In the Monte Carlo and Toyota I use OEM rated . Other than that I'm usually using autolite or AC . For right now as a " performance" plug I would probably use a platinum or dbl platinum autolite .
IMO there is no such thing, the E3's probably have the best reputation as maybe doing a little something over stock, but it's marginal at best I like Standard NGK's myself for reasons other than their performance
I would avoid precious metal plugs for performance use and keep them in long lasting OEM vehicles. They have been thought to contribute to detonation.
The NGK UR-5 is a very good plug for performance engines. It is one step colder than the stock plug. It is also a projected nose plug, so it has in theory, a wider heat range. It also places the gap deeper into the combustion chamber. http://www.rockauto.com/en/parts/ngk,2771,spark+plug,7212 http://www.rockauto.com/en/moreinfo.php?pk=33178&jsn=256 I use the flat seat equivalent (FR-5) in my aluminum head motor.
The R45TS plug has the smaller gap for the pre 74/5 engines with the points distributor. THe TSX has a bigger gap for the HEI motors.
TSX also has the extended tip to ever so slightly add compression. Puts the fire down in the hole a bit more. I've been running them for years.
In the snowmobile racing world we've done extensive dyno testings. including sparkplugs. All the trick plugs were no gain. E3's lost hp...we theories the big ground electrode covers the spark. Because we saw some gains on our stockers with projected nose plugs we got the factory engineers involved. What they told us is basically that puts the spark closer to the piston which advances the spark...so in reality some of our engines just needed a little more advance. One more note. projected nose plugs could cause detonation in higher compression engines.
Agreed, but much higher compression ratios, like race engines, they need race plugs with recessed center electrodes.
Since I run nitrous now and then I run the NGK YR 5. But the plug Larry mentioned the NGK UR 5 is a very good plug to use I was using that before I ran the nitrous.
I find the NGK UR5 are very good for these engines... Even on a worn out engine they resist fouling a little better than there types I find. Stock replacement plugs are good too....
