Fitting a Blow Off Valve the right way (ST185)

By Robert Pina

Picture courtesy Kriss Graham

I have noticed that most people use the standard small nipples on the left side of the intake manifold. While this does work, I have found trough much testing that using a larger diameter feed from the intake manifold increases the response and the performance of the bov. Since the bov responds to vac and boost, creating a stronger signal will help it tremendously. Using skinny vacuum lines, connected with the boost gauge will not give the bov the amount of signal it would like to have.

Also you will notice that most performance bov's have a LARGE diameter nipple for the air feed which will match with my version of the process. -RP

There are 2 nipples located on this side which can provide vacuum boost. They are of a smaller size and a perfect fit for most boost gauges. Not the best source for bov vac/boost.

On the right side of the ST185 manifold, right at the edge of the tank, you will see a large hose coming out of the plenum and into another device. This hose is of a larger diameter than standard vac/boost lines, which will give the bov the greatest response. On ST165 this hose is at the rear of the intake manifold. It may also be a good time to replace this hose. It is usually hard and cracked. Universal rubber hose from your local parts store should work just fine.

This of course is where the bov will reside (ST185). An aluminum flange will need to be welded to this spot. Take care when selecting your bov, as a unit too large will contact either the intake piping or the radiator hose. A mock installation before welding would be a good idea to make sure it's clear.

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