Hei distributor timing - JeepForum.com
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post #1 of 8 Old 06-18-2021, 11:31 PM Thread Starter
EmilianoL
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Hei distributor timing

Hey y’all I have two questions I’m going to put my hei distributor in my 1990 4.2 L yj and was wondering if the butter bypass will affect the hei distributor in anyway? And two what to set the timing to when I put my hei distributor in I’ve heard 8 degrees but I’m not sure and also I’m not sure if the nutter bypass will affect that as well.

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post #2 of 8 Old 06-19-2021, 02:07 AM
timatoe
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The Nutter Bypass has no bearing on the HEI since the HEI is going to be the ignition system, the ECU and ICM are no longer doing anything. Stock timing I believe was 8* mine seemed to stumble at 8* with the HEI I had to set it to about 12-13* BTDC to get it where it seems to run the best.

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post #3 of 8 Old 06-19-2021, 10:38 AM
gehlsurf
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As Timatoe noted, Nutter bypass is ok, my 89 YJ has a bypass and a DUI dizzy.

Carb is a Weber 38/38 and previously had a 32/36, both ran well with the timing at 12°. 12° is what the gentleman at the DUI (I forgot the real name of the company, but you can search it easily) told me set it too. Also, gap spark plugs, I think I did .04, because supposedly you are doing a Team Rush Mod with a new high power Distributor.
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post #4 of 8 Old 06-19-2021, 11:15 AM
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Are you using a stock GM HEI or one already prepped for the 258? The distributor gear must be changed out if you have a GM unit. The aftermarket models have already done that.
An .040 - .045 gap with standard copper plugs is used as well.
The Nutter is gone as the HEI is a one wire, non-computer hook-up.
12* is a good ballpark for the improved spark. (I run 14*)
Davis Unified (DUI) supplies a 1970 Camaro/Corvette vacuum can with their unit. Other HEI's may not.
If your wires are old, carbon-core, or smaller than 6.5mm you may want to go to a 7 or 8mm set. Spiral wound core works the best, but isn't cheap.

Once you do the install...run the motor in the dark after you have adjusted to your night vision and see if there is any arcing to the block or manifold, etc. HEI often leaks voltage if your wires aren't good enough.
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post #5 of 8 Old 06-19-2021, 01:29 PM
timatoe
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That's a good mention on the spark plug wires, you do need larger core wires than the stock ones. FYI, a 1980 Ford Fairmount with an inline 6 came stock with 8mm wires and they fit the 4.2 very nicely. (and cheap)

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post #6 of 8 Old 06-20-2021, 08:08 AM Thread Starter
EmilianoL
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I’m using one that’s already prepped for the 4.2 L so I don’t need to worry about the fear however I may change out the wiring to 12 gauge for the hei
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post #7 of 8 Old 06-20-2021, 08:46 AM Thread Starter
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Also would I set the timing to 8 degrees after I put the distributor in there from tdc
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post #8 of 8 Old 06-20-2021, 09:43 AM
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Quote:
Originally Posted by EmilianoL View Post
Also would I set the timing to 8 degrees after I put the distributor in there from tdc
I would suggest you try 8, 10, and 12. Drive a little at each setting and let vehicle tell you what it likes best.
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