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1948 - 1956 F1, F100 & Larger F-Series Trucks Discuss the Fat Fendered and Classic Ford Trucks

Plug gap y block

Old Dec 11, 2025 | 10:15 AM
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Plug gap y block

What’s the performance difference between plugs on a 292 set at .032 or .040? I currently have them set at .034, starts and runs good.
 
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Old Dec 11, 2025 | 10:36 AM
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Originally Posted by wellcraft17
What’s the performance difference between plugs on a 292 set at .032 or .040? I currently have them set at .034, starts and runs good.
I always thought older vehicles ran closer gap due to limited secondary voltage (25,000 volts) compared to newer with electronic ignition. I'd say if you are running a hot ignition (40,000 volts) then .040 would be better
 

Last edited by bigwin56f100; Dec 11, 2025 at 10:37 AM.
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Old Dec 11, 2025 | 10:41 AM
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Originally Posted by wellcraft17

What’s the performance difference between plugs on a 292 set at .032 or .040? I currently have them set at .034, starts and runs good.
What the poster said - .034 -.035 with STD IGN.
 
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Old Dec 11, 2025 | 10:44 AM
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I wouldn't get too caught up on the gap as long as you are within the specified range and are satisfied with how things are running. The 0.34 is spot on according to Van Pelt:

Ford Tuneup Specifications for 1954-59 V8 Engines

Usually the gaps are specified as a range, and traditional wisdom says to try to aim for the smaller side of things as the gap will naturally grow with wear. It is also said that leaning towards the larger gap can lead to better fuel efficiency. A wider gap also can retard ignition timing. I'm sure there is a whole science to this all, but again, I wouldn't get all caught up in it all unless you are racing or similar.
 
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Old Dec 11, 2025 | 11:42 AM
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I have a pertronix ignition so I guess I’ll leave it alone.
 
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Old Dec 11, 2025 | 05:59 PM
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Originally Posted by wellcraft17

I have a pertronix ignition so I guess I’ll leave it alone.
IGNITOR I or II?
 
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Old Dec 12, 2025 | 03:01 PM
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Number one since 1992
 
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Old Dec 12, 2025 | 03:38 PM
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If it ain't broke, don't fix it is always a good rule to follow. The neat thing about plug gap is you can play with it and see what happens with no consequences. It either works better or it doesn't, and you can always put it back if you don't like the results in about 15 minutes.
 
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Old Dec 12, 2025 | 06:42 PM
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Originally Posted by wellcraft17
Number one since 1992
With the IGN II and III, you will be running hotter coil(s) and can increase gap (hotter/longer spark) as was done with DURASPARK allowing running a fatter fuel curve and a colder plug.

The FYB ran MOTORCRAFT BF-82 which is a hot plug.
 
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