FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: BigBlueIron on March 25, 2022, 09:45:40 AM
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A friend just gave me some NOS Motorcraft BRF31 spark plugs, about 30 of them.
I plan to run them in a fresh 390 with about 9 to 9.5-1 compression. Duraspark distributor hooked to an MSD digital 6 plus. Any flaws in this plan? anyone familiar with these old plugs? What little info I could find seems like these should work really well for the application.
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I am unable to find a good Motorcraft part number breakdown listing but here is the best I can remember.....Just be warned the only thing I can remember is that I don't remember.
B= 18mm thread diamerer (either cone seat or gasket seat)
R= is either "resistance style" or the depth of the electrodes
F= cone seat.
31 = heat range...on the cold side.
I believe this plug crosses to the Autolite 124 so it should physically fit in the standard FE head.
But be certain the threads and electrodes are not too long, or short.
If they look to fit, run them and check the heat annealing ring to be sure they are the right heat range for your needs.
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I ran BRF32's for years with old TRW pop ups in a 390 4 speed mustang. To this day it was the most fun in a street car I ever had. Hand ported iron heads, FPP rockers, a PAW cam, offenhauser 360*, 700cfm dbl pump Holley, Mallory YL dual point, top loader, 3.70 limited slip, slapper bars, crager sst, ... Dam I miss that car.
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I am unable to find a good Motorcraft part number breakdown listing but here is the best I can remember.....Just be warned the only thing I can remember is that I don't remember.
B= 18mm thread diamerer (either cone seat or gasket seat)
R= is either "resistance style" or the depth of the electrodes
F= cone seat.
31 = heat range...on the cold side.
I believe this plug crosses to the Autolite 124 so it should physically fit in the standard FE head.
But be certain the threads and electrodes are not too long, or short.
If they look to fit, run them and check the heat annealing ring to be sure they are the right heat range for your needs.
I was leaning towards running the 124's before these fell in my lap. The electrode depth/stickout whatever its called looks identical to a 124.
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'Back in the day', my '64 Custom/427 wanted BF 32s. That's what came in it from the factory, and that's what I used for replacement. BF 22s worked fine at the digs, but quickly fouled in street driving. BTF 1s were showing signs of fouling after about three runs at Detroit or Milan.
KS
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I gotta say, that I had never seen a BRF31 spark plug, I have ran Motorcraft for years, BF42,32,22, and even BF12 (very cold). I always thought that , at least on the 18mm plugs for FEs, that a BF32 was one step colder than a BF42, a BF22 was one step colder than a BF 32, etc. Like Ken said, the BF22, (and the BF12 was even worse), would foul up quickly, at least with the old dual point ignition we were running years ago. Back then, I had a set of BF42 "Warm up" plugs that I would run the car on in the morning at the dragstrip, until it got up to temperature, and then put in the colder plugs for the drag strip runs. My 66 Fairlane 390 GTA had manual steering and brakes, with the single bowl master cylinder, so I could change all the plugs in about 15 minutes.