Looking for opinions on which spark plug to run in a 10.80 street/strip car with Stage 2 Street Eliminator heads. Single plane intake, MSD, 308s cam. Any suggestions would be appreciated.
AT 10.8 to 1 I would use the NGK FR5, just like we do in all the street motors.. around 10.5 compression. That's the 5/8 hex 3/4 inch reach projected tip V-power plug, stock number 7373 when you order. If you want something colder, then we go to the NGK R5672-8 stock number 7173. I only use NGK plugs in aluminum heads, because they are plated, and resist corrosion. do not put anti-seize on them. It inhibits the transfer of heat from the plug to the head. Plated plugs will not seize up in the head. JW
Thanks Jim. I don't know the actual compression ratio as the motor was in the car when I bought it. I'm guessing it's between 11-12 to 1 since I was told to mix a little race gas with pump premium. So do you recommend the NGK R5672-8 stock number 7173 since it is likely higher than 10.8 to 1? BTW, the Viton rear main seal and the gray Great Stuff worked very well. No leaks at all so far with 15-20 miles of driving. Thanks again for the help.
James, Yes you can run the colder plug with unknown compression.. Also, with a big cam, a multi spark ignition (MSD 6AL) is the key to keeping the plugs clean during cruising around. Open the plug gap up to .045 with an MSD or similar ignition system. JW
I would run whatever plugs are going 10.80s or what Jim says. It sounds like something must be working. Bob H.
There is some great info in here James. As far as gap goes rule of thumb plug gap COMPRESSION GAP UP TO 10.5:1 .040 - .045 10.5:1 - 13:1 .032 - .040 OVER 13:1 .025 - .032 I set most stuff at .035