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What about the Harry high-school non-vacuum advance polished billet "whiz-bang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.
Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; low vacuum advance cans are available (from real ignition company's) to provides the same amount of advance as the stock can (15 degrees), but are fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam.
For peak engine performance, drivability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don’t understand it, they're on commission, and they want to sell "race car" parts." end Quote.
A few notes from over 100 years of the combined experience of Jim and myself in tuning, setting up distributors and developing our own computer controlled Mopar ignition systems:
*The adjustable vacuum canisters only adjust the sensitivity of the vacuum can, not the stroke.
*Limiting the mechanical advance and increasing idle timing to be compatible with today's fuel formulations are a necessity that can not be overlooked.
*Beware of the Imported distributors that appear to have the hex shaped vac cans that should designate it as an adjustable vac can, many are not. (Spectra is the worst)
*Any one who tells you that the vac can is not needed with their ignition system or distributor is playing on your lack of knowledge and probably needs to read this article so THEY understand how UN-knowledgeable their statements make them appear or maybe their just trying to increase profits at your expense? Non adjustable vac cans out of China are about $2 a good quality adjustable can is probably closer to $10-$15 to build.
*Last comment beware of the "Snake Oil", our industry is loaded with false and rediculous performance claims, misinformation, country of origin claims, repackaging to hide source and vendors with very little knowledge of how their products really work and why. When you want reliable information go to the guy who engineered it and makes it.
*Our products are all designed in house, manufactured and assembled in the USA and most components are made by ISO 9000 compliant vendors.
*ISO 9000 is a quality management standard that presents guidelines intended to increase business efficiency and customer satisfaction. The goal of ISO 9000 is to embed a quality management system within an organization, increasing productivity, reducing unnecessary costs, and ensuring quality of processes and products.
What about the Harry high-school non-vacuum advance polished billet "whiz-bang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.
Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; low vacuum advance cans are available (from real ignition company's) to provides the same amount of advance as the stock can (15 degrees), but are fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam.
For peak engine performance, drivability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don’t understand it, they're on commission, and they want to sell "race car" parts." end Quote.
A few notes from over 100 years of the combined experience of Jim and myself in tuning, setting up distributors and developing our own computer controlled Mopar ignition systems:
*The adjustable vacuum canisters only adjust the sensitivity of the vacuum can, not the stroke.
*Limiting the mechanical advance and increasing idle timing to be compatible with today's fuel formulations are a necessity that can not be overlooked.
*Beware of the Imported distributors that appear to have the hex shaped vac cans that should designate it as an adjustable vac can, many are not. (Spectra is the worst)
*Any one who tells you that the vac can is not needed with their ignition system or distributor is playing on your lack of knowledge and probably needs to read this article so THEY understand how UN-knowledgeable their statements make them appear or maybe their just trying to increase profits at your expense? Non adjustable vac cans out of China are about $2 a good quality adjustable can is probably closer to $10-$15 to build.
*Last comment beware of the "Snake Oil", our industry is loaded with false and rediculous performance claims, misinformation, country of origin claims, repackaging to hide source and vendors with very little knowledge of how their products really work and why. When you want reliable information go to the guy who engineered it and makes it.
*Our products are all designed in house, manufactured and assembled in the USA and most components are made by ISO 9000 compliant vendors.
*ISO 9000 is a quality management standard that presents guidelines intended to increase business efficiency and customer satisfaction. The goal of ISO 9000 is to embed a quality management system within an organization, increasing productivity, reducing unnecessary costs, and ensuring quality of processes and products.
