[64speed]

I am using the NGK 4554. What is the next down colder plug?

[misterp266]

Here’s an NGK chart. You’ll need the long number. The example is a BP6ES-11. Hope it helps.

[steve25]

How did you determine you need a colder plug?

[64speed]

My buddy that races a 69 Lemans said it was worth a try after looking at mine.

[steve25]

A Worth a try comment to me sounds like your having issues, is that the case?

Keep in mind that just eye balling at a plug from a motor with street miles on it tells nothing unless your at the extreme’s of the plugs heat range in your motor now.

[64speed]

I was trying to determine if it’s detonating. You’re right the plugs revealed nothing cause it’s not ran at WOT all the time

[Jay S]

If it is detonating you should fine small aluminum freckles on the porcelain of the electrode.

That NGK plug you list is already a pretty cold plug. Going colder than that won’t gain anything.

[Jay S]

Originally Posted by Jay S

If it is detonating you should fine small aluminum freckles on the porcelain of the electrode.

That NGK plug you list is already a pretty cold plug. Going colder than that won’t gain anything.

That top line should say find, not fine. Sorry about that.

[HWYSTR455]

You should post pics of your plugs and see what others think.

Did you get the carb and timing dialed in?


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[Formulas]

If a colder plug helps you out and doesn't foul ... good on ya .. This group does not allow such operations

[HWYSTR455]

I would agree with that possibly if I actually saw a plug, but not going to go off heresy.

If the tune is off the heat range ain't gonna tell you jack.


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[NeighborsComplaint]

Hard to hear detonation over the loud exhaust and roller rockers. Plugs would look gray with aluminum specs on the porcelain like others have said. If you borrow or buy a borescope, you will see pitting on the piston tops instead of carbon buildup.

When you lug the motor down in overdrive on a slight incline, you should be able to hear it ping over the exhaust at light throttle. Does it diesel when shut off?

[JSchmitz]

As already stated, look at plugs for aluminum specks on the porcelain. Look with a magnifying glass. A friend of mine was talking about how his engine ran fine on 87 octane. I suggested looking at a plug. It was coated with AL.

[steve25]

If your detonating with aluminum heads they do show more aluminum transfer to the plugs since your blasting material off both the Pistons and heads .

however if you find a lot of aluminum transfer with iron heads then your Pistons should look like Hell and your rod bearings on the cylinders that are detonating are likely well on there way out depending on the rpm the motor was being run to while detonating and you may have busted some rings if the motor is using oil.
And if it is using oil then the exasperates the detonation condition .

[Kenth]

Lugging the engine in overdrive at low speeds will make any engine ping.
Changing plugs is no remedy, shifting gears is.

[grivera]

What is your compression?

[64speed]

10.25 is compression. I don’t lug the engine.

[Kenth]

Too fast centrifugal ignition advance?
Too lean carburetor?
Too rich carburetor?