The springs only control the rpm of the start of the advance and the rate with which it advances.
They have absolutely nothing to do with the amount of advance, that function is solely controlled by the particular advance cam that is installed upon the distributor in question at the time.
Some 17 different advance cams were used for all Pontiac HEI applications and of that , 4 are of particularly good interest. The rest are rather so so. You have to watch these advance cams and worthy of note are the ones that allow an excessive amount or extra advance beyond what the springs will allow. By that I mean no matter what cam you use if the springs are so light(such as the hair thin copper colored ones in the mr gasket/moroso kit, excessive amounts of advance will be present as the center cam will be overcome by the springs that arent anywhere close to the correct tension and at that point the advance cam can no longer do its job as intended. We call this excessive override and it is in fact a very real issue using too light of springs.
There is a chart (2 actually), one that I compiled many years back and a second one that our very own Rocky Rotella compiled about some 6 mounths later that both show this info I am speaking of.
As far as it bears on this conversation since the Moroso/mr gasket kits were brought up, let me step out of cue here and address this one more time.
There is a factory GM weights and center cam are going to be the best ypu will lay your hands on ever, period. There is a steel is heat treated and they will ring like a crystal glass when dropped on the floor. As such they are very durable…
The aftermarket curve kits mentioned suffer two very serious issues right off the bat straight out of the package, and are why folks in the know avoid them like Ebola .
First they are of mild steel construction. Under operational conditions inside the cap they will rust and powder up far worse and much faster than the originals., which in case you were wondering is why the GM pieces are heat treated.
Second, unless they changed something the design of the weights are such that they could become hung up on the tips of each other upon deployment or retraction a slight amount if the weight hole and weight pin interface wasn’t ideal. Seen this happen multiple times.
A third unmentioned issue is the higher the rom you turn it the farther the advance keeps going. This is due solely to the design of the advance cam itself in these kits.
No telling how many have been sold over the years but I’ll tell you this I’ve filled 2 5 gallon Berryman carb cleaner buckets with them over the years correction the poor advance from these things.
I would avoid them if it were me and I will not use them here for these specific reasons.
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