What do these plugs say?

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AC sports
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What do these plugs say?

Post by AC sports »

At a glance what do these plugs tell you?
Afrs are 12-13:1 from idle to redline. Pump unleaded fuel.
Timing hotspot at the bend of the ground strap so seems ok. The slight sooty base thread is from momentary idle before shut off.
Btw. Twin carburettors on an inline 4.
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greenhj
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Re: What do these plugs say?

Post by greenhj »

Are all 4 plugs consistent in appearance?
AC sports
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Re: What do these plugs say?

Post by AC sports »

All consistent.
Afrs according to the meter perfect, but to me plugs look a little lean?
David Redszus
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Re: What do these plugs say?

Post by David Redszus »

Heat range and application? Ignition timing?

Cut the threads off and view the insulator center for heat ring.
They look hot to me. :)
AC sports
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Re: What do these plugs say?

Post by AC sports »

Max ig timing is 36*.
They are ngk 7's. May consider going to an 8 or taking out a couple of degrees timing.
Its predominately a fast road. Weekend short coarse hill climb car. 2v hemi head in line 4 making close to 100bhp/litre
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Re: What do these plugs say?

Post by ClassAct »

Look close and look for any little signs of detonation. I can’t see any but it’s just a picture. Those plugs look rich on pump gas to me. If you have more than 3 thread of heat in the shell the plug is too hot. How much compression are you running. BTW, the A/F meter can and will lie to you. If you are tuning to an AFR you may be using the mark.
AC sports
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Re: What do these plugs say?

Post by AC sports »

CR is 10.6:1
I've been hearing a little detonation lately coming onto the cam hence my concern.
The Afr meter says they are good but I feel they are a little lean. Pump gas here is 98 ron. From memory 93 u.s. octane.
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Re: What do these plugs say?

Post by David Redszus »

When an engine is operated at full load for an extended period of time, spark plug
temperatures will increase significantly. Therefore, a much colder heat range must
be specified for endurance racing, compared to drag racing.
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Re: What do these plugs say?

Post by rebelrouser »

for what my opinion is worth, they look good. Maybe slightly rich, but I never tried to run on the ragged edge, as I never class raced. The heat mark on the strap is not clear to me, as the plugs have some time on them, I get the best reading with just a few pulls on the dyno, or runs at the track. If I had a plug reading as pictured at the track, I would slow the timing a couple degrees make a run and see what the MPH did, if it got better try a set of colder plugs if it got worse, set it back where it was and run the engine.
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