[mikey]

Having suffered a backfire through one cylinder I found one of my plugs was not detonating properly. Further investigation revealed a second plug misbehaving.

A bit unusual as the plugs have done very little mileage - NGK BCPR7ES. The engine is well tuned so the heat range at 7 should be about right. Doing a bit of a web trawl, I found the following on the NGK site.

Mallory, MSD, Crane and Accel also produce a high output ignition CDI system, however, these should not be confused with a marine style CDI as mentioned above. For an automotive high output CDI system it is imperative you consult that manufacturer for plug specifications for their system. Some high out put systems specify the use of resistor plugs, while others will fry the internal plug resistor turning its 5k ohms into 60k ohms.

As a rule, performance is in no way impaired by resistor spark plugs. The only exception to this may be some models of high output CDI specify non-resistor plugs.

I am running an MSD with around 45 thou gap and I am just wondering if iy may be that the plugs have been cooked, especially as it had a bit of a session on the rig at Tims (makes me woder what the BHP would have ben with them firing properly).

Anybody got any knowledge out there and if you are a guru a good plug with a pretty well tuned motor. I will report further when I do a bit more research on MSD etc.

Any advice on plugs. Its combo is a Motown (chevy)415 with a level 4 (hot) crower cam and ally heads.

MIke