Cool, thanks man!

 

With my engine running at idle, I was getting .53 volts at the +coil. It peaked at .94 volts at higher rpm's. Yeah, that sounded weird to me too, less than a volt. So I double-checked the MSD manual and it says that with the engine running, very high voltage will be present and no test equipment should be connected. Oops! Neither the meter nor ignition was harmed though, but I don't know why my meter showed such a low reading if there's really high voltage there? Is it because the coil is getting it's power from the MSD box, which is capacitive discharge, so maybe it's not getting a constant voltage for the meter to catch? Hmmmm, I dunno that one.

 

Hmmm, well get this. I called MSD tech support today and talked to them and they said I should be getting 470v on the coil's positive terminal. How am I supposed to get that at the pos terminal from a 12v source unless the box is already upping the voltage? I told him that I ran the coil and at idle I was getting 2v and then at WOT I was getting around 5-6v. I don't know if the guy knew what he was talking about as I had to explain to him a couple of times what and where I was taking voltage from. He was really nice but sounded pretty confused about what he was saying like as if he was questioning himself also.

That's really weird that you're getting that low of voltage. I would've thought 12v at the coil would be good and that the coil amplified it up to the 35 - 50+ k range depending on the coil.

I applied for an account at MSD's forums so if I get in I'll post my question. I didn't see it in their forum but I didn't get a whole lot of time for searching tonight. I switched back to my HEI setup with stock module and bypassed the box. It was getting late and I didn't want to be setting timing at 930 at night in my neighborhood and keeping people awake so I did the basics and I'll get back to it first thing when I get home tomorrow.

 

You gotta remember that the MSD doesn't operate like a conventional ignition. And the coil isn't powered by a 12 volt source like a stock ignition system is. You answered your own question too, the box does up the voltage.
Here's from the MSD manual:
CAPACITIVE DISCHARGE
"The MSD 6 Series Ignitions feature a capacitive discharge ignition design. The majority of stock ignition systems are inductive ignitions. In an inductive ignition, the coil must store and step up the voltage to maximum strength in between each firing. At higher rpm, since there is less time to charge the coil to full capacity, the voltage falls short of reaching maximum energy, which results in a loss of power or top end miss.
The MSD Ignition features a capacitor, which is quickly charged (within one millisecond) with 460 - 480 volts and stores it until the ignition is triggered. With the CD design, the voltage sent to the coil is always at full power even at high rpm."
So....I'm figuring that we're getting a low reading on the meter because it can't read such a high level when it's on a 12 volt setting. We both must be using good meters with fail-safe systems preventing them from frying. I would also have to guess that if you hooked up a light bulb type tester to the coil, it would get blown to smithereens!

 

Ha ha, I'll go stick my circuit tester on there right now!

Well I'm pretty sure my Fluke meter's rated to 600v but I'm not sure. I'll have to take a look when I get home. Like I said, I changed back over to HEI and I'll take it out for a spin when I get home. I'm beginning to think nothing is wrong with the box with your diagnosis coming up with the same thing as well.

 

logically if its discharging for only a millisecond then the gage will not have time to go from such a low volt reading to such a high volt reading.

 

It's quite possible. I referred to that a couple of responses ago when I said "Is it because the coil is getting it's power from the MSD box, which is capacitive discharge, so maybe it's not getting a constant voltage for the meter to catch?" Great minds think alike, I guess? Either that, or I gave you a subliminal plant!
I don't know what the reaction time on a test meter is, but it could be that's what's happening....or not happening!

 

So went with the stock HEI setup and it still does it so that's telling me it's something else. It wasn't as bad but that could just be that my timing's a little different and more conservative than with the MSD distributor. I'm not getting above 30 degrees of timing.

If I had wiped a lobe off the cam it would be doing it in park while revving right? Not just under load and while driving around?

 

I think I finally found what it was. I went out and did a test drive to see how it would do and it still did it. I was going to change out carbs if it still did it so when I got back I disconnected the carb and lifted it and there was slight vapor/liquid on the gasket on the passenger side... vacuum leak. Lifted the carb off, dumped the fuel and flipped the carb over. On the baseplate was some weird gunk that was was about 1/16th's of an inch wide and with no height at all. You could feel it if you ran your finger over it though and it ran from carb flange to venturi. It was as hard as a rock and I couldn't get it off with a brass brush so I just scraped it off with my knife and finished with the brass brush. Put on an older 1/4 inch Edelbrock soft spacer and took it out and it ran fine without any major problems. Now I just have to dial in the timing and the adjustable secondaries again and I should be good to go. Atleast I hope...

What's weird is I went around it with carb cleaner a couple of times looking for vacuum leaks and couldn't find any at all. Could the leak be sucking only on the high end for some reason?

 

Good you finally found it, because I was going to suggest dismantling the engine next and smashing all the pieces with a sledgehammer!
Did the "weird gunk" look like a dark gray/blackish corrosion in the aluminum? And it's quite possible that it wasn't bad enough to leak at idle, but the extra vacuum pull at higher rpm's was enough to let air get sucked past it. Was there any sort of a slight dip in the gasket?
I hate that, when the obvious things aren't obvious, even when you look for it.