MSD voltage?
 

So I pulled out my dui small bodied hei and replaced it with a msd 8528 RTR dist. Also installed 8.5mm FAST wires at 25 ohms. Using the same coil Flamethrower. 18 degree advance bushing and a medium and a light spring that at the moment is totaling too early(around 2200) so i will put 2 mediums in and try it. 32 total. Reading around 14 initial.Anyways i went out to try it and now if you punch it while cruising slowly in 1st it will roll the tires some and wont break them loose at all cruising in 2nd and go WOT. With the DUI dist it would blow the tires away cruising in 1st or 2nd gear and just floor it. Doesnt skip or miss while running through the gears. It does seem to run a little rougher initially when you first start it . Checking voltage Ive got 12.2 at the batt with key on and 11.77 at + side of coil. Running Ive got 14.5 volts at the battery and 12.65 volts at the + side of coil. Will it run right with these voltages?

There instruction sheet calls for 12 volts so it should be fine.

So I'm not supposed to have 14 volts at the positive side of coil if I've got 14 volts at the battery when running.

I changed to 2 blue springs now it totals at 2500 ...just like the chart says.

If I check all the fuses in the fuse panel when running I'm getting like 14.3 right now. But only 12.5 when running at the + coil / ignition wire. I would think that voltage would be the same at 14.3. Didn't know if the wire I'm using that goes from ignition to + coil has got some resistance

It needs a minimum of 12 volts, but 14.5 is starting to get a little high in terms of boiling out the Battery.

You should have close to same voltage at the battery and the coil. With your voltage drop it makes me think there is a resistance wire still in place.

My first msd distributor and reading about them it seems like they can be finicky about voltage. Didn't know if the running voltage isn't where it's supposed to be that would cause the possible feel of loss of low end power.

I second the suggestion of the resistive wire still in place. MSD instructions tell you to bypass the resistive wire where it is going into their box. The voltage will be there, but when it is drawing current it will drop. Find that wire and bypass it.

1. Put the DUI back in. Clearly it works better.

2. Why would the MSD need more voltage than the "small-bodied HEI"? Especially when using the same coil.

3. 12.2 at the battery with key on seems far too low. I'd expect 12.5 or better. What's wrong with your battery/charging system? Or do you have a high electrical load when the key is on? I'd be looking for 12.6--12.7 with the key off--no load.

its a RTR and not using a box. I think way back it had a certain length of silver resistance wire for the points. I think i cut it off and added copper wire many years ago but not certain. I cut back in to the original copper wire today and theres not much to it. I added 12 gauge to extend it over to the coil. Basically just put it back the way it was for years.

The pic is the original wire coming out of the harness next to the firewall. I wanted to see what type of metal it was. I believe originally the resistance wire was hooked to this.

I've got 3 gauges in the car that light up when you turn the key on. Maybe I didn't have the right voltage before and the msd is more sensitive...I don't know. As I ran the car the batt sitting voltage came up some and the running volts went down a little. Like youd expect.
Im going to try working with it some more and If it doesnt respond I will throw the dui back in and see if the punch comes back. its not like it lost a bunch of power. But it did go from lighting up the tires by just punching the throttle rolling in 2nd to not even a squeak now.

That's not much of a load...but test with the key off and see what happens.

I'd adjust the MSD to provide the same timing curve as the DUI, and see what happens. If you're still shy on power, reinstall the DUI and see if it comes back.

MAYBE you've got some other issue(s) unrelated to the distributor.

If in doubt for correct voltage/power to the HEI/DUI/MSD install a single relay and use the ignition lead to control the relay.
On relay post 30 to the battery via 15 amp fuse, post 85 ground, post 86 ignition lead and post 87 to + on coil.

Stretching here but you said it was running a tad rough after all your changes. Got a couple plug wires crossed or one cylinder not getting fire? You’d be surprised how well a Pontiac will still run minus a cylinder….

That’s the problem with doing a few things at once…. chasing ghosts…. Gotta be something relatively simple.

Depending on what if any wires are crossed it may not even back fire, just run like a turd!

The roughness I spoke of was the 1st 5 seconds of a cold start. It seems to struggle in that time compared to the dui dist. Once warmed up you dont notice it when you start it. Im going to try the things mentioned before I pull the dist and try the dui again.

No, it will NOT run right with these voltages.
You need to have the same voltage at coil as you have at the battery.
Lower voltage at coil indicates the use of a resistor in harness.
HEI/DUI/MSD do NOT use a resistor in harness.

Again, install a single relay and use the original ignition lead to control the relay.
On relay post 30 to the battery via 15 amp fuse, post 85 ground, post 86 ignition lead and post 87 to + on coil.

Now you´ll have full voltage to the coil.

Thats my next step,,,going to napa and see if they have that relay. Even if it doesnt help the msd Ill leave it there if I use the dui again.

To Whom It May Concern
 

IGN-1/RUN/Resistance wire, is under the dash on this car, Not under the hood.

IGN-1 and IGN-2 run from the ignition switch to the firewall connector and come together in one terminal. Then it has a single wire under the hood from firewall connector to the coil.

Clay

Correct! And that´s the wire to use for post 86 on relay.

What msd wants. So the pic of the wire in post 9 shows the wire that goes to the + coil post. I'm assuming going by msd pic that this wire will now hook to terminal 85 in their pic? I couldn't find a relay at napa so I just ordered a msd 8961 relay through Amazon they recommended. Be a couple of days.