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Old 03-28-2008, 07:23 PM   #1
spikebot 81
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help... rough idle

I've been toubleshooting this shakey engine for 2 weeks now and cant seem to make any progress. I have noticed some black residue on the inside of distr. cap right in the center. Brand new acell dizzy. Ive installed new edle carb and intake, new wires and plugs. Check for vac leaks, none found. I have no smog stuff or ecm on the car. Adjusted valve lash. Timing at 12btdc 34 deg at 2500rpm . Engine has great power at WOT.Anyone got an idea?
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Old 03-28-2008, 07:44 PM   #2
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Sounds to me like there isn't proper ventilation of the gases in the distributor housing which in turn is causing gases to collect in the distributor cap and housing and, in the presence of high voltage and high heat is forming corrosive conductive deposits which results in internal arcing and misfiring. Check for clogged vent screens in the distributor housing.
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Old 03-28-2008, 07:53 PM   #3
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Ponch, Vent screens?
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Old 03-28-2008, 07:57 PM   #4
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Quote:
Originally Posted by spikebot 81 View Post
Ponch, Vent screens?
They're at the base of the distributor housing, about the diameter of a pencil eraser. You'll have to take the distributor out because they are difficult if not impossible to see while it's mounted.
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Old 03-28-2008, 08:03 PM   #5
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Ok, This distr doesnt have 50 miles on it. You think the holes could really be blocked?
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Old 03-28-2008, 08:06 PM   #6
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Ok, This distr doesnt have 50 miles on it. You think the holes could really be blocked?
Anything is possible, but it's a place to start. The symptoms you described are the same symptoms that are caused by blocked vent screens.
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Old 03-28-2008, 08:10 PM   #7
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I justed looked with a small mirror and dont see any holes at the base. This is a hei dizzy with vac advance. Sock dizzy and ecm is gone
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Old 03-28-2008, 08:25 PM   #8
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An old trick I still use is to pull 1 wire at a time off of the distributor cap until you find 1 that doesn't change the idle characteristics. Use plastic pliers (designed for this purpose) or a well-insulated tool. Pinch off vacuum lines to the carb. or intake to rule out an external vacuum leak.
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Old 03-28-2008, 08:34 PM   #9
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Big G, Ive tried all the easy stuff. No vac leaks on any hoses even tried starting fluid and the mapp gas trick around the intake and carb base. The car really runs strong when ya mash the pedal. I do notice that as the engine idles and shacks a bit the tach also jumps slightly. Make me beleive its ignition.
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Old 03-28-2008, 08:47 PM   #10
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This dizzy might be lemmon. When I was changing spings for mech advance I found all the screws loose to the vac assembly hold down. Fixed that. Then one of the lock tabs broke to the 4 pin connector on the cap. And now this black looking carbon around the center post inside the cap WTF. Anybody else with ideas before I yank this distr and send it back to summit?
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Old 03-28-2008, 10:22 PM   #11
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Quote:
Originally Posted by spikebot 81 View Post
I've been toubleshooting this shakey engine for 2 weeks now and cant seem to make any progress. I have noticed some black residue on the inside of distr. cap right in the center. Brand new acell dizzy. Ive installed new edle carb and intake, new wires and plugs. Check for vac leaks, none found. I have no smog stuff or ecm on the car. Adjusted valve lash. Timing at 12btdc 34 deg at 2500rpm . Engine has great power at WOT.Anyone got an idea?
Lets see if I have some of the cure,, Just went over my Hei "Accel with the help of B2B and TimAT,, # 1,, install a VC-1838 vac advance,, get that adjustable vac can off the dizzy, Get the weight springs Part number from Big2Bird and replace present springs with the Gold springs in the new kit, Then re time.. My pick control module " the black module in the dizzy" only lasted two weeks.. Replace that module with one from AZone. When changing the module,, evenly spread the heat sink white grease on the module back, that way you won't have hot spots.. These things I have done ,, did make a major change in how the engine idled and preforms... so that is how I solved several areas of problem.... good luck!
Also mew 8mm wires,, new AC-2 rapid fire plugs. I'm happy now
Rich
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Old 03-28-2008, 10:39 PM   #12
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Lets see if I have some of the cure,, Just went over my Hei "Accel with the help of B2B and TimAT,, # 1,, install a VC-1838 vac advance,, get that adjustable vac can off the dizzy, Get the weight springs Part number from Big2Bird and replace present springs with the Gold springs in the new kit, Then re time.. My pick control module " the black module in the dizzy" only lasted two weeks.. Replace that module with one from AZone. When changing the module,, evenly spread the heat sink white grease on the module back, that way you won't have hot spots.. These things I have done ,, did make a major change in how the engine idled and preforms... so that is how I solved several areas of problem.... good luck!
Also mew 8mm wires,, new AC-2 rapid fire plugs. I'm happy now
Rich
One more thing about your new dizzy,, They come with a dry shaft,, you have to mark the gear and the housing ,,, then knock out the drift pin,, then pull out the shaft, use heavy wheel packing grease, apply the grease to the shaft top rotating surface, re assemble the shaft back into the housing, mount gear to marks and replace drift pin.. doing this will stop heat and water vapor from coming into the dizzy from the block... maybe some one else can also jump in too.. in all lube that shaft,, have fun

Rich
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Old 03-29-2008, 05:45 AM   #13
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Anything is possible, but it's a place to start. The symptoms you described are the same symptoms that are caused by blocked vent screens.
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Old 03-29-2008, 05:59 AM   #14
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Old 03-29-2008, 06:35 AM   #15
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Redcherry or Big2bird, Is there a alternate vac can number other than 1838 in case napa does not stock this one
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