smooth. This is with the choke wide open. I then took off the tach and closed the choke and thortled up the engine. The engine then jumped up in rpms and was stuck in a fast idle, like 1500+ rpms.

At 900 RPMs when I shift it from park to drive the engine dies. But when I had it at 1200 RPMs while shifting from park to drive, it kept idling in gear. What's the deal with that?!?!

Sometime tomorrow or tonight I plan to check the timing again and then fiddle with the carb some more. I know I"m getting close. I've been reading in my shop manual on carb adjustments getting a rough idea on tuning this 5200. What do you guys think?

 

[amartin83]

Idling at 900 rpm is too high as the progression holes in the carb begin to open and the car begins to run on the carbs main circuit. Make sure to adjust your idle to about 650-700 RPM and set the mixture screw for best running at that point. The actual setting for the idle screw (not mixture screw) should 1/2 turn past the point where it just contacts the throttle arm. Mixture screw should be about 1/2 to 2 turns out, any more or less means you need to rejet, but the carb should be jetted to work fine as it is. Make sure that when you are adjusting your idle mixture the choke is in the fully open position to prevent the fast idle cam from bumping up your idle and throwing you off. Of course make sure your timing is correctly set too. You could also have a vacuum leak (very likely) and make sure your kickdown cable is readjusted.

 

[barishiman]

I'll back tomorrow morning and look everything over. The last time I made an attempt to get my car to idle low was at 800 RPM in neutral before it would shift it into drive and then it would die in gear. I'll try again and see if I can drop the RPMs some more.

 

[barishiman]

I think I've found the sweet spot. I got the timing light out and tried to find my timing mark. Well, I did but its way out there. The mark is sitting below the thermostat housing. I had this problem last time. So I pretty much ruled out the timing light from there and hooked up my tach. I tweaked the carb and got the engine to idle as low as 900 RPM in Park. This feels extremely fast idle to me. Well, then I put the car in drive and the RPMs dropped around 600. It stayed running, but I tweaked alittle more on the carb and got it running smooth. For the most part the engine runs very smooth. All my vaccum looks good. I did a few laps in my neighborhood. The thortle was excellent, stayed idling, didn't die in corners. Then I thought I need to get this car on the road.

I took the car out for a drive for a road test. Mind it there was no hood, front grille, headlights, bumper, open exhaust, and the expired tag. Boy was just waiting to be pulled over. The car drove good and it felt great to drive the old mustang after a year. Laura (the mustang) was happy. I know she was grinning. When I put my foot in it, boy did I feel her jump. That 2 brl carb really does the trick. A few more test drives are coming up and I'm looking for an exhaust system. I still can't decide on glasspacks or turbo mufflers.