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ignition timing questions
https://slantsix.org/forum/viewtopic.php?t=6663		 Page 1 of 1
Author:  225dart [ Fri Aug 22, 2003 2:45 pm ]
Post subject:  ignition timing questions
hey guys, went to the track again today and while checking the timing, i noticed it somehow got to 39 degreestotal (way too much), i know it was at 32 before so my guess with out looking is that the weights were stuck and now they arent. sooooo, i set it back to 34 degrees total and you know what happened next--it went faster. dropped a tenth in the extreme humidity we had today--it actually was spinning a bit on the greasy track surface(no traction compound applied on track rental days). i remember a few of you said 30-32 was about it for a basically stock setup--stock cam. but, what i want to know is how much initial can i run so i can modify the advance plate to accept the more initial and less mechanical. i thought i read that 12-15 initial was ok on a stock cam--true? and am i thinking right that 30-32 was the max total?. i have about 2 more times i can get back to the track this year so i want to make the best effort (in street trim)to get this pig down into the 18's before i throw the header and supersix intake on it. im running mid nineteens in the heat and low 19s in good weather. thanks for help

--chad
Author:  MitchB [ Fri Aug 22, 2003 6:59 pm ]
Post subject: 
The spark timing is soooo dependant on the particular setup in question that a universal, fits all answer really does not exist. Do you know how you figure this out on an 'unknown' combination? You look at two things: intake manifold vacuum and exhaust temperature right off the exhaust port. The idea is to increase initial timing until you get no further increase in manifold vacuum and no further decrease in EGT. What you are really looking at is combustion speed and this is a function of chamber design, valve timing, port velocity and a bunch of other variables. I can tell you this: I run 14 degrees of initial with an otherwise stock slant with about 9.5:1 compression, 28 degrees total all in by about 2400 RPM. I don't drag race my car.

Mitch
Author:  225dart [ Sat Aug 23, 2003 7:06 am ]
Post subject: 
yes, there are many variables to timing, that is true. these motors seem to break the "typical setep" of a v8 motor. my "mild :wink: " small block had 18 deg initial and 37 total. a slant does not seem to like this type of setup. i ave a stock 318 also that has 15 initial and 38 total, again, not the way a slant seems to like to run. im just mearly looking for a ball park to start in as im still gaining knowledge on these. by the way, i did not know that you could take egt's into the timing realm either. thats a great tip. i wish that the price of those kits to check stuff like that would come down though. i just use your basic vacum gauge and dialback light for my stuff. i will start at about 10-15 initial and play with that and then modify the andvance plate to get me the rest. thanks,

--chad
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