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Old 08-17-2010, 10:23 PM   #1
cj
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Default 5.7 LX timing issue?

Should the timing advance when set in base timing mode? Base timing is @ 10btc and about 12btc when purple/white wire is not grounded. Timing advances when revved whether or not it is in base timing mode.... is this normal. The engine starts pinging when i run over 4grand after a minute or so.......wondering if the module is shot and advancing the timing to much, if that is possible????? any ideas??
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Old 08-17-2010, 10:42 PM   #2
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when timing the engine..it should be in base mode....however if your getting ping at 4k rpm..you got other issues....maybe bad gas....only way to check timing advance I know of is with a timing light with the engine bay open so you can see how far it's advancing...but ping at 4k rpm may mean the timing isn't going far enough....

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Old 08-17-2010, 11:10 PM   #3
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I have timed it, and it is correct @ 10tdc in base mode, (12btc ungrounded) but it is hard to tell how far advanced it goes when i rev it cause the marks only go to 12btc, but i'm guessing somewhere between 20-30btc by the looks of it, which would be correct. I think I read that it should be somewhere around 25btc by 1700rpm and max 32btc???? but it advances in base mode and normal mode. I understood that it shouldn't advance if your in base timing mode? It also seemed to have a miss, so I checked the plugs and 2 where finger tight, so that may have been the problem. It runs great in the driveway, just need to water test it.....cheers
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Old 08-18-2010, 02:10 PM   #4
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CJ,

You are likely seeing the timing advance because of the mechanical advance system. If you pull the cap and rotor off the distributor you'll see the springs and weights that make up the mechanical advance. Since it's mechanical it couldn't care less what wires are grounded - it's going to advance regardless.

Off the top of my head 25* by 1700 seems like a lot on a small block, and I'd be surprised if it tops out at 32* - but I don't have any idea that the advance curve looks like on that engine.

Like SP said you'll need a timing light. Buy or rent a "dial back" light - Sears has them. They allow you to easily tell what your total is and, with a clip on tach, where it is. A cheaper route is to put a timing tape around the balancer if you can get to it.

If it's pinging at 4K you've got either too much timing, too much heat, or not enough octane.

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