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spark plugs

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Grampy

Grampy

Freshman Member
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I think I need hotter plugs for my 1275, cam , 40 over pistons, comptune SUs I have lost the plugs the car cam with I would appreciate recommendations for spark plugs.
Thanks
 
My recomendations:
NGK BP6ES for Stock up to 10.0 to 1 Compression
BP7ES for LPHP engines (11.0) or after 10.0/1
BP8ES for 12.0 and over
BP9ES for 13.0 and over
BP10ES for 14.6 and over

The B"X"ES and B"X"EV (X denotes #) are corresponding part numbers for non-extended nose plugs and fine metal wire electrode applications. The 1275 seems to like the projected nose plugs a little better and has the necessary tip clearance. 948's and 1098's with domed pistons usually use the regular nose plugs with spacer washers to get tip clearance.

All these spark plug recommendations are caveated with the appropriate timing settings to go along with them. Stock timing for stock applications. LPHP engines usually don't go over 32 degrees at 7K rpm. 12.0 and up engines stay closer to or right on 30 degrees BTDC for thier coresponding 8K and up range.

Autolite, Denso and Champion have cross overs for these heat ranges. I use the Autolite AR51's in my LPHP a good bit. You can get these NGKs at most every "Box" autoparts store locally.

HTH, Mike Miller
 
One additional thought.

It is always better to start out too cold versus too hot. Too hot plugs can lead to detonation and/or pre-ignition. Detonation and pre-ignition do bad things to piston tops and ring lands. Too cold a plug just results in fouling, but nothing is impacted other than the plug. For NGKs, the higher the number the colder the plug. Changing plug heat ranges results in approximately a 75 - 125 degree F difference in tip temperature. Sparkplug design might affect the actual number, but this range is close.
 
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