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Discussion Starter #1
I have been playing around with the diffent advance springs that came with my MSD dizzy, and I have a question about how they relate to the initial timing. Based on 'seat of the pants' performance, I like the two lightest springs in there, which brings in the full timing by 2500 rpm or so. The guy at the dyno did not like running the light springs, because he said it caused the initial timing to be bumped way up after the car was taken into higher rpms. If the car is just warmed up, and idling with the light springs in, I have set the timing at 10 degrees initial previously, and it was working just fine. After spinning the car into higher rpms, and then letting it drop back down to idle, the timing then reads somewhere in the neighborhood of 20 degrees. Eventually, it will drop back down to the set 10 degrees, it just takes awhile due to the light springs. The guy at the dyno said this is a problem, but I don't see why. To me, this is not changing the initial timing, nor the total timing at all, the reason the timing reads 20 degrees after a higher rpm spin is because the car is idling fairly high still, causing more mechanical advance to come in due to the light springs. Am I right here? Is it a problem to run the light springs? When I had the light springs in there, I had no problems at all, and I felt the performance was much improved over the heavy springs, as with them, there seems to be a little to much lag for my taste.

Anyway, any comments/opinions are appreciated.

Thanks
Dave
 

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The light springs are usually TOO light. The problem is that they aren't heavy enough to pull the weights back in. The reason your RPM's are taking so long to drop, is because your timing is taking too long to retard back to initial, not the other way around.

I didn't experience an eratic idle, like you (and most people that I've talked to) in running the lighter springs, but I was getting pinging. I went down 2 steps (2 light blue springs), and now with my carb jetted bigger, I may try going back up at least to one light silver and one light blue.

Personally, I wouldn't go all the way down to the 2 heavy silver springs. If you look at the MSD charts, if you're running more than 20 deg. advance, you wouldn't get full advance until almost 4k.

I would run the lightest springs you can without effecting idle. When you get off the accelerator, though, the idle should drop back to your curb idle immediately (obviously I'm talking about if it's sitting in the garage, and not coasting back down to a stop on the street).
 

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Discussion Starter #3
I am currently running the two light blue springs, but I do not like them near as much as the light silver ones. As far as the idle goes, the strange thing is that the RPMs are not usually affected that much. The idle is sometimes higher by a bit (100 rpm at the most), but it is the timing that seems to change, and I don't know why. I will have to get the timing light back out and see just how much it really does change and how often, because maybe it was just a strange incident.

Dave
 

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10 degrees of initial advance would have far more effect on the idle than 100 RPMs. Because of this, I'm a bit confused. Are you saying that with the 2 light springs in there, the idle drops back to the same idle, even though the timing is still hovering in the 20 BTDC range?

Also make sure your "liking the lighter springs" is not just a "psychological thing". I could have sworn my car was faster after replacing the Pertronix Flamethrower coil with the MSD Blaster II. The time slip from the track, though, didn't agree though.

I could not tell any difference in performance with the 2 light silver springs and the 2 light blue springs. As soon as I get my track-lok fixed, though, I'll be taking my distributor calibration kit with me to the track to see if it does make a difference.

You could compromise and put one light blue, one light silver spring on. Maybe that will be enough to have your weights come back in, and will still have your timing in before 3k.
 

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Discussion Starter #5
Yeah, that is what I am saying, although it seems very strange. The idle will almost always return to very close to where I set it, 600 in D, and 850 or so in P. However, when we had the timing gun out, it read about 10 degrees more advance after a spin, but like I said, I will get it back out and verify that as soon as possible. My guess is that once the springs are opened up by the higher rpms, they wont bring the weights back in, so the extra timing would be mechanical advance then would it not?

My liking of the lighter springs is based on a lag, or hesitation the car seems to have with the heavier springs in there. I have tried one light blue and one light silver, and also two light blues, and with both, there seems to be a bit of a hesitation, whereas with the light springs, the car winds up smoother in my opinion. I cannot verify this by track times however, but as soon as I can get it back on the road, perhaps I will do just that.

Thanks
Dave
 
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