pw520a 19 Report post Posted March 12, 2011 I am in the process of installing new plugs for my rebuilt 390, The plugs are very hard to get to so I want the longest lasting plugs I can buy, any recomendations? The auto parts store recomended autolite platinum ap 45. They came with a gap of 044 my distributor does not have points, would this be the correct gap for the 390? the plugs that came with the 390 were gapped at 035 maybe that was for points I am not sure. any advice would be appreciated. thanks Quote Share this post Link to post Share on other sites
pw520a 19 Report post Posted March 12, 2011 I am in the process of installing new plugs for my rebuilt 390, The plugs are very hard to get to so I want the longest lasting plugs I can buy, any recomendations? The auto parts store recomended autolite platinum ap 45. They came with a gap of 044 my distributor does not have points, would this be the correct gap for the 390? the plugs that came with the 390 were gapped at 035 maybe that was for points I am not sure. any advice would be appreciated. thanks Quote Share this post Link to post Share on other sites
LindenBruce 27 Report post Posted March 12, 2011 The points are not the deciding factor on plug gap, your coil output is. The wider the gap is the more current it takes to fire the plug. If you have a high output coil you are fine with a .044" gap. If you are using the factory 15,000-20,000v coil stay with the smaller .035 gap. Also, because the way spark plugs point up on an FE in a valley, apply a light coat of never seize to the threads of your new plugs. That will make them much easier to remove next time. And use a good platinum or better spark plug for long life. Good luck on changing those plugs!!! :) Bruce Quote Share this post Link to post Share on other sites
LindenBruce 27 Report post Posted March 12, 2011 The points are not the deciding factor on plug gap, your coil output is. The wider the gap is the more current it takes to fire the plug. If you have a high output coil you are fine with a .044" gap. If you are using the factory 15,000-20,000v coil stay with the smaller .035 gap. Also, because the way spark plugs point up on an FE in a valley, apply a light coat of never seize to the threads of your new plugs. That will make them much easier to remove next time. And use a good platinum or better spark plug for long life. Good luck on changing those plugs!!! :) Bruce Quote Share this post Link to post Share on other sites
pw520a 19 Report post Posted March 12, 2011 The coil I have is a flame thrower 1.5 ohm petronix. do you think that is right for the 045 gap. Thanks Bruce I appreciate your input Gary Quote Share this post Link to post Share on other sites
pw520a 19 Report post Posted March 12, 2011 The coil I have is a flame thrower 1.5 ohm petronix. do you think that is right for the 045 gap. Thanks Bruce I appreciate your input Gary Quote Share this post Link to post Share on other sites
LindenBruce 27 Report post Posted March 13, 2011 Yeah that should be fine. That's like a 40,000v coil right? The 1.5 ohm resistance means it won't recharge as fast between sparks relegating that coil to a single spark per timing event. Their flame thrower III has like a .38 ohm resistance meaning it recharges faster and is capable of multiple sparks per timing event. Bruce Quote Share this post Link to post Share on other sites
LindenBruce 27 Report post Posted March 13, 2011 Yeah that should be fine. That's like a 40,000v coil right? The 1.5 ohm resistance means it won't recharge as fast between sparks relegating that coil to a single spark per timing event. Their flame thrower III has like a .38 ohm resistance meaning it recharges faster and is capable of multiple sparks per timing event. Bruce Quote Share this post Link to post Share on other sites
