What would you buy? It's basically a stock rebuild, nothing fancy, done 5-7k miles ago.

$2 Autolight? NGK? What do you guys run? I just pulled them because I'm doing a compression check, and it made me think....

 

So... Autolite 25s it is?

 

Unless you have a very special application going, the factory stock plugs are gonna be your best bet. The vast majority of these fancy, super duper spark plugs are just exactly that, all flash for a lot of money and no improvement in anything over you basic $2 spark plug.

 

Oh, I know that for sure, I'm not going to run out and throw some Bosch Platinum +4s or anything in

But alot of people have a brand preference, and for a good 'ol American V8 I thought I might get some people chiming in with plug XXX thats hotter or colder is better because the factory plugs were best for emissions, blah blah... stuff like that.

Same goes for gap. I know people pick different plugs and gaps than the factory recomended, but I don't know what or why

Try asking "what spark plug should I use" in a Motorcycle or Jet Ski forum and you'll end up starting a raging debate

 

I did learn one plug trick bad in the late 60's. The Ford FE truck engines ran the Champion RF9 or RF10 plugs while the cars ran the RF9Y and RF11Y. The "Y" plugs had an extend reach on the electrodes. Putting the "Y" plugs in the trucks boosted the mpg by at least 1 number and sometimes more. I have never checked to see if the car 460 ran a different plug than the truck but it might be worth the try.

 

See, thats the kind of stuff I'm talking about

I've got Autolite 25s in there now. They're not too bad, I gave them a cleaning and put them back in. They are the OEM plug I found. I forgot, I had them replaced just prior to the engine rebulild, so they only have 1k more miles than the motor

 

i've ran autolites, and a few others on carb and efi 460 engines. never noticed any big difference in any of them. i still run autolites though. if it was good from the factory and there hasn't been a recall it must work just fine for what it was made for.

 

Well, that and you could pretty much stick a chunk of coat hanger through some JB weld and it'd probably run the engine fine

I've spend so much time in the small engine world lately (you know, less than 7 liters lol) and there are so many pros-cons to different plugs on things like my JS550 that I was hoping I might have a choice here

 

set the gap for your spark and time it right and your golden

 

I just re-checked gap. I was pretty much spot on on all 8...

I do plan to check timing. I'm trying to chase a bad gas mileage problem. I'm getting like 3-4mpg lately, with seemingly nothing wrong yet...

 

i had an old farm/heavy equipment shop(holland and sons, no longer around) set up my carb and timing. no where near stock. after a couple of older mech tinkerer's set it up i got about 11 mpg's and a very noticable improvement in power, in an 85 f1504x4 with a c-6, 4.11 gears and 36"s. i was getting about 7-8 before that if i was easy on it, but you're in cali. so unless it's a trailer rig you've got smog f.ing you over. i did go from a holley that was worked over, to a 750 edelbrock performer manual choke/secondaries.

 

Well, a 460, especially a carbed 460 is never gonna be a mileage getter. My 1984 F250 Supercab, Superduty, 460, C6 and 4.10 rear end with stock tires, stock got 6 to 7.5 mpg depending on what I was doing (camper, boat, quad in the truck bed and little trailer with second quad or the dual axle flat bed with 4 to 6 quads or any combo of the former). I replaced the carb with a Holley 1850 that I had massaged (originally built it as a back up carb for my 1968 F250 with a worked over 390), recurved the dist. and installed a 3" single exhaust and I now average not quite 10 mpg. But the 4.10 rear end requires that I stay under 58 mph or the mileage gets back into the 6 to 7.5 range again.

 

Index your plugs towards your intake valve as close as you can. If you feel like experimenting, get a few sets hotter, cooler or different brands that are the OEM replacement. I used to work with a guy who swore by Autolites. I am not set on any particular brand myself though.

It all depends on how you 'tune' your engine

The gaps can vary between applications. Its generally the largest gap possible without causing a miss. Too large a gap will cause a high resistance; same thing will happen with in-cylinder pressures and turbulence. The higher both of those are the more difficult the ignition of the fuel will be. Too small of a gap will also cause a miss because of the less volume of air/fuel exposed to the flame kernal produced by the electricity jumping the gap.

Make sure you have electrodes that are square, not rounded etc.

Like Fatdan460 mentioned, just make sure you have the basics set and your engine should be great. Make sure your connections on everything are the best possible.

 

Two things about indexing plug. First unless you are looking to pull that last little single horsepower out of the motor, don't bother. Second and most important, with tapered seat plugs it is next to impossible to do it without either leaving the plugs too loose or way over tightening them. Neither situation is a good one.

 

I had my carb rebuilt and tuned by a local shop. He's got it running great, passed emissions, etc. But it's just the bad gas mileage. I'm trying to nail down every little possible cause before I ask them to work on it *again*...

Oh, I don't expect miracles. My concern for mpg is just that I used to get much better mileage before the motor swap. That tells me that somewhere, something is wrong. I'm finding all sorts of little things as I go, and I bet more than a few add up in the mpg department...

Yeah, I think this stemmed from my recent time spent working on my old motorcycle and 2 stroke Jet Ski. For either one, everyone tells you to run this plug or that plug, with a specific reason, and you get some good intel. I just wondered if everyone was going to tell me "well, for emissions Ford switched to xx plug in the late '70s, if you get plug YY from a 76' blah blah..."

Something like that. But if the stock plug is what everyone else runs, it's good enough for me (and what I have already)

Yeah, I'd never really give it any thought on this thing. I've got hundereds of pounds of torque, a few extra isn't worth the hassle. Although I did see "spark plug indexing washers" listed recently on some big website, CSK maybe. So you don't have to leave them loose

Thanks guys, I cleaned up my Autolite 25s, gapped them, and put them back in. I did decide I need new plug wires.... one of them was so badly corroded in the boot that it wasn't re-usable...