Coyote-Swapped Fox Hydroboost Made Easy With Maximum Motorsports

As someone who has personally attempted a Hydroboost conversion in a Coyote-swapped Fo­x-body, I can tell you that it is not a fun project without the correct tools. Back in 2014 when I made my attempt, there wasn’t much information out there, nor were there parts available to make the process easy. Those attempting a Coyote-swap with Hydroboost today are in luck! Maximum Motorsports now offers two Hydroboost conversion kits for Fox-Coyote swaps, adapting 1996-1998 and 1999-2004 Hydroboost units into 1979-1993 Mustangs  (PN: MMBAK-19, MMBAK-20). The kits retail for $239.97 and $249.97 respectively. A compatible brake line kit is offered separately.

Maximum Motorsports’ Hydroboost Conversion Kit, 1999-2004 Hydroboost in 1979-1993 Mustang

If you’re not familiar with the reasons behind going the Hydroboost route, allow us to explain. Swapping a Coyote or a 4.6L modular engine into a Fox-body leaves no room for a vacuum brake booster. Most people would prefer to drive a car with power-assisted brakes over manual brakes, so a Hydroboost conversion is the perfect choice.

The Hydroboost system also provides superior brake response regardless of engine vacuum, making for a seamless pedal feel without the inconsistency felt with vacuum-assisted brakes. It also negates the issue of some pushrod engine cams that don’t allow the creation of enough vacuum to operate a vacuum brake booster at idle. Finally, Hydroboost leads to low brake pedal effort, even when used with small-diameter brake rotors.

Your kit will come complete with a firewall adapter block, brake pedal, pedal box spacer, and the required tools for installation. The firewall adapter block is constructed of billet aluminum and mounts the Hydroboost unit at the proper angle, height, fore/aft locations, and lateral location so that it performs as it was designed to in SN95 Mustangs. Its mounting studs line up with the Fox firewall hole pattern for easy installation. The brake pedal is made of alloy steel. Its pushrod pin location allows it to match the brake pedal ratio and pushrod geometry of its native Mustang. This design promotes correct pedal travel and effort and keeps the master cylinder from being over-stroked. The billet aluminum pedal box spacer is provided to replace the stock plastic spacer located between the firewall and pedal box that is prone to breaking. Finally, the tools include a special MM-designed socket to remove the giant nut that secures the Hydroboost unit to the stock firewall mounting plate and install it onto the included aluminum firewall block, and a second tool (1999-2004 Mustang Hydroboost kit only) that modifies the firewall hole for the master cylinder pushrod. The Hydroboost unit itself is required but not included.

The Hydroboost Conversion Kit works with most of the front and rear caliper setups used on Fox-body and SN95 Mustangs. For more in-depth information (seriously, Maximum Motorsports’ website information is second-to-none), visit

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About the author

Stephanie Davies-Bardekoff

Stephanie Davies-Bardekoff got her start in automotive media while attending Rutgers. She worked for Roush Performance for a while, before eventually landing here at Power Automedia. Her Coyote-swapped 1992 Fox-body drag car is her prized possession.
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