Vaccum Adv Timing
12-17-2008, 08:23 PM
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Vaccum Adv Timing I just bought a new distibutor from msd with a adjustable vaccum advance.Anybody on here run on these distibutors?It is there Street Fire series they sell.Im curious on where i should expect to set the advance on it.I have a 355 sb with a mild street cam ,headers,double hump heads and dual plane intake.Nothing real crazy.I have no idea how to set the advace on a engine so any help would be great.
12-17-2008, 10:40 PM
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The vacuum advance is only under part throttle under normal driving conditions to make a bit more economy, but engine initial and total advance have to be set/checked with the engine running, vac advance disconnected and plugged at the carb, you check initial, usually 14-16* for me and rev the motor to 2500 RPM and check total, around 34-38 depending on the engine and what it likes.
12-18-2008, 11:31 AM
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As ZONES89RS states, you will want to first set the initial timing. Do this with the engine warmed up (off of high idle speed). Unhook the vacuum advance and use a timing light to check the timing. You are going to want around 12* advance (give or take). With the vacuum still unhooked, rev the engine and see where the timing goes to at maximum mechanical advance (you should have an adjustable timing light). I am not sure if that MSD has adjustable mechanical advance...the directions should say. Lastly, adjust the vacuum advance by turning the allen screw (inside the vacuum connection nipple) all the way in. Back it out 1 turn. This is where you should start (it is the minimum vacuum curve). You can increase the vacuum advance by backing out more turns. You'll need to fiddle with these three things (initial advacne, mechanical advance and vacuum advance) to get things perfect. Just don't over do it!
