I have R45's in my 283 LCF, I think those are the spec heat range. Factory probably figured a farm truck would have a lot of low rpm and idle hours, I've had them in for 5 - 6 years and run it at 3500 - 4000 rpm on the road, no pre-ignition, no melted tips, I run a 180 degree t-stat. Stock ignition/distributor with governor.

Last edited by 78buckshot; 12/01/2023 2:15 AM.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy