I have read post after post about different plugs. Right now I am running ACFR3LS in my AFR 190's. I am thinking of going to a Champion plug, but I am confused on the part numbers. I have see both RC12YC and RS12YC as the part #. Which is it? I know that the RC12YC has a washer and the RS version doesnt. The RC version has a 0.750 reach and the RS has a 0.708 reach. Im running around 10.5 to 1 compression on a L98 shortblock. Comp xe282hr cam, rpm airgap intake and holley 750 street hp. MSD 6A with MSD probillit dist at 40* timing. The car is street/strip and I run 93 octane on the street and a 93/110 mix at the track. The Ac FR3LS are a light tan but I cant read the mark on the strap. I think it is close on the heat range. Which plug is the right plug. Thanks

no help for just one small question?????????

I actually use a set of those older AFR190 heads on my Malibu. The plug is a .750" thread with a gasketed seat and 5/8" hex head. Autolite 3924s are what I usually use (although I use something completely different in my blower motor). So whatever would x-reference to that part number from Champion.

Thanks for the reply. I found out it is the RC12YC with the washer that I need. I think ac delco changed there FR3LS part number to a 41-xxx number.

I think I will try a set of the Champions. Most of the local part stores carry them for $1.79 each and Summit Racing wants $2.95 each.

You get what you pay for here. I wouldn't run anything but NGK in a good stout small block with AFR 190 heads (these latter became the AFR195). The ported and polished combustion chamber re-shaped 190 heads that I currently use have NGK-2687. 500+ dyno certified HP. These motors idle much better and provide a nice clean spark kernel well over 9000 rpm. I also had to switch to NGK Iridium for my 540 CID Marine Rats. 617 HP. Brodex - 2 heads in those. Same kind of work to the heads. Nothing that I have tried stay clean through long idle in and out of port. Very pricey and worth every penny of it. your very best bet is to call NGK. They will ask you questions about your build and come up with a plug. They have been helping our teams for years.

I wouldn't put champion in anything but a lawnmower or something that runs like a lawnmower, like a mopar...
If its a street car run the GM FR3LS to FR5LS or NGK.. maybe even autolite if nothn else around..
My cuz worked 4 champion in the R&D department not many good stories there.. lol

I run Autolite 3923 with my Trickflows. They ran alot smoother than a new set of NGK.

Those are also good plugs. The Iridium NGK's are a fine center electrode design. You really can't compare them to anything but a premium precious metal plug to be fair. I can tell you however, nothing we have tried runs like the Iridium NGK line. Very nice plugs. They are very difficult to foul. In some instances on very high compression competition motors we have built, nothing else would work well after extended idling. The very fine wire center Iridium plug will impress you. We have actually seen several HP gains with some combinations on the dyno's. I understand the complaints about Champion. There was a time (a long time ago) when they were the best. We had several failure to spark instances with Champion's in the past. We don't use them anymore. You can waste some serious dyno time chasing a brand new plug that is defective.

So far the Champions are working just fine. Im not saying they are the best on the market, but for the price they seem to work as good as the AC FR3LS.

I'd call NGK tech 1.877.473.6767... Think a BKR7E in NGK would be good.

I take it back. The NGK's made more vacuum when I was data logging.