GM 4 pin HEI to 8 Pin Hei conversion possible

ronsonol · Post by **ronsonol** » Sun May 28, 2006 8:48 pm

Thanks Lance for the explanation, I really appreciate the time you give.

The simple process of switching which wire goes to P or N, is what sets up which wires signals, and which wire grounds?

I'll give it a go this week as time permits,

Many thanks.

Bernard Fife · Post by **Bernard Fife** » Sun May 28, 2006 9:14 pm

The simple process of switching which wire goes to P or N, is what sets up which wires signals, and which wire grounds?

ronsonol,

Yes, it's that simple, and people who have troubles with erratic timing often cure them simply by reversing the wires.

Lance.

ronsonol · Post by **ronsonol** » Mon May 29, 2006 2:54 pm

Recap, MSII, v3, on code 2.672. Hei 7-pin in a SBC 350. Using Hall input as per HEI instructions to the letter. Was running tach from negative coil, followed step 50b, now for 7-pin HEI I cut the legs off C12, and C30, and jumpers D1, and D2. I left C12, C30 in place just not touching the leg I cut - is that OK?

Well, I got the base timing working around 13 degrees BTDC, the car starts and runs without the bypass voltage disconnected. With timing light, advance does not change regardless of RPM at around 13 degrees.

I should also mention, that the car will start with the bypass connected to, that seems to work, lets the car start fine where base timing is set, then it comes in after the car start to advance the spark.

I hook up the bypass voltage, and it stills run, and its apparent advance changes. Setup trigger offset, so timing light matched what MS wanted. seemed ok, around 30 degrees at idle.

Doesn't run well though. Ran better before when MS was just doing fuel. I am having shutdowns, and I logged the events, and you can see where MS sees RPM=0 at certain times.

Not sure which mod to try, if any the booster or the MS-extra mods.
Many thanks in advance,

Ron

ronsonol · Post by **ronsonol** » Tue May 30, 2006 5:27 pm

Update, I applied the MSnS-Extra input mods for the 7-pin HEI, and today I had no tach drops to 0.

It runs a little shaky, but that must mean I am at a good spot to start tuning the spark advance.

Lance, many thanks for all you help.

Maybe a little note could be added to the HEI docs, it would have helped me greatly this past weekend.

Bernard Fife · Post by **Bernard Fife** » Tue May 30, 2006 6:09 pm

Maybe a little note could be added to the HEI docs, it would have helped me greatly this past weekend.

ronsonol,

I'm glad you got it sorted.

Some people have had problems, many (including me) have not had problems. Whether this is an issue with tolerances, wiring, or something else, I don't know (yet!).

Right now, we're looking at three alternatives to the way the manual recommends setting up the input for the HEI:

- the MSnS-E mods <http://megasquirt.sourceforge.net/extra/setup-hei7.html>,
- the transistor mod (below),
- or using the VR circuit (I am currently experimenting with this).

If people who have used these circuits with the HEI 7 or 8 pin modules comment in this thread, that would be helpful. When we have enough comments to be able to choose the optimal method, I will change the manual.

In the meantime, I`ll write up a page that describes all three and link to it off the HEI pÃ¢ge.

Lance.

ronsonol · Post by **ronsonol** » Tue May 30, 2006 6:39 pm

Lance,
its a good idea to make the options available, as you are aware a few people have found some sucess with the MSnS-E mods here, and have already commented on such.

http://www.msefi.com/viewtopic.php?t=17 ... c&start=20

Take care,

Ron

Bernard Fife · Post by **Bernard Fife** » Tue May 30, 2006 9:36 pm

Ron,

I have added a rough Hall input options page here:

http://www.megamanual.com/ms2/inputHEI.htm

The MSnS-E mod is the simplest, but we really need to find out if it is the best, or if some people still have problems.

Lance.