What spark plug heat range?
05-20-2012, 02:16 PM
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What spark plug heat range?
I am currently running a 468ci w/ a MSD 6-M2, 800cfm carb. I have AC Delco CR43TS, curious as to a preferred heat range on plugs. Working on my timing and such and my plugs are pretty sooty... Carb is jetted 75p 85s 6.5pv Thanks!
05-20-2012, 03:15 PM
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It looks to me your plug heat range is about right. My suggestion is you lean out the mid RPM range by going to a PV that opens later...like a 5.0 or 4.5. Using a vacuum gauge is best vs. just guessing. Once on plane with your 6.5 PV's and a normal boat weight, see where your vacuum is every 300 RPM from 2500 to WOT. You shouldn't need the PV's to open until you are under significant load or about 75-80% max RPM. If you are still rich prior to the PV' s opening, start to jet down. With PV's and square jetting, I expect your jetting will in the low 70's. We target our setup so the AFR w/ PV's to be 14.0 - 14.5 AFR at cruise and a very safe 12.5 AFR at 80% to WOT.
