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Anonymous
Guest
My 200 equipped Fairlane misses/surges at 1/4-1/2 throttle. H-w 5200 carb, new duraspark ignition. New carb from stovebolt. Could it need larger jets?????? Thanks in advance, Rob :roll:
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Anonymous
Guest
Hi Rob,
I'm not sure I fully understnd what you mean by misses / surges at 1/4 to 1/2 throttle. However, too lean a mixture could cause what I would call surges. Leaner yet, a miss.
If you drive the car on a flat surface at a steady throttle setting does the rpm tend to wander, is that a surge? If so, you are lean. If 5200 is a progressive carb. At 1/2 throttle you are running on the primary only. How does it run at full throttle. Smooth? Ping? Since the 5200 was used on a number of vehicles (Ford,Chevy,Chrysler), and mostly small 4's, it is not unusual to need to rejet when you put one on a 200.
Jets are in the bottom of the float bowl. Pull the top cover. Be careful not to damage the float, which is attached to the cover. Jet size is marked on the jet. Probably have to remove to read. Call Tom at Stovebolt. He will be more than happy to make a recommendation and send you jets at a very reasonable price. You may want to go up one size at a time until you get what you want. Shouldn't need to go up more than two sizes. Trial and error method but easy to do.
How about idle? This is a separate circuit with its own jets. Are you happy with the idle. Is the idle mixture screw sensative? These jets are on the outside of the carb. One on each side just above the mounting flange. The secondary idle jet serves only to keep the secondary circuit wet so that there is no hesitation / stumble / bog when the secondary opens. So the primary idle jet is the one to change, if change is needed.
Hope that helps. Don't hesitate to call Tom, very nice / helpful guy.
Steve
I'm not sure I fully understnd what you mean by misses / surges at 1/4 to 1/2 throttle. However, too lean a mixture could cause what I would call surges. Leaner yet, a miss.
If you drive the car on a flat surface at a steady throttle setting does the rpm tend to wander, is that a surge? If so, you are lean. If 5200 is a progressive carb. At 1/2 throttle you are running on the primary only. How does it run at full throttle. Smooth? Ping? Since the 5200 was used on a number of vehicles (Ford,Chevy,Chrysler), and mostly small 4's, it is not unusual to need to rejet when you put one on a 200.
Jets are in the bottom of the float bowl. Pull the top cover. Be careful not to damage the float, which is attached to the cover. Jet size is marked on the jet. Probably have to remove to read. Call Tom at Stovebolt. He will be more than happy to make a recommendation and send you jets at a very reasonable price. You may want to go up one size at a time until you get what you want. Shouldn't need to go up more than two sizes. Trial and error method but easy to do.
How about idle? This is a separate circuit with its own jets. Are you happy with the idle. Is the idle mixture screw sensative? These jets are on the outside of the carb. One on each side just above the mounting flange. The secondary idle jet serves only to keep the secondary circuit wet so that there is no hesitation / stumble / bog when the secondary opens. So the primary idle jet is the one to change, if change is needed.
Hope that helps. Don't hesitate to call Tom, very nice / helpful guy.
Steve
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Anonymous
Guest
Have you pulled the plugs yet? Many symptons can be caused by both lean and rich conditions. The plugs will tell you the story. I would first pull the plugs and see what they look like. Another trick to try is take the air cleaner off. Taking the air cleaner off will lean out your mixture. If the problem gets worse then it's to lean. If the problem gets better then you are to rich. If you don't feel comfortable taking a test drive without the filter and can of course do the opposite and tap up half of the filter to richen your mixture. If the problem gets worse your to rich.
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Anonymous
Guest
I recall that surging at idle could be timing related as well. Perhaps your vacuum advance is hooked up to full manifold vacuum instead of ported - I had that problem. Or you have a leak in your vac advance canister causing the timing to move around.
Just another thought.
Just another thought.
66200i6
Famous Member
I'll have to agree with Steve. I did quite a bit of testing with the Autolite 2100 on the FE390. By leaning out the main circuit, a definite "Surging" would develop during a 1/4 - 1/3 throttle. This would happen while maintaining a constant speed, on a flat road.
Bump up the main jet one step at a time until it stops and then watch those plugs. I ended up increased the jet size two steps after the “Surging†stopped.
Good luck, Ric.
Bump up the main jet one step at a time until it stops and then watch those plugs. I ended up increased the jet size two steps after the “Surging†stopped.
Good luck, Ric.
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