Spark Plug suggestions

[matt1190]

Well, this is pretty general,...but I'm curious because I want to change my spark plugs and would like to know what everyone recommends for their own mustang. Currently I'm running bosch platinum 4's and ever since I possesed the car, I've not had the chance to experience the difference of any other spark plugs. (It's a daily driver, 351w, stays really cool, 9:1 compression.)

[Jeff65]

Take your plugs out and look at your existing plug tips. The tips will tell you how well they're working.

a. If black and dry, they are too cold for your driving habits. Get a hotter plug from your parts store.

b. If black and wet then: wet with oil, need engine overhaul, wet with gas, need tune up or carb work.

c. If very white flaking or rosy insulators, look for destruction of insulator tips, plug is too hot or incorrect fuel octane.

d. Should be light grey insulator tips, fading to white, no evidence of electrode wear, no misfires. In this case you have the right plugs installed.

[matt1190]

Thanks Jeff, but what do you run in yours or what would you recommend? Currently my plugs are dry and DARK browninsh gray,..I'm happy with the carb settings even if it is a little too rich, so I'm wondering if I need a hotter plug to better burn the fuel. I've heard a lot of people tell me NGK plugs kick ***, and I've heard the same of Autolite. What do you guys think? I'm running a Fireball ignition box by comp cams with 8mm wires off of a motorsport vac advance distributor, if that helps any. THanks!

[Jeff65]

Originally posted by matt1190
Thanks Jeff, but what do you run in yours or what would you recommend? Currently my plugs are dry and DARK browninsh gray,..I'm happy with the carb settings even if it is a little too rich, so I'm wondering if I need a hotter plug to better burn the fuel. I've heard a lot of people tell me NGK plugs kick ***, and I've heard the same of Autolite. What do you guys think? I'm running a Fireball ignition box by comp cams with 8mm wires off of a motorsport vac advance distributor, if that helps any. THanks!

You have a very hot ignition system and it will surely fire colder plugs. I would back off one heat range at a time until you get a lighter looking insulator after 10K miles use. Fact is your ignition system will kick *** with almost any plug that bolts in. You can use whatever you want to try, just look at the length of the center insulator. It should be shorter from base to electrode tip than the ones you're using now. Each shorter center insulator will be a step cooler. Hot plugs=long center insulator Cold plugs=short center insulator. Since you have hot ignition box you need cold plugs.

[66StangGuy]

iv tried the plats too but i didnt really like them much. i didnt really notice any problems but the car seemed to run a little different. its hard to explain. anyway i put in the autolite resistors with the stock heat range and it starts great and runs like a beast. i have not tried the nkg's but i give a thumbs up for the autolites.

[matt1190]

Well, I went out and bought a set of autolites #24 for my 351w. However, when I took out my old plugs I noticed that they had different thread lengths and what not. They don't look very correct to me, I've posted a pic of the two. I do have Trick Flow alluminum heads, but I wouldn't think that would mean that they would be any different than stock plugs. I drew a couple lines to show how long the threaded sections are.

The plug on the left is a Bosch (with the numbers 4417, R3 966)
The right one is an Autolite (#24)

I have been running the engine w/o any problems with the Boschs since 99 so which one is wrong? Any help would be appretiated!!

[hobgoblin351]

If that Bosche plug screws all the way in, it looks like the autolite is a wrong plug. Looks like it will never reach the combustion chamber. People make mistakes. It's possible they gave you the wrong plug, or that the trick heads dont use the stock plug.
I'm running a Cleveland, and anyone who has changed plugs on one knows IT SUXX! I usually run Platinum plugs just so I dont have to change them too often. Right now I've got a set of splitfires in there. They seem ok, no big difference. Like he said with a highfire ignition any plug will perform. Heat range tweaks are always good to ensure a good and total burn. Hell you can even set the electrode so that the gap faces into the chamber if you want to go crazy! lol

[Metal396]

i dont know anything about spark plugs except that i need new ones. i have a 73 mustang with 2v heads.... what spark plugs should i get taht will work well and last a long time? I wanna do the plugs now, and in a month or two i will install a msd billet distributor and an msd 6a ignition module, and probably whatever msd coil goes best with that setup.

It ought to be at least a little bit easier to do spark plugs on a 73 mustang, with a cleveland , because theres alot more engine bay space than a 70 . But i know absolutely nothing about gapping the plugs and the tools i need to put em in... thanks for your help.

[matt1190]

Well, I did figure this mess out. Turns out my alluminum heads have a thicker wall than a stock set would which would require a spark plug with more threads. I was finally able to get the specs on which plugs I could use through the Trick Flow tech guys. Thanks for your input!

Well, Metal as far as platinum plugs go, you could use Autolite's APP25, or NGK's UR4VX, or Bosch+4 (couldn't find a part #). Like other people have mentioned before, longevity and efficiency is what platinum is made for, wouldn't count too much on performance changes. If you're using a pretty stock ignition system I'd go with a .035 gap. Just buy a plug gapper, which looks like a Silver dollar, from the parts store so you can measure the distance between the center electrode and the wire electrode. Once you upgrade your ignition system, reset the gap to .045. Good luck. -matt

[Rev]

I didn't see a mention of the TFTW al. heads until the 3 rd post or so. Definitely a longer plug for the al. heads. My TrickFlow instructions mentioned recommended plugs. Did you not see that?

Rev

[matt1190]

The car was passed down to me, didn't have any of the paperwork for the heads which is why i wasn't sure about the plug differences,

[Rev]

Sorry fo my misinterpretation. TrickFlow will give you their reccomendations.

Rev

[Metal396]

Well i bought a pack of Motorcraft ASF42C spark plugs. The guy workin the counter said theyre plenty good for what i have done and plan on doin to my car... he said i wouldnt need anything fancy unless i had a built bottom end... forged pistons etc.

Should they be fine? I gotta borrow a gap-tool and spark plug socket from my friend and deal with that stuff.... Just thought id let ya all know..