Wow. this is greek to me! I really want to try to understand this but am a bit of a loss where to begin. I do have a few questions already though, my 66 225 sl6 valiant has the CAP system on it, and it's ignition was upgraded to the mopar electronic ignition with a 76 distributor. How does all this affect the vacuum curve? Is my 66 missing out on some fuel economy due to a differing vacuum curve? I did replace my vacuum advance with the 76 advance(it is a 76 distributor, #3874598), it has an 8.5 on the arm of the advance.

It depends......what mileage are you getting now?
If your already at 21.5 for local and 25+ on trips don't worry about it. If not, then there may be some improvements you can make through recurving the distributor. See "Recurve Threads" in the Engine FAQ. Also see http://www.slantsix.org/forum/viewtopic.php?t=38471 and http://www.slantsix.org/forum/viewtopic.php?t=38465

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I'm lower than that..around 14 mph in the city.