I have a 1984 f-150 4x4 with a freshly rebuilt 302 HO from a 83 mustang in it. All new stuff inside. My question is about the plugs. An ole mechanic tells me to go one number colder than the plugs that the auto parts people recommend. I would feel the difference in performance. Also should I buy plugs for the 84 302 or the 83 HO with performance parts inside or does it make any difference? I am thinking about autolite platium??????

Thanks for your comments
JJH

 

Platinum plugs will do no better than regular plugs would. The general rule is that if the car originally came with platinum plugs, then you should use platinum, otherwise they won't make a hill of bean's difference except cost 5 x more. In fact, some platinum plugs will delaminate from the insulator core when subjected to a high-Voltage ignition system, such as an MSD. Run Motorcraft plugs, they're every bit as good as the others. Spark plugs will only make super-marginal differences in power anyway, so don't waste your time and money grasping for 1/2 horsepower @ 7,000 RPM. It will be nice though to upgrade the ignition so that you can open the gap up. The heat range is critical to preventing preignition, which becomes an issue as compression increases. Colder plugs will not clean themselves as quickly, but they will be safer from causing engine-destroying detonation. It's best to run the hottest heat range that will not preignite the fuel, this keeps combustion chamber deposits under controll, and emissions low. TK

'77 F100, 302 (the aftermarket Prodigy), C4
Cadet Second Lieutenant John F. Daly III
South Carolina Corps of Cadets, The Citadel
The TorqueKing

 

Ok so the platium plugs might not be a good idea, but. Now the issue of the colder plugs. My heads have been shaved 25,ooo which has increased the compression. Right? So colder or not? Good Idea! Bad Idea! Don't Really Matter?

Thanks JJH

 

If your heads are shaved, then go colder, just to be safe, it won't really hurt. The next heat range down will still be plenty hot to keep your deposits at bay. TK

'77 F100, 302 (the aftermarket Prodigy), C4
Cadet Second Lieutenant John F. Daly III
South Carolina Corps of Cadets, The Citadel
The TorqueKing

 

Hey Thanks TK! One other question which I should have already asked is, if I won't a plug that is one heat range lower would the number of the plug be higher or lower. Reason I ask is the guy on the phone at advance tells me that the no. would be lower but a different salesmen another day tells me it would be higher???? What you think?

thanks JJH

 

[updated:LAST EDITED ON 14-Sep-02 AT 09:11 AM (EST)]It depends on the brand. For instance, AC Delco plugs have a part # such as "R45TS". The number indicates the heat range. For most other spark plugs, to include Motorcraft, 1 number lower is one heat range colder. AC Delco spark plugs go the opposite way. Some parts stores go by the stock number. A common spark plug for Fords is the Motorcraft 450, this is a stock number, not a real part number, so you can't tell the heat range from this number. However, there will be the real part number stamped on the box, such as "AS44TS". Here, the number 44 is the heat range. If this were the correct spark plug for your application, ask for a set of "AS43TS" plugs, those are the heat range you need. Also, make sure you are buying from a parts counterman that knows what he's doing. Check the gap, and reset it to OEM specs if not already set. TK


'77 F100, 302 (the aftermarket Prodigy), C4
Cadet Second Lieutenant John F. Daly III
South Carolina Corps of Cadets, The Citadel
The TorqueKing