Sparkplug gap?
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Elder User
Joined: Aug 2011
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From: Tucson, AZ
Sparkplug gap?
Hey guys, I have an HEI type distributor (GM, with the coil built in) in my 69-70 351W. I am finding different sources recommending different gaps on the spark plugs. Some say .035 others .045. Any idea which is correct?
Thanks,
Tyler
Thanks,
Tyler
Laughing Gas
Joined: Jun 2007
Posts: 815
Likes: 29
From: Richland, WA.
The HEI throws a hotter spark I think I would run the .045 to get a better spark. I use to up the gap on my sbc when I put in HEI. You could always run .035 and be safe. What motors can the HEI be used in? Will it work in a 292? I just found 3 of them in the garage and a recurve kit as well.
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Elder User
Joined: Aug 2011
Posts: 649
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From: Tucson, AZ
The HEI throws a hotter spark I think I would run the .045 to get a better spark. I use to up the gap on my sbc when I put in HEI. You could always run .035 and be safe. What motors can the HEI be used in? Will it work in a 292? I just found 3 of them in the garage and a recurve kit as well.
oldmerc
Joined: Jul 2011
Posts: 1,538
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From: Edmonton,Alberta
Hei distributers are available for many engines , check Speedway or Summit . Bubbas can probably convert for anything oddball , He quoted me $300 for a 239 flathead . When GM used the first generation coil in cap HEI the plug gap was .080 inch , giving you a nice big spark . I would try .060 and see how it runs .
Fleet Owner
Joined: Jul 2004
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From: NM
It doesn't improve anything to have a wider gap. GM used huge gaps to fire very lean mixtures on EGR-equipped cars. It was cheaper than designing efficient combustion chambers and port fuel injection.
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Elder User
Joined: Aug 2011
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From: Tucson, AZ
Hmmm...I'll have to check on that. Thanks!
T
T
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Laughing Gas
Joined: Jun 2007
Posts: 815
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From: Richland, WA.
I have seen electrical displays that had adjustable gaps on the electrodes and the wider the gap (within reason) the more intense the spark. Wouldn't the same theory apply? The DUI electronic dizzy says for flathead recommended gap is .055. Is that more than usual? I'm just curious.
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Fleet Owner
Joined: Jul 2004
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From: NM
What "DUI electronic dizzy"? I have the MSD Ready-to-Run distributor, it uses an HEI cap and rotor, but is not an HEI-output system unless you run the corresponding coil and wires and an MSD-6A controller. I've heard nothing but troubles with people running flatheads with gaps wider than .030 - .032, most recommend staying with stock .025 (unless you have a blower). Making a hotter spark takes energy from the coil and electronics, and if it isn't needed, it's just a waste. The original flathead coils were very low output, something like 15,000 volts. They worked fine as far as lighting off the charge.
Laughing Gas
Joined: Jun 2007
Posts: 815
Likes: 29
From: Richland, WA.
What "DUI electronic dizzy"? I have the MSD Ready-to-Run distributor, it uses an HEI cap and rotor, but is not an HEI-output system unless you run the corresponding coil and wires and an MSD-6A controller. I've heard nothing but troubles with people running flatheads with gaps wider than .030 - .032, most recommend staying with stock .025 (unless you have a blower). Making a hotter spark takes energy from the coil and electronics, and if it isn't needed, it's just a waste. The original flathead coils were very low output, something like 15,000 volts. They worked fine as far as lighting off the charge.
This looks like a HEI and I believe it has .055 gap HOWEVER I do not know the motor or what runs best as you do. I realize sometime what is advertised does not always work best.
Fleet Owner
Joined: Jul 2004
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From: NM
Note it says "allows you to open the gap to .055"...
I suspect the ad is the same for several engines. I will say it's good of them to (at least claim to) curve the distributors for each application; MSD shipped my distributor with a curve for SBC's.
I suspect the ad is the same for several engines. I will say it's good of them to (at least claim to) curve the distributors for each application; MSD shipped my distributor with a curve for SBC's.
Laughing Gas
Joined: Jun 2007
Posts: 815
Likes: 29
From: Richland, WA.
Well that better than nothing, I know there were times I was greatfull she started. I'd like an eternal coil HEI for the Y block but will go with electronic adapter.
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