Race Prep Performance

Highly recommend this shop for any type of specialty automotive needs from mild to wild. I have built a lot of high horsepower vehicles with different shops that have really taken me to the cleaner sadly, this is the first time a shop has actually dialed me back a little bit and was honest with me on what I really needed and didn’t need to save money, but get pretty much the same results and accomplished the goals I was going for. The owner is extremely down to earth, humble as can be, takes the time to explain any question you ask, whether you are first starting out building a car or you are a full on expert with a 1200 hp vehicle, you’ll be treated the same, and that is unheard of in today’s age. I just had them complete an E-85 package on my hellcat, as well as complete a bunch of maintenance work, they had the engine out of the car and back in, in legitimately one day, I had them throw a cam in it also, so the engine needed to come out. Not only how they’ve been fast and easy to communicate with, they are performing high-quality work and taking the time to make sure they’re doing a great job. I have been working with him now for years, and will continue to take my vehicles to them!

I rarely write a review about a product, person or service unless I truly feel that I received an exceptional product or exceptional service. In this case I did receive both; exceptional products along with exceptional service; an engine and transmission rebuild from Zach Brennan-Mueller, Race Prep Performance in El Mirage, Arizona. Back at the end of 2013, I ordered a 2014 Chrysler 300 SRT and a year later I threw away my remaining warranty and installed a Whipple supercharger and long tube headers. This combination I loved and I love that car. Well, in about 2020, it started using some oil, dripping oil and acting “weird” so I saved my money and in 2025 I did a lot of research and found a very reputable engine builder, Zach Brennan-Mueller of Race Prep Performance and selected him to rebuild my engine and other stuff. My engine did suffer from popped piston tops along with other issues. Zach built my engine to withstand 1000 horsepower! Jon Sipple of Sipple’s Speed and Performance, rebuilt my NAG 1 transmission with upgraded parts and Zach installed a Flyin’ Ryan Tomahawk camshaft as part of my build. There is a ton of new performance parts in that engine and car! Zach would regularly call me to check in and provide me progress updates, issues he found and other recommendations. He was great to work with! And best part yet is that he put up with me! My car screams now! It is scary! It was pretty good before with a dyno rating of 650 RWHP and over 600 foot pounds of torque. I’d love to get it on a dyno now just so I would know, but Ryan and FLyin Ryan Performance etimated it at around 700 RWHP from similar builds and tunes he has done. I cannot say enough good things about Zach or about how well my car is running. I am a very happy camper!

I will start with this… I’m not one to write reviews… I met Zach in 2022… found him on line searching for upper / lower control arms for my 2018 charger. Talked to him on the phone, he was willing to order the parts without a deposit and a day was scheduled for install. I’m about 3 hrs from his shop… arrived and he immediately starred working on it knowing it was a turnaround trip for me…non stop, no lunch break, drove to alignment shop and wrapped up in about 6 hrs….all for a very good price, quality parts and work…fast forward 2 years…. Time to build the motor…. Talked to a few shops in the Phoenix area… got quotes etc… just no one had the same vibe I got from Zach… the other shops wanted to build it their way, not mine…. Called Zach and he gave me probably 4+ hrs of phone time over a few days of questions, suggestions, ideas still not knowing if he was going to get the job…. Well he did… and I am so very happy with the build…. This is my 4th built vehicle and the BEST experience of them all…. From the personal “I’m never to busy to take your call or call you back” to suggestions, ideas and taking personal interest in what you want to accomplish with your build. I had my ideas, along with Zach’s extreme knowledge in Mopars…. I now have a very dependable daily driver fully built motor. During the entire build process constant communication from Zach about how it was going along with time estimates… total time from drop off to pick up…. 2 weeks…. and the entire time my vehicle was stored inside his locked shop ! I couldn’t be more satisfied with the quality of his work, not 1 issue since receiving my car back. Everything turned out absolutely perfect !!! I’m not a personal friend of Zach’s….. strictly a business relationship with him… if he would have done a bad job, this would read completely the opposite… So if your a Mopar owner looking to gain just a few HP or a lot of HP…. I really don’t think you will find a better place or person to go to. Zach is very honest, very knowledgeable, keeps you in the loop and delivers what he says when he says it !!!

I went to Race Prep to get a cold air intake, exhaust, lowering springs and adjustable controls arms. Zach does great work and is easy to work with ..

Great guy to work with!