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1979 F150 Ranger
400 Windsor engine with 2bbr mastercraft 2150
New fuel pump, filter, plugs, wires, odds and ends.
Battery is good, spark tested to all wires and coil is pulling 7volts positive to ground. Double checked plugs and they look nicely tan with nothing odd. I also pulled the valve covers to check for stuck valves and it’s super clean in there. Currently burning through heet and
A engine cleaner additive to gas.I have been working on this truck and replacing several parts to fix he idle issues. I just replaced the carb with a rebuilt stock mastercraft 2150. The timing and mixture has me a bit stumped.
Stock timing is 6* btdc. It seems to run rough at that timing so I used a vacuum gauge to get is to a steady 22in vacuum. Problem is now it does 2 things.
1. Occasionally backfires through the carb when reving
2. Stalls out when hitting gas from a stop or slow pace, such as going around corners or stop lights, etc.Thoughts?
Thanks
C
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It sounds to me like your rebuilt carb hasn’t been set up. Adjusting the timing to compensate only masks the problem and can cause your misfiring. You need to check the setup on your carb. Float height, air/fuel mixture, proper jet sizes, etc. There’s more to a carb than just curb idle, and all carbs have to be adjusted post-install. They rarely work properly just ‘out of the box’ and bolted on.
What condition is the distributor in?
You did not say what the timing is at that 22″ of vacuum, so it may be too far advanced for the “initial” timing?
I would check the advance curve, it may be stuck, or could have a broken spring?
Checking advance curve is done with vacuum advance disconnected. I would also check the PCV valve, and carb float level.[quote=”coryj5″ post=186569]The timing and mixture has me a bit stumped.
Stock timing is 6* btdc. It seems to run rough at that timing so I used a vacuum gauge to get is to a steady 22in vacuum. Problem is now it does 2 things.
1. Occasionally backfires through the carb when reving
2. Stalls out when hitting gas from a stop or slow pace, such as going around corners or stop lights, etc.[/quote]Do you mean you altered the ignition timing (by rotating the distributor) to achieve the 22 inches of vacuum at idle?
The first thing I would do is to return the ignition timing to the proper setting, and then adjust the idle mixture screws (and the curb idle speed screw, as necessary) to get the best and steadiest vacuum gauge reading and idle quality. See what you get and take things from there. (Remember, when setting ignition timing, to remove the vacuum line to the vacuum advance diaphragm at the distributor, and to plug the vacuum line. A golf tee makes a great plug.)
How new are the timing chain and gears?
I’ll double check the timing. If I remember right it was about 10 or 12. The carb tuning makes good sense too. The oriellys guy said that too. The distributor is original and stock from 79, along with the timing chain.
Thanks for the advice! I adjusted the timing to factory six before top dead center. And I returned the carb mixture screws. It definitely runs better, Idles better, and stopped backfiring. I still however have the stalling issue. It got better with these adjustments but when I’m stopped I need to punch it to get through traffic it dies or stalls way down.
I looked at the float and the float seems to be sitting lower than level when I seat it. If this issue is caused by a rich condition would I not want to raise up the tab forcing the float lower into the bowl and less gas into the chamber in the carb?
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