HEI plug gap
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Cross-Country
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HEI plug gap
I wasn't able to find any posts about this. I have a 84 f150 with a 300 I put a HEI distributor on it and im trying to figure out what gap I should use. I know the HEI system is a lot stronger allowing for a wider gap but the distributor didn't come with any information about it. The stock gap is around .044 I have it set to .062 now and I'm wondering if I can go wider. Also maybe there's a better plug that will help get the full power from the new system.
FTE Legend
Joined: Nov 2015
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From: Angier, NC
Set it to stock gap.
The HEI is no hotter than the Ford DS II system.
IIRC when HEI first came out the plug gap was pretty big like around .060.
They had problems where the spark would burn thru the rotor or something like that under the cap.
Dix was smaller plug gap.
Dave ----
The HEI is no hotter than the Ford DS II system.
IIRC when HEI first came out the plug gap was pretty big like around .060.
They had problems where the spark would burn thru the rotor or something like that under the cap.
Dix was smaller plug gap.
Dave ----
FTE Legend
Joined: Nov 2015
Posts: 30,935
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From: Angier, NC
Thing is a lean mix is hard to light off to start with and think with the wider gap it would help.
I was just getting out of trade school when this all happened and was only for a few years IIRC.
Dave ----
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From: Virginia
Just like tires, batteries, etc. everything is a compromise. A wider gap does help the engine, giving it a hotter spark. But if the gap is too wide it will create a misfire. The factory gap spec was a compromise, life of the plug versus performance. .044 gap will give you decent performance, and very long life. With a iridium plug you will get over 100,000 miles on a set of plugs if the engine doesn't burn oil. You can get better performance by widening the gap, but you will need to change the plugs more often to prevent misfires. So if you do not mind experimenting, you could see some gains by widening the gap, but you may have to change the plugs on a more frequent schedule.
FTE Legend
Joined: Nov 2015
Posts: 30,935
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From: Angier, NC
When running a wider gap it takes more power to "push" the spark and like water will find the easy path to ground.
So if the wires are a little weak they could leak spark to ground and cause a miss fire.
I have seen bad plug wires cause the spark to jump from the coil tower to the neg side of the coil.
Had it happen on my 02 Durango more than once till I told the dealer to change the plug wires.
Remember the HEI post above with the wide plug gap and burning the rotor?
Same thing, spark finding easy path to ground.
On the iridium plugs I have seen where the older IGN systems dont always like to play nice together.
Some have no issues and other do and no reason why that is so?
Me I will stick to the good old copper plugs the IGN system was made to work with.
Dave ----
So if the wires are a little weak they could leak spark to ground and cause a miss fire.
I have seen bad plug wires cause the spark to jump from the coil tower to the neg side of the coil.
Had it happen on my 02 Durango more than once till I told the dealer to change the plug wires.
Remember the HEI post above with the wide plug gap and burning the rotor?
Same thing, spark finding easy path to ground.
On the iridium plugs I have seen where the older IGN systems dont always like to play nice together.
Some have no issues and other do and no reason why that is so?
Me I will stick to the good old copper plugs the IGN system was made to work with.
Dave ----
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