Expert: Ray Hawk - 12/1/2009

Question
I have 1983 chevy K5 blazer 350 5.7L. My distributor has no vacuum advance. I purchased a new HEI dist. specifically for my blazer and the one that they sent me has a vacuum advance. What is the difference?  

Answer
Hello Angela,

On some cars with distributors, the distributor will have an input for a vacuum hose. When the vacuum in the intake increases or decreases, the distributor rotor will advance or retard, adjusting the spark plug timing for best performance. However, the vacuum advance is not always necessary; the distributor you recieved may have been built to fit a number of Chevy 5.7's, some with and some without the vacuum advance; you have the one without it. They may or may not have sent you a plug for the vacuum hose input; if they did, simply use the plug(s) to cover the input(s) and you should be all set. If they didn't send you the plugs, you can buy them in packs almost anywhere. They're cheap, so don't worry about spending too much money. However, if your distributor was made specifically for vacuum advance, and cannot be use with a non-vacuum-advance car, then send it back to where you purchased it and ask for the distributor without vacuum advance.

Hope this helps you!

-Ray A. Hawk