The Motorcraft SP-447A plugs replaced old Motorcraft number AGSF32C. They're actually a 4 cylinder plug lol! That's weird. The Autolite number is 104.All will work if your ignition system is strong enough. I recommend .045 with autolite 3924s for naturally aspirated combos. I don't know your plugs but if they're right for the heads and copper core the gap should be the same.
I gap mine at .045. That’s what the gap is on SP-447A out of the box.I'm using Motorcraft SP-447A Plugs with the GT-40x heads. Was just wondering what you guys that are running these heads are gapping the plugs at?
When I bought the motor, Ford Racing said 0.044. I've seen 0.045, 0.050 and 0.052.
Thanks !
I still have the 2006 Ford Racing catalogue that had that engine in it lol! But there's no info on the pistons. Just that they are Hypereutectic. I don't know about flat tops. I think they only came on 1986. The Hypereutectic dished dome with four valve clearance reliefs came on the 1993 5.0's, and the 1993 Cobra Gt-40. That's according to the Mustang 5.0 technical reference hand book? I think I remember that the short block was a production 93. Makes sense. they probably had a bunch laying around to use up. They were used on the 94's and 95's too.I would say that the pistons are flat tops. The heads are the GT40X which have a 64cc combustion chamber, pistons probably have around 5cc of relief, head gaskets are probably around 0.040" thick compressed, and the pistons will be anywhere from 0.0075" below to 0.0135" above the deck so call it 0.00". All of that will give you right around 9:1 compression.
Ford's recommendation on that motor is 30 lb/hr injectors.
Motor data came from here:
Cylinder head data here:
Yeah, the 24's are right on the limit. 345 hp at 90% duty cycle. That's what the rated horse power is for the engine. I might just get some 30's at some point and a new Pro- M MAF meter for 30's and be done with it.Only thing that will tell you for sure is a wide band. I’m always going to over size the injectors as they can be tuned to work just fine. If they are too small well you just wasted money. Not saying the 24’s won’t work but 30’s provide more than enough.
Exactly, I read 30's are preferred. I've been running the 24's since 2007 lol!If you're N/A making 345 bhp, 24s should be running at ~90% duty cycle (assuming a very conservative .5 BSFC). So, as mentioned, you're fine. If you REALLY want to confirm it to yourself, you don't need a wideband. You can use a digital multimeter off of an injector and have a buddy read it while you're at WOT.
If you pay attention to the way Ford selects injectors, you'll find that in most applications, they put 1 lbs of injector for every 10hp they rated their cars. So, 30 lbs are probably "better", in that they'll keep the duty cycle down, but injectors either support the power or they don't. Yours do, or at least should, and therefore you'll end up wasting your money for nothing with this upgrade, now. If you go forced induction later, or install a tuner of some kind, 30s may be the wrong pick at that point. So, save the money, and get the right ones when you need em.
Before you go down some expensive rabbit hole, would you mind explaining why you think you need to swap them out? It seems like you read 30s are preferred and that's got you wanting to throw away money.
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