Spark Plug Gap (1 Viewer)

[Trollhole]

Standard on a f and 2f are .031-.032 correct. I'm assuming this is about as far as you could gap the plugs with the stock coil. So if you used a hotter coil could you increase that gap and by how much? Would a hotter coil cause issues with the dist?

On another not I'm going to be running a 87 2f with stock a stock dist. But the coil will be for a chevy TBI system. I'm thinking of running a bigger coil. So I'm assuming I can run a bigger gap. How does one know how big you can go?

 

[brian]

HEI, ngk plugs, '77-ish 2f. i'm running between .060-.065 gaps.

 

[D'Animal]

FSM for a 2F in an FJ60 is .031".

I set mine at .035" with the stock electronic ignition set up.

 

[grant5127]

IIRC average chevy gap .045...... The gap adjustment can be fairly critical, and if it is maladjusted the engine may run badly, or not at all. A narrow gap may give too small and weak a spark to effectively ignite the fuel-air mixture, while a gap which is too wide might prevent a spark from firing at all. Either way, a spark which only intermittently fails to ignite the fuel-air mixture may not be noticeable directly, but will show up as a reduction in the engine's power and fuel efficiency. The main issues about spark plug gaps are:

narrow-gap risk: spark might be too weak/small to ignite fuel;
narrow-gap benefit: plug always fires on each cycle;
wide-gap risk: plug might not fire, or miss at high speeds;
wide-gap benefit: spark is strong for a clean burn.
A properly gapped plug will be wide enough to burn hot, but not so wide that it skips or misses at high speeds, causing that cylinder to drag, or the engine to begin to rattle.

 

[Degnol]

Does a wider gap tax the coil more?
Legit question as I have read other threads that say too wide a gap is not only unnecessary but will burn out coils more quickly.
I defer to Grant on this one.....


Ed



i have a plan for getting us out of iraq...:
They keep talking about drafting a constitution for Iraq. Why don't we just give them ours? It was written by a lot of really smart guys, it has worked for over 200 years, and we're not using it anymore.

This still knocks me out

 

[Pin_Head]

Does a wider gap tax the coil more?
Legit question as I have read other threads that say too wide a gap is not only unnecessary but will burn out coils more quickly.

Definitely. The wider the gap the higher the voltage needed to make a spark, especially under high load conditions. If the voltage is too high, the insulation will break down somewhere: the coil, distributor cap or plug wires. If there was any benefit to wide gaps and higher voltages than necessary, then all the manufacturers would do it. As long as it makes a spark, the fuel combustion and power is all the same.

The gap listed for F engines is .031 and the one for 2Fs is .039. Most gap specs I have seen are .035 and I haven't seen one larger than .045.

 

[Degnol]

Definitely. The wider the gap the higher the voltage needed to make a spark, especially under high load conditions. If the voltage is too high, the insulation will break down somewhere: the coil, distributor cap or plug wires. If there was any benefit to wide gaps and higher voltages than necessary, then all the manufacturers would do it. As long as it makes a spark, the fuel combustion and power is all the same.

The gap listed for F engines is .031 and the one for 2Fs is .039. Most gap specs I have seen are .035 and I haven't seen one larger than .045.

That was your post I recalled, glad you chimed in

Ed

 

[grant5127]

There are many GM plug applications that are gaped out @ .060 to .080........ very common through the mid 70s to early 90s.......

 

[Fuzzy Logic]

There are many GM plug applications that are gaped out @ .060 to .080........ very common through the mid 70s to early 90s.......

Very true! I have a Cutlass and the gap setting is .080 Totally blew me away

 

[grant5127]

Good God Gurdy What a Gash!

Very true! I have a Cutlass and the gap setting is .080 Totally blew me away

No s***? Imagine that.......

 

[JohnnyC]

Standard on a f and 2f are .031-.032 correct. I'm assuming this is about as far as you could gap the plugs with the stock coil. So if you used a hotter coil could you increase that gap and by how much? Would a hotter coil cause issues with the dist?

On another not I'm going to be running a 87 2f with stock a stock dist. But the coil will be for a chevy TBI system. I'm thinking of running a bigger coil. So I'm assuming I can run a bigger gap. How does one know how big you can go?

While in school we were told you can run up to 20% increase in gap size with no adverse affects of the ignition system...if you have an F engine with .031-.032 gap you should be able to go up to .038 with no issues....

as Pin_Head pointed out the 2F went to .039....thats just over a 20% increase...I would think since the 2F uses an electronic ignition system you should increase 20% from there to a gap of .047

If you run a hotter coil and electronic ignition system...good wires...i would say increasing that 20% should not be an issue.

with points ...i kinda think a large increase will affect the points life...never tried it though

when i was working on english racers we increaded the gap just under the 20% whenever we installed an Allison electrionic system and put a jacobs coil on...why we didnt goto exactly 20% IDK ...our boss was wierd

I may try increasing my gap to .038 and see how it performs.

 

[bsevans]

I have a DUI HEI and run NGK Irridium plugs. They come with a .044" gap. I believe DUI reccommends a maximum of .055". I think the standard coil on their HEI has a 50,000v output. I know when I was looking for a plug issue and checked each plug while the vehicle was at idle that when I found the cause the coil dischage had one hell of a greeting.

 

[Trollhole]

Found this. Pretty cool idea.

How To drill and index your spark plugs for better performance/economy. | eHow.com

 

[Coolerman]

Try it and lets us know the decrease in your 1/4 mile times...

 

[Fast Eddy]

Found this. Pretty cool idea.

How To drill and index your spark plugs for better performance/economy. | eHow.com

Call me skeptical. The explanation of #5, especially is hokey. By the time the plug fires the entire chamber is equally filled with high-pressure mixture. It certainly does not matter which way the electrode is facing.

The spark is a straight arc, no matter the shape of the electrodes. Their description of the "spark pattern" has no scientific basis.

 

[Trollhole]

I thought it was a crazy idea but hey look at what I just built. My luck one of the little pieces would come off and screw the pooch.