I've been advancing the base timing on my 1980 Aspen. I've advanced, in stages, the timing from 10 BTC to 14 and now 18 degrees. I also have the vacuum advance diaphragm adjusting screw backed out for quickest advance. So far, there's been no detonation. Can anyone tell me what the total timing is in my distributor and about what total timing I should run? The car has the 1 bbl /6.

Thanks

Mitch

mb589@aol.com

SL6 distributors were set-up with all sorts of "totals". There is sometimes a tag under one of the screws which has the mechanical advance amount on it. Early distributors had this number stamped into the housing.

Best bet is to check yours with a timing light. you can use the "tab and put some additional marks on the pulley, my tab goes from 0 (zero) to 15º, so I mark the pulley at 15º, move that mark to 0, mark at 15º again, (that's your 30º point)move that to 0, now mark every 5º, (35º, 40º, 45º)
I just "pencil mark" at 15º but punch-in and paint 30, 35, 40, 45º.

Now you can watch with a timing light and rev her up to see what you get. Total for a SL6 *without* vacuum advance hooked-up should be 30 -35º and 48-52º with vacuum advance added.
DD
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: Mitch

<FONT COLOR="0000ff">At what RPM is this 30 -35º ?? All mine have ever been able to tolerate is 20 -22º at 2500 or so RPM under load with out lots of pinging. Yes, my timing marks I believe are accurate. I have a advance timing light and it also seems to be accurate everywhich way I check it. And this is true on different engine in both my car and truck.</FONT>


cfield@ll.net

Advance curves need to be "dialed-in" for each set-up. The 30 to 35 degrees quoted is what I'm currently using on my dragcar and I will most likly need to adjust it the weekend seeing the engine combo has changed.

Timing is related to cylinder presure at TDC compression. What is your "cranking compression?
Compression ratio, ring seal, cam, intake track, exhaust system, headwork all have an effect on this. There is no "one size fits all" SL6 advance curve, you need to find the initial setting the engine likes (8-10 degrees) then set the mechanical. (another 16-22 degrees plus the spring "rates")
The vacuum advance pod should be the final thing you "tweek-in", usually with lots of trial & error driving time.

The age old rule applies, bring in lot's of advance as fast as possible without "pings". Run the combos on a stop watch or dragstrip clock to fine-tune, then tell us all about where you ended-up.
DD