72 starting issue

[Jmoney01]

Ok, I have been slowly working on my 72. I installed a set of aluminum zz4 heads. Now, after I put it all back together, it won't start. It cranks over really good. I have power to the new coil, cap,
Module, etc (hei). But it's not firing. Thought maybe it is a ground issue because of the aluminum heads?? Also, related or not, the purple wire to the starter is getting hot (smoking) with the key in the on position. Everything is hooked up as before I did head swap. I'm stuck. Any help would be great.

[kidatheart]

I have made this mistake, so I will ask-you put the rotor back in the distributor, right? I left it out once....
Did you crank it and make sure the rotor is turning?

[Jmoney01]

Lol. I had to double check myself. Yes. Installed and spins

[AussieinNC]

Did you install the distributor correctly, in relation to the firing order?

Did you over tighten the rockers and they are holding valves off their seats?

What compression pressures do you have?

Pull cyl 1 spark plug, place your thumb over the spark plug hole and have an assistant tap the ignition, until you feel pressure on the plug. Then by hand, bring the mark on the balancer up to align with the timing tab on the front cover.

Remove the dist cap and look where the rotor is pointing. It should be pointing to the cylinder 1 post on the dist cap....if its not, you have found your issue.

Correct way to fix it is pull distributor and align correctly, some people just move the leads around on the cap....

Let us know how you go.

[Steeveedee]

If the purple wire is getting hot in the "ON" position, you have wired the ignition switch wrong. The purple wire goes to the "S" terminal on the starter and only should be powered during cranking. Given that, I suspect that the red and purple wires might be switched on the ignition switch. Are you certain that you didn't change anything else when doing the swap? Also, aluminum carries current better than iron, so that is not the problem.

How are you getting power to the HEI? Did it have an HEI before you did the head installation?

[Jmoney01]

I will triple check that I'm not 180 out. The hei has been onfor 25 years. Using a test light, I have power to the coil. Even if I was out 180, the coil should still fire, correct? I will check the starter wire tomorrow. I did change the power to the hei from the terminal off the starter to a wire out of the block that turns on with ignition

[Fbks_Cruiser]

Originally Posted by Jmoney01

I did change the power to the hei from the terminal off the starter to a wire out of the block that turns on with ignition

What wire are you using from the block on the firewall? If it was the wire that powered the original coil, this may be your problem as it is a resistance wire and drops the voltage ( if you look closely at the insulation it actually says “resistance” on it). If you are not using the resistance wire, but simply picking up power at that terminal on the firewall you are okay. Get a multimeter and check actual voltage at the connection on your distributor to verify it is 12V. Test light won’t tell you that.
That purple wire should only have power when the key is in the start position. In run position it should have 0V.

[67 twins]

Originally Posted by Jmoney01

I will triple check that I'm not 180 out. The hei has been onfor 25 years. Using a test light, I have power to the coil. Even if I was out 180, the coil should still fire, correct? I will check the starter wire tomorrow. I did change the power to the hei from the terminal off the starter to a wire out of the block that turns on with ignition

You stated that took power from the fuse block that has power when the ignition is on, but are you certain it has power in the start position. It may not & you know if it doesn't it's not going to start

[Jmoney01]

When I verify the purple wire to the starter terminal I will go back to the original setup of feeding the coil from the starter. Was just trying to stop burning the wire on the headers. Will work on it Saturday

[rpmerf]

Spark, Fuel, Compression.

I assume you have a timing light. Put it on a plug wire while cranking to see if it is sparking. If not, work your way back.

Dump a small bit of gas in the carb. If this gets it to start, you are not getting fuel.

Use a compression tester to check compression. You should be able to hear the starter compressing the different cylinders as it spins.

I've heard of people leaving rags in the intake ports before.

[Jmoney01]

Checked some things tonight. Purple starter wire sending 8.8 volts and shuts off at starter when key not in start position. Coil is receiving a constant 12 volts when key is on. Changed plug wires around 180 and no different. I'm still not getting spark at the spark plug. I will check compression tomorrow. Also, I confirmed the dizzy is spinning

[Bobbysgmc]

Check to see if you got the purple wire caught between intake,valve covers head and block or pinched between something else.

[AussieinNC]

The HEI unit has two spade terminals...
one to power the coil
one as feed for the tachometer.....
Make sure its on the correct one

Make up a small jumper lead with a female spade terminal on one end and a small alligator clip on the other...

Remove the Ign feed wire on coil and making sure you are connecting to the coil terminal, install the other end of the jumper wire to battery....try and start and check for spark....if it now works, you have an issue with the ign wiring between switch and HEI unit.

If still no spark, replace the ign module and try the test again....

Finally, make sure there is a ground strap between the engine and the cab...

See attached image showing old wiring against new wiring...