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Spark Plug Recommendations?
Which Plugs are you guys using for the 351C 2V, if they are different than the 4V version?

Is anyone usung newer Platinum or Iridium plugs?
I like plain autolite 25 or the colder 24 for a hot rod motor. I dont like platinum or iridium plugs, I think they are designed for computer controlled cars and leaving them in for one hundred thousand mile intervals, I prefer to check them or change them once a year or sooner to keep an eye on them, and see how rich or lean its running.

[Image: mustangnight010.jpg]
1972 Mustang Convertible 351C 4V
1966 Ford Galaxie 7 litre-4speed

I am running NGK Racing Spark Plugs in my 408. Those are the plugs that my engin builder installed and recommends. His recommendation is based on dyno experience trying various style plugs. I am also running an aftermarket ignition (ICE Ignition) which may be part of the rational for the plugs.


[Image: 57_23_07_10_12_47_19.jpeg]

White 1973 (351C stroked to 408, 4V, FMX) convertible with blue deluxe interior AC and power windows.

Irwin Pa (MCA # 52193)
+1 autolite 25 or 24.

you don't need any fancy plugs they don't increase horsepower, same with fancy ignition wires they are worthless junk. if you have weak ignition you have other problems before the spark gets to the wires or plugs.

spark plugs can be used to further tune an engine.

autolight 25s are normal, 24s are 1 heat range colder, 23s are 2 heat ranges colder, 26 is hotter.

the idea is you tune the heat range to what your engine is doing under normal conditions.
you want the engine in a certain heat range usually 170 to 190 degrees if the engine runs too cold it takes forever to warm up and you get crappy fuel economy and the engine can hesitate.
to hot and you over heat and bad things happen.

The way to check the heat range is first on your temp gauge next is by the plug, on the threaded part of the spark plug you want to see heat discoloration for about 2 threads if its too cold there will be no discoloration on the spark plug body, and too hot and the discoloration will travel up the plug much further.

you can also use a plug to get timing information and condition of the engine and if you need more fuel at WOT or you have too little at idle.

but autolites are good and cheap and do the job.
I bought Autolite 25s and installed them. Not to bad to change except for #2 and 8; tough getting around the Mstr Cyl and pwr string pump.

All my plugs that I took out were dark brown/rust color; what would that indicate?

Also, the timing shows at about 25 to the right of the "0".
Anyone know what this setting should be?

Thanks all!
Well you need to look at more then just the color to get an idea of what's going on.

Usually the darker the richer the engine is or you might be doing a lot of idleing.

You want to see how much of the puffy black soot is on the outer ring of the plug and down the isolator.

There are a lot of sites that show dark or rust colored plugs as normal, it can also depend on fuel additives. Bone white plugs are when the engine is running very lean.
There should be color to them but they should be uniform, you should be able to see a darker ring right around the electrode that helps figure out if your idle mixture is good and if your timing is good.

There should also be a discoloration of the plug Side electrode you want the discoloration right in the middle of the elbow, to have correct timing for the motor.

25 to the right of 0 would be 25 degrees of timing. If your getting this at idle it would mean your vacuum advance is kicking in, to find out your initial timing you would plug off the vacuum advance then take a reading with your timing light.

You could have any amount of initial timing that your motor and starter can take.
Too much timing can cause very hard starts or dieseling when shutting a motor down.

Every motor is different and reacts different to timing. Ford recommended initial at 6-8 degrees, some people like 10 degrees as a starting point. The more initial timing the motor has the more power you make at the cost of drivability.

When playing with timing and spark plugs you first have to get the heat range right, motors can tolerate a huge range, but to start getting a sweet spot for a tune you have to get the plug that makes the engine run at the right temperature. Once you find a plug that shows discoloration on the threaded base of 2 threads then, you put 50 miles on it and pull the
Plugs for a look, you see the location of discoloration on the Side electrode and from that you can tell if you have too much or too little timing.

Then you drive some more and pull them and look at how carbon fouled they are.

It's easier said then down, but it helps get you in the ball park of what your engine wants. What works for one guy will not work for you.

I've been playing with it for a few years and I'm still learning.

My last plug change I went too cold on the plugs so I have some issues when the engine is cold.
I use Champion 3025's in my early '71 stock 351C 4V with good results.


Which Plugs are you guys using for the 351C 2V, if they are different than the 4V version?

Is anyone usung newer Platinum or Iridium plugs?

[Image: 1_11_11_13_11_50_27.png]
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