Timing

[gtxdude]

Have 318 about 250hp, trying to get timing right. Running Pertronix 11 with Accel super coil. Where do I want to be 34 -36 total advance at about 3000rpm? Is that to much? I do have the Classic HEI system but haven't had chance to get in yet. That has a lighter advance spring in already. Any idea where that total timing should be on the HEI and at what rpm? thanks

 

[Rapid Robert]

I would (1) set the initial with the "vac gauge method" which is max vac minus 1 in hg & that is your initial timing then (2) shorten the slots to get 35 total (& that is initial+slots with vac adv capped) then mix/match springs so you are just under the pinging point at WOT up thru the gears on your hottest/driest day no matter what RPM your combo maxes out at then (4) plugin/adj the can & want to stay just under the pinging point in everyday driving under varying load/rpm levels on your hottest/driest day. (CCW slows the onset of the curve/total from the can stays the same). bottom line you want to stay close to the pinging point but NEVER over it. Any pinging you can hear is way too much.

 

[Marcohotrod]

u are in the ballpark at 35 degrees around 3000, more important is a good amount of initial, around 15-17

 

[RustyRatRod]

If it is stock compression, you will want initial around 20* with the mechanical somewhere around 14-15* for a total of about 34-35. All in by 2500 will probably suffice, but it is something you will have to experiment with.

 

[gtxdude]

Set timing last night 3400 at 2500rpm,ran great at idling in garage. Hooked vacuum back up took out for spin, started popping at about 2000rpm. Back in garage scratching my head, didn't make sense. Wife was holding idle at 2500 no problem, then I realized only thing different was vacuum was unhooked when timing. Today I unhooked vacuum started it up and took it up past 3500rpm no problem. Hooked vacuum back up to carb tried again, it started popping at about 2000rpm. So is it a bad vacuum advance module? would this cause the problem if not working correct?

 

[mod5v]

I have not been able to "use" the vacuum advance as designed on any non stock motors. I personally set my total advance on a sbm at 34* max and around 20 initial. I have pluged in a scanner on several "modern" engines and monitored the spark advance. I have yet to see one exceed 34*. I believe the "vacuum" advance was more of a emissions/bandaid for factory stock old lady driving that any millage/performance useage. THIS IS JUST MY OPINION/EXPERIANCE.

and I suck at spelling too.

 

[Johnny Mac]

I have not been able to "use" the vacuum advance as designed on any non stock motors. I personally set my total advance on a sbm at 34* max and around 20 initial. I have pluged in a scanner on several "modern" engines and monitored the spark advance. I have yet to see one exceed 34*. I believe the "vacuum" advance was more of a emissions/bandaid for factory stock old lady driving that any millage/performance useage. THIS IS JUST MY OPINION/EXPERIANCE.

and I suck at spelling too.

i have to agree, i'm sure there are some people smarter than me in here that can make a vac advance run perfectly, but i have tried on multiple GM and Mopar performance engines, and i always end up plugging it and forgetting it, because it causes more issues than it's worth for my purposes.