What are the downfalls of running too fast of an advance curve? How can I tell if the curve is too fast? I'm assuming if it's too slow it'll be noticeable seat-of-pants wise?

Reason I ask, is I put the yellow and blue springs (lightest and second lightest) from bigslant6fan's spring kit in my Dart (mild slant, stock stall, 2.76 gear w/24" tire) and I'm under the impression that it's too fast. I idle around 600, and advance don't start till 900 according to his graph... I'm also under the impression that you want a 2 stage advance, not two springs of the same rate? Would blue and green be better? I've got super six and '76 springs too.

So is this too fast? Should I want advance to be higher than my choke idle? Please bare with me, it's just taking me a while to wrap my brain around some of this I guess

Cons of too much timing advance:
Cylinder pressure peaks too soon doing negative work on the piston. Seen mostly as a power loss.
Pinging/detonation. If excessive can cause engine damage and loss of fuel economy.
Emissions. Advanced timing leads to higher combustion temperatures and an increase in NOX emissions.

A 2-stage advance can help top end power as more timing advance can be tolerated and useful above the peak torque RPM.

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Joshua

I plan an advance curve this way:

I figure the amount of total advance I want at peak torque (example sbc 34degrees)

I figure what static advance I need to start the thing (sbc 10:1cr 8 degrees)

that means my advance curve starts just off idle and increases by a total of 34 minus 8 = 26 degrees of mechanical advance.

Plug in vac advance to get more advance at an idle and cruise.

The transition from idle.... static + vacuum ......to static + vacuum + mechanical is where stumbles and bog begin and end.

The stomp of the pedal causes the vacuum part of the advance to disappear ,,,,so you need a good part of your mechanical advance to be added right away....then level off to your peak torque RPM ( 2000 - 2200 rpm)

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Yeah....Im the one who destroyed this rare, vintage automobile.....

I just put the Blue (for the lightest) and Black springs in my distributor.

Definite pinging there at WOT. Even at half. I have a short slot distributor and the 8.5 can on it, but I haven't had the slot welded to .38 yet. That's my next plan.

It tried the green/black combo, too, and the blue is far peppier.

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

I use the blue and green combo, seems to work well, no pinging, it goes all in by 2600rpm or thereabouts.

brian

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https://tinyurl.com/yynpj4v2

Yep, I swapped the yellow for a green, and bumped the initial from 6*BTDC to 8, and it seemed to like it. Ran better than it ever had.




Then I melted a hole the #3.

Not sure that was the cause tho. Teardown and investigation happening shortly, another thread with some more questions on the way.