this is on my 1972 dart with 9.4 to 1 440. It had the stock electronic ignition setup and I had the timing dialed in perfect. Been this way for years. Well, all I did was change the mopar ignition box and coil for the GM HEI coil and module for a hotter spark and that calls for opening the plug gap to .045. It all does well and starts easier and all but now it pings bad when hammering down the throttle wide open...should the hotter spark cause this and if so, now whar?

What is the total timing all in?

I was going to say to double-check that your timing didn't change. I don't think the hotter spark and wider gap will affect pinging.

Like said, double check the timing.

X4 something else was changed (which changed your curve). You might plot the curve then toss the old box/coil back in & plot its curve & compare em. reportedly orange (& maybe other) boxes can pull timing so if the HEI did not ( I believe it is good regarding that) then that could (inadvertently) have pushed you over the limit by default

well, i wasnt using the orange box, it was just a parts house cheapo, wondering if they also pulled timing like the orange box because that would explain it! I have not messed with the distributor at all so..

So. Get a timing light and see where the timing is. Why play a guessing game when you can verify something critical and basic easily.

I will do that, but i was wondering if anyone here knows if all the cheap parts house mopar boxes retarded the timing as well like the MP orange one did..?

No mystery to me. Your empirical data seems to show that your Mopar-like box was a little slow on the uptake. You'll have to redo your ignition advance.

"Pulls timing" usually refers to making the spark later and later as engine rpm goes up. In your case as it seems to be doing it right from idle, I'd call it a built-in delay.

R.

Did you reset your timing after you changed parts ?

This.
pertronix swap even has a warning on the instructions, that changing it may cause timing changes, even if you didn't do anything else.
the part that controls the spark is known to cause timing changes. not a surprise.

well damn, i sure didnt realize this. Sucks because years ago i went through a bunch of trial and error getting the advance right, i JB welded the advance slot and gradually filed it out until it was where it needed to be, so, now i guess i have to do all that over again..

I don't think so. You just need to reset your base timing to the old spec. That way you will have kept the spark occurrence at the same crankshaft position.

With the timing light, watch your timing mark and twist the distributor until the timing mark is where you put it before. This isn't exact at any other than idle, but it should be pretty close and may not have to be changed.

R.

Other thoughts: THANK YOU for the JB Weld suggestion, I am ashamed that, as the self-proclaimed Prince of Goop, I didn't think of it first!

And speaking of being first, I am contemplating suing Gwyneth Paltrow for illegal use of part of my name for her Website's name. I used it first. Oh darn, there's a polyurethane glue out there called Goop which was probably ahead of me.

R.

I would for sure before I did any changes, plot the 2 curves, if you dont have a dialback you can make marks on the dampener at say 17.5 20 22.5 25 27.5 30 32.5 35. Your timing tab will cover you to 15 then cut/measure a strip of paper with your calipers for a ruler & 0.0632683" is (1) degree & IE 35.5 degrees is 2&1/4" (2.246"). EDIT just note (1) the RPM you reach each point at (2) total degrees (& at what RPM) (3) compare the two. getting a baseline comes first

ok, i have timing tape on the balancer and everything marked. I originally had the initial at 17 degrees and the total was 32 degrees. Well, i checked it today with my light and the initial was still at 17 but the total would go up to around 42!! So, yes, i am going to have to pull the distributor and fill in the advance slot some more and then file it to where it needs to be.. so changing the ignition did not change the initial but it did change the total..I retarded the timing back to 14 initial and it helped the spark knocking when going WOT tremendously, but thats just not enough initial, doesnt even sound right..

that definitely explains what caused the pinging! but a box/coil ch would not account for a 10 deg increase in total.. Sumpin else changed: (slots). EDIT but the slots did not change, we're missing something/makes no sense

no sense at all..lol..sucks i have to tear down the dizzy and do this all over again..

when you get inside the dist as you know holler if you see anything that has changed

Will do Rob! I would just leave it with the initial down to 12-14 but it doesnt seem as strong off the line as it does with the initial up around 18..