Vacuum Advance Question
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Freshman User
Joined: Apr 2004
Posts: 28
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From: Richmond, KY
Vacuum Advance Question
I have a fresh 514 stroker and I installed an Edelbrock 750cfm carb this weekend. During the carb install - I changed the distributor (standard distributor) vacuum advance to the ported opening on the carburetor. The guy who put the engine in for me recently had it routed to manifold vacuum. Now I seem to have hesitation coming off idle and I never had this problem before. Should I simply switch vac back to manifold or should I check timing?? Any thoughts/advice appreciated. Thanks.
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I prefer the mainfold vacuum. It causes the engine to idle faster so the throttle butterfly's have to be closed more to maintain the original idle speed this gives you more engine vacuum at idle and helps some when running a bigger cam by improving the idle characteristics. Another advantage is the engine will run cooler.
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Freshman User
Joined: Apr 2004
Posts: 28
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From: Richmond, KY
Thanks wvbogger. I didn't want to write a book earlier -- but my truck ran a bit hotter also which goes along with your comments. Based on comments I saw in the forum and the Edelbrock instructions - I thought it prudent to change to the ported vacuum. Guess the old rule of if it ain't broke don't fix it applies. I will switch back to manifold vacuum and see if it works ok.
Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
Vacuum advance was created to increase gas mileage at cuirse speeds, not jack up initial ignition timing at idle. You are suppose to shorten the mechanical advance curve to do that. Has your dist. been recurved and if not, why not? What is you total maximum mechanical advance?
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Freshman User
Joined: Apr 2004
Posts: 28
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From: Richmond, KY
bear 45/70 -- good questions and they are a bit over my head. I believe the answer is no the dist hasn't been recurved. After driving the truck more today I'm thinking my problem pertains to fuel delivery. I put a new fuel filter in as part of putting the new carb on and the thing acts like it's clogged up or something. I'm taking truck to a shop tomorrow to have a friend check timing and fuel filter/lines.
