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caldy
09-09-2003, 05:12 PM
i have a 351w w\a 6a module, 8478 pro billet dist., super conductor wires & blaster ss coil. i had trouble dialing the advance curve in. the largest bushing supplied advanced timing to far. i ended up making a custom bushing to limit the mechanical advance to 12 degrees. i start at 12 degrees initial, the mechanical takes it to about 24 & then the adjustable vacuum takes it up 4 more for a total of 28. anything more than that starts to ping on the top end. bottom end w\this setup could be a little better. top end is real good. i would like to bring it up just a couple more degrees initial for a little better bottom end. i can do that if i eliminate the vacuum advance but then i lose some driveability. would being able to phase the rotor help me w\this problem at all. i'm going to be replacing my cap & rotor w\a cap-a-dapt 8441 & was wondering if there would be a benefit w\the 8420's phasing ability? also i have plugs opened up xtra .004. would going narrower or wider change where the pinging occurs or even help eliminate it? thanks for your help, caldy.

msdtech1
09-10-2003, 10:58 PM
Rotor phasing will not help with the issues that you described. To start, the 4 degrees of vacumm advance that you mentioned is only added to your total timing when vacuum is present. At the engine is at wide open throttle or under a heavy load (where pinging normally occurs at) you should not have any vacuum present and therefore your total timing is only 24 degrees. Vacuum advance is designed to improve idle charateristics and part throttle engine responce when sitting at a stop light or when you lightly accelerate from the light. There are many things that cause pinging, ie. high compression, fuel octane rating, engine temperature, air/fuel ratio, engine load, etc. If your engine is pinging with low timing you may want to look at why it is pinging or run a higher octane fuel.

MSD Tech1

caldy
09-11-2003, 10:35 AM
thanks for the reply. i did a little more checking through this forum & found i have my vacuum advance connected to a ported supply instead of manifold supply. i reconnected to a manifold supply. also found a lean jetting condition w\carb & went 1 size bigger in jets & was able to bump up initial timing another 4 degrees. now i have the bottom end i was looking for & still have great top end. pinging has gone. my other? is that i'm ordering the cap-a-dapt setup & would like to know if it is worth getting the 8420 & phasing the rotor or just stick w\the 8441? after about 12,000 mi. i've noticed the little contact ball up top of cap is worn all the way down to flat & the terminals inside cap are burnt pretty good on the leading edge & there is some gray film in between contacts of terminals throughout the cap. i checked the plugs when i checked for the lean condition & i made a mistake on my first post as i have the plugs opened up an xtra 10 thousands instead of 4. also does the gap tend to make a difference on the top or bottom end? could plugs being to big or to small a gap be burning the rotor & cap up that quick? it seems to me that i should get more miles out of a cap & rotor than that. thanks for the help, caldy.

msdtech1
09-11-2003, 11:29 AM
Looks like you are headed in the right direction. Usually when the center carbon ball in the distributor cap starts failing it is caused by the rotor tang either being bent or not making good contact with the carbon ball. If the tang is bent or the carbon ball was damage during installation the ball will deteriorate extremely fast. A larger plug gap will create more demand on the secondary components like the coil, cap, rotor an coil wire, so you must watch these carefully if you run a larger gap. MSD recommends running a plug gap that is .005 larger than the recommended stock plug gap recommendation.

MSD Tech1

caldy
09-11-2003, 11:39 AM
thanks for the quick reply. i'll pay attention to the rotor tang when i install new cap & rotor. i'll also reduce plug gap to .005 over stock. i take it phasing the rotor is not a big deal w\my setup. if thats the case i'll just order the 8441 cap-a-dapt. again thanks for the help, caldy.

msdtech1
09-11-2003, 11:05 PM
Your welcome.

MSD Tech1