Steven, I started a new thread for the topic on your mileage here.
You might also check something that seems obvious but I think I figured it out on mine this week. Last week when the alternator went out, I checked the battery when I got home and it was just over 11 volts. Of course, I had driven it 40 miles or so without being charged, so it was draining a little as I drove it.
After I put the new alternator in, the battery voltage is now 13.5 volts, and steady at that whether the headlights are on or not, so I believe the regulator is doing it's job, otherwise, it would dip below 13 volts if it wasn't with a load.
Long story short, check the battery voltage when running, as that will impact your HEI distributor module if it doesn't have a full 12V to operate on (you can check the voltage at the HEI module pin too, but the battery is easier), resulting in less spark, resulting in less engine efficiency, resulting in sucky gas mileage because you have to give it more throttle to go.
All I can say is after changing the alternator this week, the engine seems more responsive, and I know I used WAY less gas yesterday. I only used a quarter tank of gas from Rosemount to Fridley to Ham Lake and back to Route 65 after the cruise. This was on par with my buddies '10 Camaro, and I think I even have a smaller tank.
Sometimes it's the simple things, and not always mechanically related and can be electrical in nature. Something quick and easy to check with a voltmeter.
John D said
Sep 28, 2014
Along those lines, using HEI on a points car there's a very important "mod" that needs to be done - removal/replacement/bypassing the original coil feed wire (resistive) with a 14ga or better supply wire.
Originally the cars came with a "resistor" wire to cut the voltage down to around 9v to save the points. There was a wire off the starter solenoid that gave full 12+V during cranking/start for the extra zap needed, but during run the coil got +/- 9v. (Chrysler & Ford used a ballast resistor).
Steven, I started a new thread for the topic on your mileage here.
You might also check something that seems obvious but I think I figured it out on mine this week. Last week when the alternator went out, I checked the battery when I got home and it was just over 11 volts. Of course, I had driven it 40 miles or so without being charged, so it was draining a little as I drove it.
After I put the new alternator in, the battery voltage is now 13.5 volts, and steady at that whether the headlights are on or not, so I believe the regulator is doing it's job, otherwise, it would dip below 13 volts if it wasn't with a load.
Long story short, check the battery voltage when running, as that will impact your HEI distributor module if it doesn't have a full 12V to operate on (you can check the voltage at the HEI module pin too, but the battery is easier), resulting in less spark, resulting in less engine efficiency, resulting in sucky gas mileage because you have to give it more throttle to go.
All I can say is after changing the alternator this week, the engine seems more responsive, and I know I used WAY less gas yesterday. I only used a quarter tank of gas from Rosemount to Fridley to Ham Lake and back to Route 65 after the cruise. This was on par with my buddies '10 Camaro, and I think I even have a smaller tank.
Sometimes it's the simple things, and not always mechanically related and can be electrical in nature. Something quick and easy to check with a voltmeter.
Along those lines, using HEI on a points car there's a very important "mod" that needs to be done - removal/replacement/bypassing the original coil feed wire (resistive) with a 14ga or better supply wire.
Originally the cars came with a "resistor" wire to cut the voltage down to around 9v to save the points. There was a wire off the starter solenoid that gave full 12+V during cranking/start for the extra zap needed, but during run the coil got +/- 9v. (Chrysler & Ford used a ballast resistor).
If your HEI is being fed by the original (cloth covered, white/red stripe) coil feed wire you are not getting full voltage. Click here for a '65 engine wiring diagram