[71 Red Sled]

Why did my enigine builder tell me not to run vacuum advance on my engine? It is a 450 hp 383ci.

Also should I convert the disrtibutor I have to electronic ignition or should I buy a new distributor.... Keep in mind this is in a 1971 vette so the distrbutor has the tach drive so it is pricey.

[lluciano77]

I would run vacuum advance unless you have really high compression. I have 11:1 on my car and vacuum advance would not work well.

He said that because race distributors are all mechanical. Don't listen. Just recurve your vacuum distributor for more performance.

[firechicken383]

If this engine will see street use, you need the vacuum advance. It helps part throttle drivability and gas milage. The reason race engines dont use it is because they dont need it. At wide open throttle , you dont get vacuum advance.

[TurboS10]

I think what you are going to find is that an engine putting out that kind of power is going to need a high initial advance. This is a problem with oem distributors since they have a set total advance. Basically you either need an aftermarket unit that can have the advance tuned or devise a way to limit advance on yours. Vacuum advance only effects cruise and part throttle. If set properly along with total mechanical advance it should not cause you any problems. It is really just for mileage as listed above, but it will also help with response a little bit when transistioning from cruise to WOT.

Chris

[Frisco]

Originally posted by 71 Red Sled
Why did my enigine builder tell me not to run vacuum advance on my engine? It is a 450 hp 383ci.

Unless your intended use is "Drag Race Only", your engine builder told you not to run vacuum advance because he doesn't know how it works or how to set it up correctly .

Read the earlier posts for correct info.

[jimfulco]

Full throttle on the track, but not in the pits. Vacuum advance will make it run a little smoother when you're not racing.