moparchris
Well-Known Member
Hey Roadrunner69,
I too have run the 509 on a 8 to 1 440. It too smoked like a cuban cigar at idle. That cam has horrible idle vacuum. Two things I did to make it more livable. First off with a stock Holley ( I assume thats what your running) the power valve should be a 6.5. That means at 6.5 inches of vacuum it will open. Do the math and your car is idling with the power valve open! Ten jet sizes too big! This causes a real rich condition and cause it to load up the plugs, which will compound the problem. Holley sells as low as 2.5 power valves which will work because your vacuum reading will go up with the proper mixture. The second thing I did was lock out the mechanical timing. My car was an automatic and I could get away with it, your manual may ping and hate life if you lug it. So I would have the distributor modified to where you limit the amount of timing advance the distributor offers. I had an MSD billet and you just change the stop bushing. I recommend you limit your advance to around 10 degrees and then set your initial to 24-26 degrees as a compromise so you get the total you need. I would also disconnect the vacuum advance since all it does is move the timing around since your vacuum signal is so weak. You can also open the secondaries at idle to help balance out the idle circuit and let you close the primaries to cover the transfer port on the primaries. This will get you better mixture distribution in the cylinders at idle and help with any stumbling that you may have while acheiving the desired idle RPM. You can also run the primaries 2 jet sizes smaller to help out with the rich condition. One of the problems with ignition timing is it wanders around at idle creating low vacuum. The problem also keeps you from making any progress when adjusting the carb. If you have a carter, you may want to try a holley since it is way more adjustable than the Carters/Edelbrocks. The Carters are prone to running rich at idle. The 509 ran real good in my stock 440 in my Dart. It has a narrow power band but it really rocks when it is on.
I too have run the 509 on a 8 to 1 440. It too smoked like a cuban cigar at idle. That cam has horrible idle vacuum. Two things I did to make it more livable. First off with a stock Holley ( I assume thats what your running) the power valve should be a 6.5. That means at 6.5 inches of vacuum it will open. Do the math and your car is idling with the power valve open! Ten jet sizes too big! This causes a real rich condition and cause it to load up the plugs, which will compound the problem. Holley sells as low as 2.5 power valves which will work because your vacuum reading will go up with the proper mixture. The second thing I did was lock out the mechanical timing. My car was an automatic and I could get away with it, your manual may ping and hate life if you lug it. So I would have the distributor modified to where you limit the amount of timing advance the distributor offers. I had an MSD billet and you just change the stop bushing. I recommend you limit your advance to around 10 degrees and then set your initial to 24-26 degrees as a compromise so you get the total you need. I would also disconnect the vacuum advance since all it does is move the timing around since your vacuum signal is so weak. You can also open the secondaries at idle to help balance out the idle circuit and let you close the primaries to cover the transfer port on the primaries. This will get you better mixture distribution in the cylinders at idle and help with any stumbling that you may have while acheiving the desired idle RPM. You can also run the primaries 2 jet sizes smaller to help out with the rich condition. One of the problems with ignition timing is it wanders around at idle creating low vacuum. The problem also keeps you from making any progress when adjusting the carb. If you have a carter, you may want to try a holley since it is way more adjustable than the Carters/Edelbrocks. The Carters are prone to running rich at idle. The 509 ran real good in my stock 440 in my Dart. It has a narrow power band but it really rocks when it is on.