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By JRcustomline - 15 Years Ago
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Help experts! I am new to fords! I have a 55 customline 272 with a fordOmatic and it won't idle properly in gear. I checked the cam lobe lift using a dial indicator and it is approximately .270 The rockers are stamped 6564 which I understand are 1.54:1 which should result in about 415valve lift (sounds reasonable). It has an edlebrock 4303 500cfm carb on stock manifold, I checked the compression 130psi, I replaced the stock dist with an MSD distributor (mech and vac advance) set to 6deg BTDC at idle and 32deg advance all in at about 4000rpm, new wires and sparkplugs. If I set the idle at 500 rpm than it stalls when put in gear, so I set the idle at approx 800 rpm and in gear it idles at about 600 rpm but shakes the car pretty bad. Complicating the matter is aftermarket air conditioning which loads the engine at idle by about 100 rpm. I had the intake smoked for vacuum leaks and non found, and the idle vacuum is about 15in. I am thinking now maybe there is something wrong with the transmission. If you just leave it in neutral and turn on the A/C it still idles ok, but when put in gear it gets a bad case of the shakes. Any advice would be greatly appreciated. Oh one other thing it has been converted to power front disk brakes. The power booster does not appear to be leaking.
John R
Austin, Texas
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By GREENBIRD56 - 15 Years Ago
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Glad to know you John - try adjusting the initial advance up to 10° - the extra 4° will result in 36° total (with no vacuum connected to the advance pot). The idle manifold vacuum should rise a bit - and so should the idle speed. Tweak your idle mixture screws for max speed - reset your throttle stop - and then tweak them again if necessary. The 36° won't hurt your engine - and you might see if you've got a spring set that will get the total in closer to 3000 rpm. The manifold is divided into a "cross H" pattern - so that the two sides of the carb are feeding alternate cylinders in the firing order. Take a look to see if the plugs fed by one side or the other are rich or lean. You might have an odd float level side to side.
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By oldcarmark - 15 Years Ago
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Hi Steve! If the idle speed is being raised to 800 to prevent stalling and it runs rough in gear is it possible the throttle plate is open too far and too much of the transfer slot is exposed?Is this carb similar to the Holley where only a slight amount of the transfer slot is exposed to vacuum?It sounds like a silmilar situation I had with mine when I would have sworn there was a problem with the Fordomatic.Turned out part of the problem was the throttle plate was open too far.With late model cars there is a solenoid that activates to increase engine idle speed when A/C is engaged.Sounds like he may have to play with the secondary throttle plate to get enough air with the primary set at maximum open as far as the transfer slot.OR drill small holes in the primary throttle plate.Just some ideas.I agree with your suggestions on timing.All advance in by 2800-3000 RPM not 4000.Advancing initial timing would allow the idle speed to be turned down a little.
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By JRcustomline - 15 Years Ago
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Thanks for the advice. I can adjust the dist advance curve with springs and bushings to give proper timing starting at 10deg idle and all in at 3000 if that would help. The shop manual however calls for 6 deg at idle and all in at 4000, that is why I set it up that way. Also I agree I should add a solenoid to kick up the idle when A/C is turned on. However in the Texas summer the A/C is always on.
John
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By oldcarmark - 15 Years Ago
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The manual does call for 6 BTDC however y-blocks like a little more advance.Try 10.I think your idle problem is carb adjustment related.Wait until Steve(Greenbird56) comes back with some more input on that subject.I had the same experience with mine and really thought I had a transmission problem.Everybodies first reaction to set idle speed is to crank the screw until speed increases to a satisfactory speed.On the Holley there is a recomended maximum opening for the primary throttle plates.Once you go past that setting you start drawing fuel from the transition slots which really messes up your idle settings.I dont know for sure but I would assume the Edelbrock has similar adjustment settings.As I mentioned Steve is more knowledgeable about that than I am.
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By YellowWing - 15 Years Ago
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John, I think adding timing would be a good start. My moderately modified would not behave until I set initial timing to 16 degrees. Mike
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By oldcarmark - 15 Years Ago
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Hi Mike! Are you using ported or non ported vacuum to control your vacuum advance?
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By YellowWing - 15 Years Ago
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I'm using ported vacuum.
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By Hoosier Hurricane - 15 Years Ago
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The manuals for FOM cars is to set the idle speed IN GEAR, so 500 in gear is about right. Leaky or improperly adjusted valves can also cause rough idle. So can a stretched timing chain.
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