MSefi.com read only forum (Jan.15,2018)

I have a '69 Chevy pickup with a 350 SBC I'm converting to TBI from carb. It has a Delco Remy distributor with vacuum advance. I'm a little confused about the generations of HEI distributors (probably how they work also) and if this will work with MSII given that what I've read says it has a 4-pin HEI module in the cap that isn't capable of being computer controlled. If the advance is managed with a vacuum signal how would I get the distributor to work with MSII and a 7-pin module. Does it have the internals to take advance timing from an external source?

-Steve

I have one from a '76 Chevy and I'm leaving it all original for upgrades from older GM points dizzies . I wouldn't try to convert it, but you could. I would get one from a later year GM V8 maybe in '86, and use that one instead, because it should have much better connector options, than the 4-pin HEI dizzy.
Jan

Or.... You can lock the vacuum/mechanical advance and install a 7 pin module in your 4 in unit. (you will need the little wiring harness to go inside the dizzy)

Or.... You can you can mount a 7 pin on a heat sink and mount it externally using the existing VR sensor pickup. (still need to lock it though!)

Or.... As Steve suggests, pick up a 7 pin at your local pick-n-pull. Be careful to make sure it's not worn out though!

Or.... You can buy rebuilt starting at about $100 or new units starting about $200


Lots of choices out there. Just depends on what you want to spend.

Ken

Thanks Gentlemen, I bought a SBC interchange manual this weekend with a pretty good explanation of the differences and the years involved and with your help I think I know what I need to now. I'll trot off down to the wrecking yard and grab some bits for mockup and testing. Looks like '85-'95 Chevy vehicles with K VIN code have the V8s with HEI distributors and the 7-pin modules. I'll need an external coil for this too, which I think I prefer over the coil in cap.

-Steve

Just curious....

Why not coil-in-cap? I have run them very successfully in the past.

Ken

kjones6039 wrote:Just curious....

Why not coil-in-cap? I have run them very successfully in the past.

Ken

No particular reason, other than it gives me options for more widely available external higher performance coils.

-Steve

I have a standard V2.2 MS1. No mods.

I decided I wanted to leave the ignition stuff as is until I've gotten the fuel side working so I tinkered some more to get the engine speed input working. I hooked the tach out from the 4-pin HEI (in the vac advanced dizzy) to the tach input on the relay board and in Tuner Studio I get the RPM reading but it is 2 times what my timing light says the actual RPM is. Is there a mod or something I need to get the tach signal correct?

-Steve

Sven wrote:I have a standard V2.2 MS1. No mods.

I decided I wanted to leave the ignition stuff as is until I've gotten the fuel side working so I tinkered some more to get the engine speed input working. I hooked the tach out from the 4-pin HEI (in the vac advanced dizzy) to the tach input on the relay board and in Tuner Studio I get the RPM reading but it is 2 times what my timing light says the actual RPM is. Is there a mod or something I need to get the tach signal correct?

-Steve

Are you using the white wire from the cap? I have run both 4&7 pin using the HEI tach output (without any mods) feeding a relay board and never had any issues like incorrect RPM. How is your MS jumpered?

I am curious...... How you are determining RPM using a timing light?

There are some HEI mods out there but I am not sure they apply to MSI. I will take a look when I get some time and post them.

Ken

kjones6039 wrote:Are you using the white wire from the cap? I have run both 4&7 pin using the HEI tach output (without any mods) feeding a relay board and never had any issues like incorrect RPM. How is your MS jumpered?

I am curious...... How you are determining RPM using a timing light?

There are some HEI mods out there but I am not sure they apply to MSI. I will take a look when I get some time and post them.

Ken

Thanks for your reply, Ken.

The dizzy cap has a 3 pin connector back into the lower body of the dizzy (for the pickup I presume) and two other pins. 1st of the other pins is labelled 'batt' and, obviously, is fed from a switchable 12v source. The other is labelled 'tach'. Yesterday I connected the pin labelled 'tach' directly to the relay board. It wasn't already connected as my truck doesn't have a tach. Now the 'engine speed' gauge on tuner studio reads about twice what the RPM reads on my digital timing light.

After your 'How is your MS jumpered' question, I am re-reading through the 'Assembling your Megasquirt' document and checking my MS1 because I built this unit quite some time ago and I'm not sure if I did the right things in terms of jumpering for the ignition input and resisters for the coolant temperature sender, which also reads very high.

-Steve

I went back over the build docs and my MS1 and I have the XG1-XG2 jumper in and the resisters are correct for my GM/Delco coolant sender model. Anyway, I'm not worried about the sender, I have a spare and this one might be bad. Looks like my MS1 is stock as per the build doc right out of the box.

I do have a oscilloscope, which I could put on the tach output from the dizzy and see what I'm getting, assuming the output won't burn up my scope.

-Steve

Rolled by O'Reilly today and looked at a couple distributors. The one I looked at was from a early 1990's Chevy truck with a V8 and the distributor had two wire sockets, one with 4 pins and one with 2 pins. Pic below.

Anyone know where to find information about this distributor and the module? Is this a 7-pin module? I wish I knew more and didn't need to ask such elementary questions, but searching the forum hasn't turned up anything I've found useful on this topic.



-Steve

I've done more digging and that distributor has the 8-pin module. I believe I would need to add a MSII to my V2.2 MS1 and use MS2-Extra!

I guess I can give up on the dizzy I have (4-pin module with vac adv) and just move on. Kinda wished I could do the fuel without the ignition, but I'm missing how to configure my 4-pin module dizzy to provide a signal to the MS that isn't double the actual RPM. I guess using an external coil with the 8-pin module dizzy will give me a standard signal to the MS, I just won't have advance initially, at least. Maybe I'll do ignition first ...

Now I'm enlightened I have something to go on ...

-Steve

From the manual:

* 4 pin module - electronic ignition, but doesn't do computer timing control, top left
* 7 pin module (large) - electronic module that does timing control, used with coil-in-cap distributors, top right
* 7 pin module (small) - electronic module that does timing control, used with some external coil distributors, bottom right
* 8 pin module - electronic module that does timing control, used with most V8 external coil distributors, bottom left
* 5 pin module - rare and not discussed here. not shown

Thanks Ken, I think I just found the same answer in the same place, something I can use ...

Now to make some orders for parts ...

-Steve