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On 11 Sep 2004 at 16:26, David Martinez wrote: > I want to be clear on some simple timing procedures involving, Dwell, RPM, > Advance. I started tweaking my timing this weekend due to heavy pinging > during load on my 67 Fasty. It started and idled fine, I had set the timing > @ 7 1/2 BTDC with the engine warm and the vaccum hose disconnected but once > it warmed up I experienced heavy pinging so today at a local swapmeet I got > a dwell meter. I had set the dwell to specification with a feeler gauge but > once I checked it with the meter I got today I noticed that according to the > TM I was setting it at about 33. The TM specified 42-54 so I forgot about > the feeler gauge method and decided to go with the reading on the meter as > the engine was running. Dwell is important to getting proper spark. If your cylinders are firing okay, then your dwell is acceptable. For most driving there is a wide range of acceptable dwell. Timing is different; it's important that you get it set just right. I'm not familiar with your tune-up specs, so I'm assuming that you're using the right timing settings. The advance mechanism(s) are important because they determine how your timing changes with RPM and load. It's important that you verify that your advance mechanism(s) are working correctly because otherwise your timing may only be correct at idle. I believe that your distributor only has a vacuum advance, so just suck on the hose and watch to verify that the breaker plate moves and stays put while you close off the end of the hose with the tip of your tongue. I keep a clean piece of windshield washer hose just for this purpose. Knock is a low-RPM, full throttle phenomenon. If your engine knocks, then you need to either increase the octane of your gas or decrease the compression. While it is possible to create knock in an otherwise good engine by mis-setting the timing or advance, it has to be WAY off to do this. When you use the dwell meter, note that there should be different scales for 4, 6, & 8 cyl engines. If yours does not have a 4 cylinder scale, just use the 8 cyl one and set your engine to a reading of 22-25 deg, which corresponds to 44- 50 deg for a 4 cyl engine. -- ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ Shameless link for search engines: http://listarchive.type3.org ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~