Belt driven fans work best when they are 3/4" to 1" from the radiator's surface. Whenever you remove an original equipment fan clutch from your engine, you need to add a spacer to bring your new fan back into the "sweet spot" in the fan shroud opening. Use spacers according to the applications listed for stock engine set-ups. For engine swaps, check the clearances in your engine compartment and select the spacer(s) you need accordingly. Multiple spacers may be used, up to a maximum of 3".