Base timing. Really ?
Glad i stumbled onto this post before i made a new one. On my 440 with 284/484 cam installed 2 degrees advance, 9.4:1 compression, street dominator intake, 3000stall convertor in a 1972 dart, I have the electronic ignition with an FBO limiter plate in it and if i remember right, 1 spring in the distributor. Timing is at 20 initial and 34 total. The timing is all in by 2800. I THINK too light of a spring is the issue and after reading all this i really think it is the issue, but when laying into the throttle at lower RPM's, like under 3500 i guess, it detonates a little, but i dont hear it if i lay into it when the rpm is higher..Thoughts?
What the ignition is doesn't matter too much under 3000 rpm. They'll all get the kernal started within a degree of each other although the HEI
might provide slightly better growth if combustion conditions are less ideal. So dont worry about that change as far as its effect on the timing.
The limiter plate and the signle spring are what is making it difficult.
Whether limiting the advance will work or not depends on a number of variables.
20 initial , how about the vac advance ? do you use one ? That may be adding to your problem. I would also add 1 soft spring. Common set up seems to be 1 soft stock spring , ditch the thick stock spring, and install a soft aftermarket one ( mr gasket )
It is a common setup but its not a good setup for street/road uses and with electronic ignition its not the best for drag strip either. That's one of things that Yellow Rose and Bill Baldwin are showing in their videos.
(Add a spring will delay )
Yes. And where it will delay the advance will depend on the details
It depends on the tension force the spring applies to the weight. That in turn depends on the spring length, the spring perch positions and how far out the weight is, if at all.
This was with the mopar ECU. I also had it dialed back to 16 degrees BTDC. Since then i have done the GM HEI module conversion hiding it in the gutted mopar ECU and also installed one of the FBO plates and am in the process of getting it right. I find it like 20* initial better than the 16 but like i was saying, it detonates slightly when nailing it under 3500 rpm and figured the timing needed to be slowed down. I know it comes all in quickly with the spring i have in it. all in before 2200.
Liked 20* better in gear or out of gear?
Out of gear means little, and with an automatic transmission even less.
If you want to stick with the FBO plate, you may have trouble using vacuum advance. Limiting the advance can work, with the right springs in some engines.
If your not married to the FBO limiter and you have the original springs, then it may be easier and better to shorten the slots on the inside.
I've posted about this before. really don't have time right now to repost it. I'll see if I can find some links.
