HEI hot wire connection voltage question.
Thread Starter
Melting Slicks
Joined: Aug 2005
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From: Working on the car NY
HEI hot wire connection voltage question.
I have my HEI powered from an unused switched wire connector from the fuse panel. It gives full 12v+ reading when the ignition is turned on. It drops to 9V when it goes to crank mode. Is this OK or is there a better connection that will give a full 12V reading when the starter is cranked? I've developed a hard cold start condition now that the temp has dropped and am wondering if this is the reason why. Thanks
Race Director
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
no that is not the reason for your cold start problem. i have never measured that voltage when cranking but that sounds normal to me. In fact with the old points systems they were made to run at about that voltage (9.6v) using a ballast resistor, and the ballast resistor was bypassed at cranking giving basically the same voltage as you have now. HEI systems will run on very low voltage. your problem is some where else. although this is a good time to check all grounds.
Thread Starter
Melting Slicks
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From: Working on the car NY
understand what you mean by "replace that resistance with non-resistance." Could you further simplify?
Race Director
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
the old point systems used a high resistance circuit as the ballast resistor and had two circuits going to the solenoid one with the ballast circuit and one that bypassed it. you dont have this....that voltage sounds good to me and is not your problem. all cars drop voltage when they are cranking.
Thread Starter
Melting Slicks
Joined: Aug 2005
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From: Working on the car NY
no that is not the reason for your cold start problem. i have never measured that voltage when cranking but that sounds normal to me. In fact with the old points systems they were made to run at about that voltage (9.6v) using a ballast resistor, and the ballast resistor was bypassed at cranking giving basically the same voltage as you have now. HEI systems will run on very low voltage. your problem is some where else. although this is a good time to check all grounds.
Race Director
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
is this a stock Chevy HEI? if so its not picky the higher voltages are good but these things will run on really low voltage. you can go to the alternator/batt feed for power as a test this will give you a direct connection to the battery and may not drop voltage as much. i dont think this is your problem
Tech Contributor
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Make sure it's a non-resistive wire feeding the B+ terminal.
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Thread Starter
Melting Slicks
Joined: Aug 2005
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From: Working on the car NY
is this a stock Chevy HEI? if so its not picky the higher voltages are good but these things will run on really low voltage. you can go to the alternator/batt feed for power as a test this will give you a direct connection to the battery and may not drop voltage as much. i dont think this is your problem
Last edited by TWINRAY; Nov 19, 2012 at 11:05 AM.
Race Director
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
that should be ok, you can try moving the lead to the alt/batt feed post and see if that helps. i do not believe your cold starting problem is related to the voltage drop. basically if you have enough juice to crank the car you have enough juice to fire the stock HEI. if it helps, then you can set up a relay that switches on from your fuse panel wire and then feeds the coil from the alt/batt post.
Race Director
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
I will try this connection and will verify with the multimeter the cranking voltage of the feed. It's a new ZZ4 install that was starting ok but now it's not. I haven't tried it lately but with the temp drop, thought it may be the problem with it not receiving a full 12v when cranked. My other thought is something went wrong in the carb (needle/seat maybe??) that I rebuilt.
ok lets fill up the carb from the overflow vent to make sure you have gas in the float bowl....if it starts and then dies you know its in your needle set up. what kind of carb?
Le Mans Master
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Thread Starter
Melting Slicks
Joined: Aug 2005
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From: Working on the car NY
FWIW, what started me to this conclusion is I noticed my new Voltmeter install that reads 12V+ when the ignition is turned on and then drops completly far left when the ignition is cranked. When the car (does) starts, it goes right up to 14V 
.
.
Le Mans Master
Joined: Aug 2010
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Le Mans Master
Joined: Aug 2010
Posts: 9,272
Likes: 17
Thread Starter
Melting Slicks
Joined: Aug 2005
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From: Working on the car NY
http://www.google.com/url?sa=t&rct=j...WR55RRhdRCyvhg
hope this helps
hope this helps
To wire the system, the ballast resistor wire feeding the points-type coil needs to be removed and replaced with regular copper wire
Le Mans Master
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http://www.google.com/url?sa=t&rct=j...Em3RPmzJuOh-DA
good reading on all these links, hope it helps
there are very few absolutes with hei , but a constant 12 volts is one of them
your starter may be dragging or battery may not be spinning fast enough.
good reading on all these links, hope it helps
there are very few absolutes with hei , but a constant 12 volts is one of them
your starter may be dragging or battery may not be spinning fast enough.
Last edited by oldalaskaman; Nov 19, 2012 at 11:16 AM.
Thread Starter
Melting Slicks
Joined: Aug 2005
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From: Working on the car NY
The "white cloth covered" resistance wire or a lead from a "ballast resistor" must not be used to power a GM H.E.I. distributor.
I read that before and have it taped off and wired it independly.
I will try to find a connection that is 12V when cranked. Otherwise, the carb has to come off (again) for a look-see.
Thanks - it's now off to the garage
