What would be the best spark plug to use in my 451? Engine specs are: 14 cc dome pistons, 915 heads at 80 cc, 509 cam, 292 duration int and ex. 3.91 gears auto trans. 2400 RPM stall torque converter. C/R right at 13.3 to 1. Altitude, 5400 feet, Mostly strip use, some street. Holley Street Dominator intake. Holley 3310 carb vac secondary. Currently using RJ 12 Y C Champions with the 88 cc heads that are on it, ported 906 @ 12.5 to 1 C/R. 100 Octane Sunoco fuel.
Garys69RR If your running at the track you can go 1 or 2 steps colder in Spark Plug Heat Range. Just watch the plug color. Your looking for a Gray or Ash color. White or a color you can't really read or see is NO GOOD.. I like a .032 to .035 cap, even with a good ignition. It gives the plug time to cool and the Coil time to get charged for the next cycle. You didn't mention timing. 12* base timing. 32*-34* total. Have it all in before 2600-2800rpm. More timing if it like it and your engine isn't pinging. Are you really a Champion Plug Brand user or are you open to suggestions on other brands.
Garys69RRIf your interested in changing brands of spark plugs. NGK has a V-Groove NON RESISTOR spark plug. Autolite also makes a very good spark plug for racing. I don't believe in a $9.00 ea. spark plug. Thats crazy unless someone is giving them to you...LOL...Your application set the Plug Gap @.032-.035The parts below are at Jegs'. P/N 739-R5670-10 Cold P/N 739-R5670-9 Med/HotP/N 739-R5670-8 HotJegs price was $2.69 ea or a Box of 10NOTE:..NGK Spark Plugs Hot #8-#9-#10 (#10 Cold is What you want for racing, and it's NON Resistor). They are a good spark plug for racing. Then you can always change back to the street plug. If you want. Bob
MERRY CHRISTMAS TO ALL THE M,M,M Guys...Bob
Ok thanks for your help! I will try the NGK plugs when I install the 915 heads. And total timing is at 18 initial, 36 total. Seems to work well for me. This motor likes alot of initial advance. Prob due to the 5400 feet elevation.
Gary your welcome. When your making good horse power they love timing. As long as you have the good gas to support it they run like the tail-pipes are on fire (a kittle play on words)...lol... Don't be suprised some night your at the track, and its a little damp, and cool. You'll see timing (just speaking in general) you may see your total timing at 42-44 degrees or more. Gary I use this as a rule of thumb: An automatic can go usually (1)step colder in spark plug heat range. Because your actually lugging the engine to stage. On a 4 speed car you can go (2) steps colder in spark plug heat range. It's obvious you can push the clutch in and rev the engine to keep the plugs clean. Set the gap .032-.035. Do you know how to index your plugs? There's afew more HP there... NGKs a good spark plug. My brother has a Harley something. Sorry I'm not a bike guy. When he starts the engine and drives it the will the engine will miss until it gets to operating temp. I've riden it it's dangerous. You can't give it any gas, it just dies. The dealer where he bought it couldn't figure it out. Good Luck. The NGKs are no more expensive than a resistor plug.But I did. It was the cylinder closest the exhaust that was Okay. The cylinder sitting out in the open air flow was the problem. I went (1) step warmer on a spark plug, and no more problem. Bob