4.2 mini-stroker spark plug temperature?

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Thunderdonkey
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4.2 mini-stroker spark plug temperature?

Post by Thunderdonkey »

This should be my last damn question before getting this thing back in the vehicle (still plan on dropping the transmission/T-case in order to rebuild the latter, clean everything, and get the wiring harnesses installed neatly)...

My 4.2 mini-stroker is running a ~10.3:1 static compression ratio with a somewhat mild cam (slightly-modified Comp 68-201-4, if I'm not mistaken). Should I plan on running stock plugs, or something cooler? I'm guessing the former seeing as I can't find any discussion of the topic outside the scope of "normal" strokers (4.6+).

Thanks in advance.
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Re: 4.2 mini-stroker spark plug temperature?

Post by Russ Pottenger »

Whichever spark plug you choose just make sure you’re dropping down a couple heat ranges
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Re: 4.2 mini-stroker spark plug temperature?

Post by Thunderdonkey »

As always, thanks Russ! What’s the primary reason behind this? Compression ratio increase (dynamic or static), displacement increase, or something else?
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Re: 4.2 mini-stroker spark plug temperature?

Post by Cheromaniac »

The reason is basically to reduce the risk of detonation now that you're running higher static & dynamic compression ratios.
Stock plugs are Champion RC12LYC so you could use the colder RC10LYC.
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Re: 4.2 mini-stroker spark plug temperature?

Post by Thunderdonkey »

Thanks guys. I ended up grabbing some NGK BKR7E-11's and gapped them to .035". Once I've done the initial engine break-in, I'll pull them and check for fouling to see if I need to go hotter.
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