Where is the best place to tap into a switched 12V source for the 6A box? It is mounted on the pass side inner fender. Would the R terminal on the solenoid be a good location, or do I need to tap into the ignition wiring?

TIA, Kevin

R terminal on the solenoid is only hot while cranking, I assume you'd like it to keep running after you release the key :D so that won't work. IGN terminal on the fuse block is the best source, not the closest but usually the best.

Doesn't the 70 have an Idle Stop Solenoid wire? If so that would work.

John, I have no idea what an idle stop solenoid is. Hank, how would I connect the lead to the ign terminal on the fuse block? Do I have to make a hole in the firewall?

Thanks, Kevin

I don't know if factory did, I would have to look in the assembly manual. My car has a non-stock intake and carb so I don't have an idle solenoid. Maybe that wire is being used for the electric choke on mine? Also is that wire heavy enough? I'm not sure what gauge it is but most HEIs call for, I think, a 12 gauge wire.

Also is that wire heavy enough? I'm not sure what gauge it is but most HEIs call for, I think, a 12 gauge wire.
Good point. It's kinda light for that purpose.

One other thought, along with getting clean power to that unit, you need to insure you have a good solid ground for that box.

Do a search on the forum and you'll find this advice given multiple times. :)

I am going to connect the ground to the engine block, where the battery is grounded. Does that sound like a good plan? I still need to know where I can connect the 12V lead. I did a search in this forum and did not find the answer I was looking for. I'll try again with a different search criteria.

Kevin I missed your earlier question. Try this link there are several suggestions.

http://www.chevelles.com/forums/showthread.php?t=84124

Kevin,

It seems like we're not being very much help, let me try again.

I would run a lenght of #12 wire from an ignition switched tap on the fuse block, to the MSD box. You shouldn't have to drill a hole in the firewall as there are plenty of plugs or gromets you should be albe to sneak the wire through. If a tap of the properly fused value (probably 20 amps) tap isn't available, run a #12 wire off the ignition switch through an in-line fuse to the MSD box. I personally don't care for fuseable links.

As for the ground, I suggest running a #12 ground wire from a mounting bolt/screw of the box to the fender, to the point of contact of the small black wire runnning off the negative battery clamp to the inner fender well or core support. This ground point lends itself to the pairing up connectors. Lastly, you could run it directly to the negative battery terminal clamp. Just use the proper size terminal to allow it to be secured to the clamp bolt. This is done on many cars today. I wouldn't recommend attaching it to the engine block ground cable connection. That connection is "sacred" and shouldn't be burdened with other connectors which may cause it to loose integrity.

On the subject of grounds......
I personally like to see a length of wire with terminal ends run from the engine block to the frame, usually from a bolt of the engine side motor mount to a bolt of the frame side of the motor mount. This insures that engine is properly grounded to the frame. A similar wire run discretely from the frame to the inner fender will insure the body is properly grounded also. However, unless these connections are solid and clean, they're no better than a dirty battery cable connection.

Then there's always those little gound straps for "radio noise suppresion" that go from the firewall to the block... I'll let others discuss these.

Just keep in mind that good grounds are as essential as a good power connection. One is useless without the other. However, a poor ground is extremely hard to troubleshoot or locate and will (and has) caused more electrical troubles and intermittant performance than most people realize. Minutes spent making solid clean ground connections will save you hours of frustration and dollars later on.

I'm sure that's more than you wanted to know but maybe you got an answer in all this dribble. I just know an often stated prblem with MSD boxes is intermittant performance due to poor grounds.

Actually Herb I thought I was being helpful. The link I provided suggested some good ways to hook up an HEI, particulary using the ign terminal in the fuse block as John mentions and which I mentioned above along with a link to a supplier for a cable with the necessary spade lugs attached.

Where is the best place to tap into a switched 12V source for the 6A box? It is mounted on the pass side inner fender. Would the R terminal on the solenoid be a good location, or do I need to tap into the ignition wiring?

TIA, Kevin

You could mount it to the same point as the HEI lead but you need to run a seperate line to the 6A box from the power source.

Well the MSD 6A is a hi-energy output coil. Yes it is more than that and no it is not a complete HEI ignition in itself. Still it needs a switched source with roughly the same current capacity as an HEI igntion so I thought the other answers were appropriate.

ok

I am going to connect the ground to the engine block, where the battery is grounded. Does that sound like a good plan? .............

You couldn't ask for a better ground than that.

One point to add here is that the bulkhead connector is not totally populated. It is very possible to get the special terminals used and add new/additional wires to the bulkhead. That way you run your wires just like the factory did. There are a number of sources but I got my stuff from American Autowire.

For the switched ignition input to an MSD box you can use the original resistor wire that was connected to the + coil terminal. The switched input is used to switch on the MSD there is no current load on that input. The MSD box has a separate power input that is hot all the time, often connected directly to the battery or other like the horn relay, that supplies the current for the ignition system.

Rermove the original resistor wire fron the engine side of the bulkhead connector and runa new wire of the proper size up from there. I did this on the last one instead of running from the inside.