440 U-Code Spark Plugs & Wires

[RT70]

Unless you are circle track racing, have a power adder, or very high CR, there is no reason to use cold J11 plugs. After that era, spark plugs started using a copper centre electrode encased in a nickel/steel case that gave the plug a much wider heat range. Result was the centre electrode burned off the deposits from excess idling/low speed running that caused misfires/rough running. It also allowed hotter plugs to be used because the copper allowed for better heat dissipation than steel.
The correct plug is Champion 14 heat range, or 5 in NGK. Contrary to popular belief, you want the hottest plug that does not cause pre-ign....not the coldest plug.
Also a lot of nonsense written about the best plug wires & resistor plugs. In the test below a non-resistor plug came last & the leads with lowest resistance did NOT make the highest hp.

View attachment 1964245

Thanks, a lot of info, very good.

 

[RT70]

J11y is the better plug but haven't been manufactured in decades. I use autolite 85's as a substitute. OEM wires would have been 7mm carbon core; farly high resistance. J11y plugs were non- resistor, 85's are resistor. OEM wire plus the 85 plug will have more resistance than original. It may be debatable as to the pro's and con's to this but i try to stay under the service manuals 9000 ohms resistance per cylinder.

The local Oreilly's Auto Parts store does have "Autolite AP85" spark plugs, will these work?

 

[cosgig]

For wires, I have been using FireCore wires with good success. I have the 7mm 440 set on my 70 6bbl car. I also use the 340 7mm sets on my Cuda’s, and I have the 8mm set for my plow truck because it has MSD ignition and distributor.

 

[RT70]

For wires, I have been using FireCore wires with good success. I have the 7mm 440 set on my 70 6bbl car. I also use the 340 7mm sets on my Cuda’s, and I have the 8mm set for my plow truck because it has MSD ignition and distributor.

Thanks for the info.