Do I need a vacuum advance distributor?
Vacuum advance distributors are best for street vehicles. The vacuum advance feature has NO EFFECT on full-throttle power. They provide no benefit for engines that spend most of their life at high rpm (race engines). A vacuum advance unit can add up to 15 degrees of advance.
Why do distributors have vacuum advance?
As an engine revs up, we need to allow even more of a head start for the spark plug in order for complete combustion to occur. For this reason, a mechanical advance is built into most distributors.
What is a mechanical advance distributor?
The mechanical (or centrifugal) advance is an Ignition Timing control mechanism built into most distributors. It is made up of: Two weights, An advance plate or cam attached to the trigger mechanism inside the distributor, and. Springs that control how fast the weights are flung outward.
Do all distributors have mechanical advance?
Not all distributors are equipped with vacuum advance, but for a street engine it can be very useful. Engines operating at part throttle require more ignition timing to light the fire in the chamber because the cylinder contains only a portion of the total charge that is present at wide-open throttle (WOT).
What happens when vacuum advance fails?
Eventually the deterioration will reach the point that the vacuum advance no longer adjusts the timing, causing the vehicle to hesitate when the engine attempts to move the vehicle’s weight. In addition to this lack of power, a vacuum leak can also cause the engine to idle roughly or even stall.
Do I need vacuum advance with MSD?
On all but the most radical street engines, vacuum advance will improve the way the engine runs. The MSD 8361 has the vacuum advance that you’re looking for. The 85551 is very popular so you could easily sell it to recoup some of the cost of the 8361. I hope this helps.
Does vacuum advance go to ported or manifold vacuum?
At idle, the engine needs additional spark advance in order to fire that lean, diluted mixture earlier in order to develop maximum cylinder pressure at the proper point, so the vacuum advance can (connected to manifold vacuum, not “ported” vacuum – more on that aberration later) is activated by the high manifold vacuum …
What is a vacuum advance on a distributor?
Vacuum Advance 1 Definitions. Mechanical advance uses the weights and springs in the distributor to rotate and alter the timing sensor shaft’s position relative to the engine’s position. 2 Speed. Mechanical advance activates only during high engine rpm, which causes the distributor to rotate quickly enough to activate the advance. 3 Advantages.
What is the difference between mechanical advance and vacuum timing?
Mechanical advance activates only during high engine rpm, which causes the distributor to rotate quickly enough to activate the advance. Vacuum timing senses changes in the engine’s load, or the demand placed on the engine for power, and offers greater timing advance during low loads.
Mechanical advance distributors, which sense only changes in rpm, are meant for special purpose applications, such as as drag racing or poorly designed multi-carb set-ups…. or moving a loaded Type II with a 25hp engine.
What is the purpose of a VAC advance?
The vac advance is an addition to the mechanical advance. The mechanical advance works and doesn’t care where the throttle is, what load is on the engine or anything but rpm. More for flat out performance and consistency. The vac advance does all of that plus !!! Allows the engine to run cooler by advancing the timing.