383 Spark Plug Heat Range

[JGC403]

I have an old service manual that a J11Y plug should be used in a 1968 383 4 barrel. But by now the engine is far from stock, so It probably needs a different plug. Compression is about 10.0:1 (probably slightly lower after cleaning up the combustion chamber) Mopar solid lifter cam 284/284 duration, .528/.528 lift, tunnel ram intake with 2 x 4 barrels, ported "906" heads with MP templates, HEI ignition, headers, that is probably the major stuff. What plug heat range would be recommended for my combination?

 

[JGC403]

The pistons that are in the 383 have a large dome, with a spark plug relief. Will I need a non-projected plug or will a projected plug clear?

Anyone using Racing plugs in there big block?

I'm thinking of the NGK-2298 (this should be stock heat range) or NGK-2746 (should be 1 step cooler than stock)