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.

 

[coloradodave]

Don't be cheap about the spark plug wires - firecore spark plug wires, there is nothing better. None.

As for plugs many are stuck mentally in the 70's just like with operating temps, alignment specs and shocks. Today's fuel requires 195 F so get over it
From too many years of experience i find J11's are too cold. I run j14's in my current playtoy which gets run very hard and put away wet.

Thank you for your opinion on sparkplug wires...Do you have any advice for those of us mentally stuck in the 50s and 60s?