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A friend has a 1971 Country Squire wagon with a 390 and he's getting a miss. It had been sitting for 10+ years we're begining to suspect it may've been parked because of this miss. It's not a hard miss but it is noticeable at idle and in higher RPM. Everything's stock. All the basics have been done. Compression check is good, carbm was rebuilt (and rechecked 3 times), all ignition components have been replaced (cap, rotor, plugs, wires, condenser, coil, swapped out a distributor). Timing, and dwell has been set. Also replaced the fuel pump, it's running off a small gas tank from under the hood. Measured the cam lift at the rocker arms. We did a cylinder balance test and couldn't pin it down to any cylinder. And that's where it sits today, any more ideas?
 

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Thanks, I'll check the plug wires. The fuel is running from a mower gas tank under the hood. There's no fuel filter as this is a temporary setup. The real tank was pretty filthy so he had it professionally cleaned but hasn't reinstalled it yet. The gas isn't new, but it's less than a year old. Also it's a 70 not a 71 if that makes a difference.
 

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Put a vacuum (diagnostic) gauge on it. No better diagnostic tool.
 

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We did put a vacuum gauge to it and it was in the normal range, but the needle bounced around due to the miss.
 

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We did put a vacuum gauge to it and it was in the normal range,

but the needle bounced around due to the miss.
If the needle bounced around, it was not within the normal range. Do you have a diagnostic chart that came with the gauge?
 

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Is the miss consistent or random? A temp gun on the exhaust will isolate the cylinder. then you can swap componets to isolate the problem. New does not equal good.
 
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