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Timing marks with a new cam

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Old Dec 18, 2007 | 07:13 AM
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Default Timing marks with a new cam

Just put a new engine in and I used an after market cam that I bought from the machine shop. I dont know what the numbers are, but it has a pretty good bump to it. Works very well. Question is when I hooked up the timing light the mark seems to jump all over. Is that normal and if so how do I set the mark? Thanks Randy
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Old Dec 18, 2007 | 07:28 AM
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Is everything new?
Jumping timing is generally a sign of a worn distributor, it may need to be shimmed. Thats a detail a lot of shops miss. What kind of light do you have, the inductive clip needs to be on the #1 plug close to the plug and there should be an arrow on the clip indicating which way
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Old Dec 18, 2007 | 07:51 AM
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Yes all is new except for the distributor, I had bought it about three years ago. It is a Mallory HEI. Question is even with a bigger cam the lines should not jump should they?
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Old Dec 18, 2007 | 08:32 AM
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No, they should be pretty stable
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Old Dec 18, 2007 | 09:38 AM
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Possibly with the new lumpy cam it has a choppy/higher idle that is pulling the mechanical advance in and out....?
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Old Dec 18, 2007 | 10:58 AM
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Originally Posted by yellow 72
Possibly with the new lumpy cam it has a choppy/higher idle that is pulling the mechanical advance in and out....?
Good point.

81vettelover1, are you still on the idle circuit at idle? What's your RPMs at idle?
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Old Dec 18, 2007 | 05:34 PM
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My idle is about 800, the cam like I said is pretty choppy. Could I be pulling the advance even thou the vacuum line is off?
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Old Dec 25, 2007 | 11:29 PM
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Originally Posted by 81vettelover1
My idle is about 800, the cam like I said is pretty choppy. Could I be pulling the advance even thou the vacuum line is off?
Yes...like what Yellow 72 said. Check the springs and make sure that they're not too weak.
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Old Dec 26, 2007 | 01:03 PM
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What does the timing read at 3,000 RPMS and is it steady, you should be shooting for a steady 36 degrees at that point, no vacum.
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