[redmodelt]

You can use the 14MM adapters and your heat range of different plugs really increases. No plug hot or cold is going to stay clean if the engine is running rich or burning a lot of oil. Also running at the best advance for running condition with the distributor (or timer) helps. Cleaning your plugs is just part of the fun in owning these old cars. No matter what plugs you use, No 1 runs cold and No 4 runs hot so you have to find a balance.