[Formulajones]

Originally Posted by MarkS57

Yup, before I went with the new Ames (M&H I believe) harness, this is what I was going to do. A small box to enclose an automotive quality 40A relay with a terminal strip to connect the original coil lead, tach lead, and the 12 AWG 12V power lead. The relay with cause no noticeable voltage drop across the resistance wire. This way you keep all the original wiring. I decide against this as I've read in other posts that the external regulator of the original alternator can potentially cause HEI failures. Not sure about that but as I needed to increase my alternator current capacity anyway, I went for the engine harness that is configured for HEI & the SI alternator. Its been a great set up.

Now, something else about the HEI, you may find issues with modern radios that have a USB interface for your phone, Ipod etc. I did, it took wiring separate grounds, power leads and a lot of ferrite beads on the USB radio cables to fix the problems.

Interesting on the ferrite beads. I looked them up and they are very short clip on things. Do you have to buy a bunch of them to cover the entire length of your USB cables, or just one clip on ferrite bead does the whole cable???

[MarkS57]

Originally Posted by Formulajones

Interesting on the ferrite beads. I looked them up and they are very short clip on things. Do you have to buy a bunch of them to cover the entire length of your USB cables, or just one clip on ferrite bead does the whole cable???

I covered a lot of the USB cable you cannot see. Left the cable uncovered that's visible running down the mount to my old Ipod Touch. Without the modifications outlined, the operation of my Ipod was a real s**t show. FWIW, also read that too much ignition advance can make things worse with the HEI interference, no idea about that.

[Formulajones]

Originally Posted by MarkS57

I covered a lot of the USB cable you cannot see. Left the cable uncovered that's visible running down the mount to my old Ipod Touch. Without the modifications outlined, the operation of my Ipod was a real s**t show. FWIW, also read that too much ignition advance can make things worse with the HEI interference, no idea about that.

Interesting. I was looking them up and they are pretty cheap to buy.

I don't have RFI issues at the moment but have been watching for solutions just in case.

[thebrat1967]

Originally Posted by Entropy11

I have always just run it this way.

Hi I like your diagram but have 1 question. the 2 wires that go to the original coil, 1 is the resistance wire and other is positive from the started so I can tape off or remove the hot wire and just put the resistance wire on terminal 86 and just use the fused wire from the battery in place of the wire I remove from the starter correct?

[lust4speed]

On later engines Pontiac used a circuit off the solenoid to supply power to the coil when ignition switch was turned to the start position, You have two choices - leave the wire from solenoid to coil in place and only add the resistance wire to the relay, or you can take both resistance wire and the wire from solenoid together to energize the relay.

[Schurkey]

Originally Posted by FirebirdHank

OK, so I'm using the stock coil wire right now (GM type aftermarket coil in cap). I checked it and it shows full 12 volts. The car runs fine. Am I asking for problems?

Yes.

You MUST check for voltage when there is current flow. No resistor will drop the voltage until current flows. When current flows, you'll find about eight volts. You will not get full power potential from the ignition coil when it runs off of eight volts instead of thirteen-plus.

The HEI is designed to draw a huge amount of power through the ignition coil, intentionally limited by circuitry in the ignition module. When starved for voltage, the module increases the dwell time to compensate. But that "uses up" all the available dwell-time, leaving no additional for higher-RPM operation.

Originally Posted by lust4speed

The HEI is a sneaky sort of current hog and if you have the proper instrumentation you will observe a massive but imperceptibly short burst of current generated at each ignition pulse.

THANK YOU. Not many folks understand this.

AVERAGE amperage draw of an HEI is very reasonable. PEAK amperage is quite high. In other words, the HEI needs pulses of power, and the wire gauge has to be sized to allow the peaks, not just the average.

[Lee]

Did not read all the replies.

Has anyone mentioned that the HEI will, most likely, require hammering the sh!t out of the firewall in order to physically fit in a '67? And even then, the wire boots may still be rubbing.

In my old '67, I swapped out the HEI installed by a previous owner for a Small Body from Dave (www.davessmallbodyheis.com) . I wasn't convinced that the HEI wasn't getting tweaked when the moved under WOT.

[Hotrodjohn71]

I was able to install an HEI on our 67 FB, but there is no room for error. Ours has a stock 326 with stock motor mounts. The only way for ours is to point the vac cannister towards the pass side.. There should be just enough rotation to dial in your timing.

I had read that they would need to have the firewall hammered in to fit, or they just wouldn't fit at all, but I must he blessed.

The HEI is great. Reliable and kicks a great spark. Only downside is originality.

I run 12v relayed power to mine also.

[Entropy11]

Originally Posted by thebrat1967

Hi I like your diagram but have 1 question. the 2 wires that go to the original coil, 1 is the resistance wire and other is positive from the started so I can tape off or remove the hot wire and just put the resistance wire on terminal 86 and just use the fused wire from the battery in place of the wire I remove from the starter correct?

The original resistance wire (7-9v) and the bypass wire (12v) both were originally used for 2 separate tasks. 12v bypass only gave 12v during the start sequence and resistance is what maintained voltage when the key was returned from “start” to “run”.

You can start by feeding terminal 86 with the resistance feed and the bypass feed. You could possibly terminate the bypass feed to it and try that too. I can’t remember if all vehicles keep the resistance feed alive while the ignition is in the start position or if they sometimes just tie bypass to “start” and then engage resistance wire in the “run” position. There’s a note about it in the bottom left of the diagram.