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Old 09-22-2012, 03:12pm   #1
69camfrk
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Default Point settings, spark knock and loss of power.

Helped a buddy change out rotor cap, points/condensor on his '70. The book called for .018 points gap and 8 degrees BTDC. We got rid of the spark knock after the points change, but timing was a little out. Spark knock went away, but the motor seemed to fall flat with full out throttle. Ok, rechecked points, reset timing, and spark knock came back as well as less performance. The motor is an original 350/330 horse motor, I think a L48. Looking for some ideas that I might be missing. Any advice would be appreciated. Thanks!!!
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Old 09-22-2012, 03:39pm   #2
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Check plug and coil wires. Even though functioning and throwing sparks, if not a full contact, could only be getting partial spark, especially the coil wire. Distributor cap could be bad as well, moisture, cracks?? Carb, fuel problems?
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Old 09-22-2012, 03:45pm   #3
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Use a vacuum gauge and dwell meter when you time it. I found that using a timing light on these older original engines can give a false reading. The vibration damper has usually slipped at least a few degrees, so the timing marks are off.

Set timing so it will have the most vacuum available from idle on, without any pinging on acceleration. If pinging, back the timing off just a bit.

Here's a quick read:

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Connect a vacuum gauge to a manifold vacuum source. Most engines will have a port at the base of the carburetor or throttle body where a gauge can be connected. Start the engine and observe the vacuum gauge reading.

Turn the distributor until the maximum vacuum gauge reading is noted. Back off one inch of vacuum from the maximum reading. Tighten the distributor hold down bolt. Normal readings average from 14 to 21 inches of vacuum depending on the condition of the engine.
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Old 09-22-2012, 05:06pm   #4
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What shape are the ignition wires? Try spraying water on them when its dark and see if you get a light show.
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Old 06-16-2014, 07:38pm   #5
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What octaine fuel are you using if the engine is a 350/350 and you are using regular gas it will ping. wouldn't burn anything else than at least 93 in it. the 70's were designed to burn high test. I won't burn anything but 93 in my 69 350/300. 10.25/1 compression ratio.
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Old 06-16-2014, 07:47pm   #6
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Pssssst,this thread is almost two years old.

Good info though that you posted.
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