spark plugs

56yblock said:
what do you think the 11 RF 18 YC champion
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Those are two different plug heat ranges. Unfortunately modern manufacture Champion plugs rightly or wrongly do not have the reputation they once had. Autolite 45 or BF42 are well suited to these engines, and I've heard good things about NGK plugs.

In most cases the "normal" heat range plug will give good service in a stock engine, unless one is running extended highway use in the summer. Keep in mind a common tuning error is to install a hotter plug when the issue is actually incorrect ignition timing and/or carburetor tuning - jetting, power valve etc. Plug fouling for example. Modern fuels don't color the way leaded gasoline did, either on the plugs or exhaust. They can look somewhat lean and still running very rich. So it's a cut and try method. Make sure you have a good HOT spark ignition, timing curve squared away, and carburetor tuned well before deciding you need a different heat range.
 
I had the best results by asking the kid at O'Reilley's for spark plugs to fit a 1960 F100 with a 292, and buy NKG. In my 312, the NKG brand outlasted Champion, and performed better while doing it.
 
I have used 46's in my two Y's. That seems to be the recommended plug. Plugs always looked good with a nice tan color on the ceramic.
 
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I’ve run NKG’s in everything since at least the mid 70’s. They just seem to work and last. The only exception is my daily drivers with the 50,000 mile plugs. I live with the OEM’s on them.
 
I use the Autolite #46's in my '55 Customline with a 272. Car now has a quarter million miles plus on it with the last 90-100K miles being with the 46's. I try to change them out at 40-45K mile intervals and they always look good. The car has electronic ignition which explains the spark plug life. Ted Eaton.
 
The compression ratio is a big player when selecting the heat range for the spark plugs. The lower the compression ratio, then the need for a hotter spark plug. The 272 with 7½-8:1 compression ratio is happy with the 46 Autolites. As the cubic inches goes up, so does the compression ratio when all else is equal. For the 9-9½:1 292's, I'll use the Autolite 45 spark plugs. Ted Eaton.
 
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