Spark plug rec for 454 with 9.5 comp and 049 heads.

[rally]

I used autolite #24 plugs on my old BB setup with 049 heads, 11-1 compression. Motor ran well with this plug.

[jdavis]

From testing with this engine, the projected tip plugs were better due to all the street miles and cruising. The actual problem with the plugs was not the ignition or carb at all, but the hei power wire was dropping voltage while running. The result was random multiple misfires or just horribly weak spark.

The ur4 is a fine plug just a little hotter than the 5. With a bbc check to make sure you have piston clearance with the projected tip if you do run them.