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This question is specific to the haltech elite similar to the webinar that was recently run on the subject using the same ecu.
The question is in reference to the TDC offset angle that you use to bring the ignition timing in sync. Does the absolute numeric value of this parameter have any relevance? I noticed you were up in the 680-690 range in your example, but I have a car brought to me with an elite and the value is currently at 462. I guess what I am asking is how do you know where to start? Does the elite have a number in there as default? How does this all work?
I understand the process apart from this, but I just wanted to be sure I am not missing anything, especially with the fact that sometimes you may need to add 360 degrees to this value. If that were required, would it be evident in any other way apart from the car not starting at all?
I'm not 100% sure what Haltech use for the TDC reference. This seems to vary from manufacturer to manufacturer and may be something like the number of crankshaft degrees between TDC #1 firing and the first sync tooth after a missing tooth or similar. In our respect it really doesn't matter. We just need to understand the process for correctly setting it. For popular engines with a fixed trigger pattern like the VQ35 Haltech should be able to advise on a solid starting point.
If your offset is 360 out then you'll still see the timing align correctly with the timing light but there will be no sign of the engine wanting to fire. You may possibly hear the engine essentially 'sneeze' out the exhaust.
In terms of the actual timing marks, on the 350 I notice that there is one fixed reference and then three marks on the pulley. On the car I am setting it's the total opposite. There are three reference marks on the engine block and then one mark on the pulley itself. See attached photo. Is their any difference in the way you go about setting the base ignition timing on both of these?
It really doesn't matter where the marks are - pulley or front cover, provided you know what the markings mean which in your case is very obvious. The actual process is identical. Choose a base timing value you can easily see without parallax error and then adjust your offset until the timing you see on the laptop matches what you're seeing with the timing light.
With the SBC, manufacturing tolerances may be a little less close than some more modern vehicles, especially with a mix of OEM and aftermarket - I would suggest you check the true TDC and either make your own mark, or adjust the timing plate to match. Adjustable tabs and pointers are available for that engine - just make sure you have the right type front cover and balancer diameter.
As an aside, where the fixed mark/pointer is on the engine, the marks on the pulley are TDC to the left and advance clockwise. Where there is a fixed mark on the pulley/balancer, the right end is TDC and advance is to the left. A trap for beginners that has caught a lot of apprentices out (avoids looking in mirror...).
For example - https://www.summitracing.com/int/search/brand/summit-racing/part-type/timing-pointers?SortBy=Default&SortOrder=Ascending&retaillocation=int which would work perfectly well with an aftermarket damper with timing marks already machined on it.