This page is designed to help you understand, educate, and decipher truth from myth in blown motor applications.

TOPICS:

	Pressure Relieve Valve
	Venting Front Gear Cover Voids Warranties

• Blower Pressure Relieve Valve 

    A pressure relieve valve is located on the front gear cover of a blower. The purpose or use of this design is to manually relieve pressure that accumulates inside of the front gear cover when a motor obtains boost. This is done by pressing the valve which in return, releases the pressure.

    There is a pretty big misconception of when the pressure relieve valve should be used. We all know that feeling of satisfaction one gets when burst of air gets released from his blower with all of his hot rod fanatics standing around the blown beauty. But in all actuality, the more times you press that pressure relieve valve, the worse it is for the blower. Before you start wondering, if this is true, why is it there in the first place? Well let's explain what is going on inside blower;

    When the blower produces boost in the motor, (oh, lets say 8 lbs) there is 8 lbs. of boost in the intake manifold, cylinder heads, piston chambers, and yes, also in the blower itself. Now, the way the front rotor seals are designed, they allow boost to enter into the front gear cover but not return. This actually puts back pressure on the seals, which in return, helps the sealing. Now you have to ask yourself, what is mixed with boost?..........You got it, Fuel. So when the boost enters into your front cover, you also get a small dose of fuel that mixes in with the 90wt gear oil. This is okay to a certain extent. The fact is, every time you release that pressure, the next time you make boost you will also add more fuel to the 90wt gear oil, thinning it out more and more each time. When the weight of the oil gets to thin, then this can cause excessive wear in the gears and front bearings.

So when should you use the pressure relieve? 

• If you are going to remove front gear cover or the blower drive assembly.

• If you are going to change or add gear oil.

• If you anticipate not using your motor for a month or longer.

• When your strictly drag racing. Anything goes in this category. Anytime you feel you need to let the 40lbs of boost off of that poor front cover gasket.  

    If the motor is going to do nothing but sit over a period of time, let's say winter, then it is a good idea to let the pressure out to help extend the life of the front cover gasket.

• Venting Front Gear Cover on a Blower Voids Warranty

    In some cases, you may see a blown motor with a line running from the front gear cover to the valve covers, oil pan, or some other place on the motor. Some times you will also run into someone supplying the front cover with the oil from the engine. You do not ever want to associate the 90wt gear oil with engine oil in any way with an aftermarket blower unit. You also never want to vent the cover to consistently release pressure out of it. If you read the article on "Blower Pressure Relieve Valve" you can understand how bad this can be for the blower, not to mention the consistent loss of pressure.

Venting the front gear cover usually voids the warranty with just about any blower company.