I got a question for you guys, because ignition stuff has always been strange to me.

I got a junkard HEI (vac. advance) awhile back, and have been building it up a little for use on my 350 when I get a good carb for it.

Its got a Mallory coil, new cap and rotor, new wires, and just tonight, an advance curve kit.

I got the advance curve kit (Mr. Gasket one) because I know the curve was really lame on late '70s cars like what the dissy came out of. I got it all in the distributor now, but it came with three sets of springs, gold (stiff) sliver (med) black (light) and I'm not really sure which I should be using for best street performance. The sheet came with a graph showing the curves of the 3 springs, and the gold seemed to not advance much, and it didn't advance very quickly (about 12* max advance at 4500). The silver had a curve like the gold, but it advances a little more (about 17* max at 4000). Now the black springs have quite a bit more total advance and alot sooner (about 23* max at 3000)

The black spring seems alot wilder than the other two, but is that a good thing on a street motor? Which spring should I use?

The motor is a basically stock '79 Z28 motor (350) with a 5 speed and 3.73 behind it. It will have a regular, non-CC Qjet soon as well.

 

What cam are you using?

I am sort of confused by your wording. You say that those springs are the total timing. Are you sure you don't mean thats the timing that they add to the initial static timing to get total timing? i.e. static timing + (spring "rate") = total timing.

Well, if my assumption is correct about your wording, I would say run the spring combo that gives the total of maybe 30 or so @ 3000 rpm. But that's just me talking from my limited perception on ingitions.

 

Well, initial timing + what the springs add to it, yes. The engine just has the stock '79 Z28 cam, which is pretty tame.

So should I use the black springs? Thats what you are saying?

 

I've tried a number of spring kits from different manufacturers, and the little charts they give you are pretty well useless. The curve you get depends on the weights you have. Trial and error is probably best.

 

I was hoping it wouldn't come down to that, but I'm not surprised that it does.

Anyway, the weights are the ones that came with the set... the kit came with those 3 sets of springs, a set of weights, and a center plate.

 

I've used a couple of those, you have to keep an eye on the weights over time. They're some kind of a soft stamped pot metal ("chinesium" as some moderators would say), and I've had them get pretty beaten up from snapping closed all the time.

 

How well do the stock weights work with aftermarket springs? I kept the factory weights, just for this reason.

 

It's been a few years since I bought one, but I always hated the weights that came with the Mr Gasket HEI advance kit. I just used the springs with stock weights.

But, "stock weights" can vary a lot. The ones I'm talking about are the ones that come in the GMPP HEI distributor.

It really isn't "trial and error" so much as it is tuning. Mix and match to tune it where you want it. In the "old days", they called it "curving" the distributor on a distributor machine, although on the engine with timing tape or a marked damper works just fine (although you have to remove the cap for each change, unlike the distributor machine).

 

Are the factory HEI weights all the same, or are they different between cars (not including 'stock weight' variances)?

 

They vary between applications.