Been here a few times now. Ryan is always super friendly and helpful. He was quick to answer all of my questions and knows his stuff. His shop is very impressive. Has all the tools to do the engine work correctly. Would definitely recommend. Remember quality work isn't cheap. So don't come here if you're cheap. His work is top tier quality. read more

Big thanks to Ryan at JGM performance engineering! Had a bare ford 302 block machined, assembled, and dynamometer all at JGM. Ryan is super knowledgeable and was able to lead me in the direction I needed to go for my application. Thanks to the guys at JGM I have an awesome turnkey engine. If you looking for a shop that can build you a performance turnkey engine this is the place I recommend. read more

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I took a nice used Jeep 258 in to be rebuilt, balanced and the cylinder head milled 0.060". I asked that the head not be installed . I wanted the inspect the work before installation. Everything looked good. Upon installation, I discovered a crack in the side of the block, close to the water pump.. They had charged me for thermal cleaning and magnafluxing the block and head for cracks. When I told JGM about the crack they told me to remove the engine and return it for repairs..... I informed them they needed to give me the tooling to repair the block in chassis. I did repair it myself. The engine took a while to break in but runs very well. Screwups like missing a cracked block can ruin a business. I hope they learned. read more

JGM Performance Engineering - Auto Customization Near Me - Valencia, California

This is a true, custom engine building performance shop. If you are looking for extraordinary performance enhanced engine experience... Look no further. Ryan is meticulous with his attention to detail with respect to machine work down to expertly engine assembly. Ryan and his staff have built and dyno tested two engines for me. My first engine was a 327 CI Chevrolet which produced over 450, reliable, HP! No full engine build leaves his performance center without being fully blue printed. He highly recommends for all engine builds to be dyno tested which is done in house! On my second engine build, 327 CI punched to a 331 CI, made over 600 HP. However, when initially dyno'd, it made roughly 575 HP. This is where Ryan and his staff really shine! They take the time to expertly tune the motor and find "extra" horsepower and torque due to their years of experience with engine tuning! Don't ever settle for a crate motor. JGM will build a custom engine to your specific needs and have the experience to gain you the maximum horsepower for your hard earned dollar! read more

JGM Performance Engineering - 327 CI Built by Ryan at JGM - Auto Customization Near Me - Valencia, California

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I have been going to JGM performance for over 23 years. I first met Jim Grub the owner when I went into his shop to ask question about building my 351 W that I was going to use in my Cobra Kit Car. I also met Ryan who just started working for Jim. Ryan is now the owner of JGM Performance and Engineering. The first thing I notice was how Friendly an Professional both Jim and Ryan were. Jim answered all my questions, showed me around the shop. He then asked me what I was doing on (Sunday) this being a Friday.. I said I had no plans, he invited me to watch the Daytona 500 with a group of his friends. JGM engineering is by far the best machine shop I have ever been too. I have seen Jim and now Ryan when they are extremely busy, stop what they are doing to help a customer, answer all their questions, show them around the shop. Not many shops will do that. You are treated more like family than a customer. Their work is amazing, the details that they go into when machine a motor, heads, and the details when they assemble an engine are amazing. The skills that they have are truly amazing. This past Friday 08/29/2025 I drove in from Nevada because I had a problem. Ryan was extremely busy. He and Jerry were assemble a motor, yet Ryan took the time to help me with my problem. He explained and let me watch how to put a seal on my engine that I was working on at home. Not many if any shops would do that. This is why people come from all over to have their engines built at JGM. read more

!!BEWARE!! Jim Grubbs does well in charging plenty for his services but has trouble delivering upon his contractual commitments. He then blames everyone else and doesn't stand behind his work! read more

If you need engine work done, look no further. Ryan was straight forward, transparent, and always willing to take the time and effort to communicate through the process of working on my engine. Even after delivery he has been a amazing resource which has been a huge help. The work JGM did was excellent. They treated, even my very mild/stock build, with lots of care, making sure all necessary work was done at the highest level. Ryan kept me informed along the way with any challenges encountered and changes that needed to be decided on. I received exactly what I wanted, done as well as it can be, and left with valuable information that Ryan was willing to take the time to tell me. My experience with JGM was perfect. read more

Place is garbage and do poor work, spent over 10k , Ryan is great at blowing smoke up the you know what, I'm sure the past owner J.Grub did better work back in the day, long story short I had nothing but problems after they did my 455 olds motor from ground up, BUNCH OF YAHOOS THERE read more

I found JGM Performance Engineering through a friend who uses them exclusively. I took Ryan a standard bore SBC 4 bolt main block and a large journal steel 327 crank. I asked him to get the needed parts and machine me a short block that I would assemble. I realized that I was short on time, so I threw him a curve ball by asking him to get the needed parts and build me a completed 327. I also wanted him to run it on his dyno. He said no problem and made it happen. I am extremely happy with the workmanship and the final result. Ryan and JGM Performance Engineering will be my machine shop for all of my future needs. Paul read more

Ok building my BBF for my boat as we speak, Ryan the Manager of JGM is awesome, I'm a pain in the ass customer and even though he is beyond busy he still has time for my questions and thoughts. Motor is not done yet but they get 5 star for putting up with me lol. I will update after the motor is done. Thanks JGM / Ryan!! Update!!!! Motor dyno I was expecting 500-600hp and about the same torque. It made 671hp and 700lbs of torque This motor is going to be fun!!!! I can't thank JGM enough read more

JGM Performance Engineering - Auto Customization Near Me - Valencia, California

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Took our BBC 454 jet boat engine in to be completely rebuilt. Ryan and his team did an amazing job with a constant line of communication with any questions we had. Always felt encouraged to ask any questions. We also had the engine dyno'd at the shop as well. Everything was done in house, great customer service, and definitely will be back. Would recommend to anyone and everyone. read more

JGM Performance Engineering - Engine dyno - Auto Customization Near Me - Valencia, California

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The most recent review dated 07/14/2020 (1 star) is a complete contrast to my experience with JGM. I have called JGM more than once. I have spoken to at least 3 individuals at different times. Each representative was open to my questions and if they did not know the answer, they would get back to me in reasonable time as promised. Honestly, JGM provides service that is both personal with a family feel. With each interaction, JGM has proven to be completely transparent but more importantly, offering information that is relevant to your needs. In my opinion, this demonstrates a level of integrity that most businesses need to work on. Thanks JGM you have earned a lifelong customer..... read more

These guys are the best. Not only is Jim Grubbs a great honest guy but probably one of the most knowledgeable in the business. Their customer service is top notch. They have been doing great work on my 61 corvette engine and I wouldn't trust anyone else. read more

JGM Performance Engineering - Auto Customization Near Me - Valencia, California

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I was driving my 68 Mustang today with a 351 Windsor that was built by Jim Grubbs and had to come home and post on here for the first time in my life because it is so deserving. I have been beating on this motor and listening to it scream to 6700 rpm since 2002. Still runs like a champ and I couldn't be any happier listening to my engine rev over and over and over and over. Thank you Jim for making my car the fun of my life since 2002. I will stop by and rev it for you to enjoy as well. read more

JGM Performance Engineering - 351W by JGM - Auto Customization Near Me - Valencia, California

Great shop and great engine builders. I had a badly damaged pushrod and rocker arm. These guys helped me out above and beyond. Thanks guys for everything. I'll will be returning soon... read more

JGM Performance Engineering - Auto Customization Near Me - Valencia, California

A perfect 5-star rating for the guys at Jim Grubbs Motorsports! Terrific Family operation, super knowledgeable, honest and the highest level of integrity! Ryan and his crew did an amazing job building the engine for my 1970 Mach 1 Mustang, I loved the fact that my engine never left their shop. Every bit of block preparation, machining, blueprinting, assembly and the final dyno test was done at JGM. Ryan encouraged me to stop by the shop anytime and would even call me when good opportunities were present to take pictures to help me document my car build. "Old School Customer Service" at its best. When the engine was complete, I delivered it to Ventura, CA where my Mustang is being built. The car builder noticed that the dipstick that was originally in the engine was not the correct OEM dipstick that was supplied by the factory when the car was built. I contacted Ryan to schedule a time for me to bring the engine back to him to change out the dipstick tube in the block. Instead, Ryan volunteered to have one of his guys drive out to Ventura and change out the dipstick tube so I would not have to bring the engine back to him and then take it back to Ventura again. This speaks volumes for how they treat their customers... very rare to find this level of customer service and I cannot thank them enough. Do yourself a favor and trust these guys with your build, you will not regret it. read more

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Ryan and vinny rebuilt a tired old 302 engine we gave to them and did a phenomenal job. The engine was done exactly as he said it was going to be and kept us updated during the whole process. They always listened to my ideas and encouraged me to participate in every step. Ryan suggested changes which turned out to be improvements from the original plan. Definitely want to compliment them on sticking to their word and the plan and delivering an excellent product/experience. read more

My first engine rebuild and picked this shop due to good reviews. This is my experience: 2-3 months to fully rebuild and around $7k incl Carb rebuilt and Dyno was the job. Took 4 months and would have been longer if I did not push them. Carb was never rebuilt so when Doing the Dyno they were using their Carb ? What's the point in that. They forgot the do Carb rebuilt they said. Then my bill was $7200 , not incl Carb rebuilt and Dyno ( extra $1500 would be added) Then when paying the $7200 he added a quick $500 for some parts( basically I was paying for some Dyno work which I said I would not pay ) Totally not happy with this shop Never saw my engine running on their dyno , fingers crossed !! I sure hope their craftsmanship is as good as they say it is cause their customer service is something else. read more

Ryan is the guy! Just finished my 418 on his dyno! Nothing but professional stuff at his shop I will be back in a few weeks to build my giant! THANKS RYAN read more

Jim and his team are amazing. Beyond being honest and reliable (which they certainly are), these guys are the experts at building power into an engine. Their quality of machine work is unparalleled, their attention to detail is staggering, and their helpful attitude continues well after the sale. To give you an example of how seriously they take quality, Jim has his guys align the stamped printing on all the core/freeze plugs "right side up." Few shops would go to the trouble, but they do it without even thinking about it. That same detail-oriented approach pervades their work, with every measurement checked and re-checked, and every tolerance held tightly within a narrow range. I've never had a better experience with a shop, and I won't be going anywhere else for machine work as long as they're around. read more

Ok Here's the deal I was getting ready to get My engine in my boat rebuilt, And I was simply calling around trying to get the most information I could about my particular set up I knew they have built 540 marine engines which I was interested in doing. I had $18,000 set aside for the job. When I called in the guy seemed very annoyed that I was even asking about it And told me he didn't have anything to go on and he was extremely busy and basically acted like I was nothing, Even after I had told him what my goal was and what I had in my boat. Do they do good work? Probably but it really is a shame that he talked to me the way he did maybe they need to take a lesson on how to talk to their potential customers! Have I called other shops? Absolutely and I will continue until I find someone that acts like they are intrested in my business I've talked to a lot of different shops and this guy was the worst I have talked to by far totally rude about it. read more

These guys are as GREAT as it gets. Top notch engine builders. I had a Olds 442 engine (455 c.i.) built by Jim and his crew 2 years ago and it is still running perfectly. It was a stock type rebuild that they took from .040 over to .045 over so that there would be some rebuilds left in the #'s matching block. Custom grind on the cam, all the right machining and parts put it right at 385 HP and 498 ft. lbs. or torque. Very professional and priced right. I was able to be present for the dyno runs and I got to see the #'s with my own eyes. If you are looking for top quality rebuilds for your classic that holds up to the abuse of a lead foot, there is no other place. I give them 10 stars. Yes you could always find your engine cheaper somewhere else but I don't think you will ever find the Quality, support and customer service these guys provided. I have had many an engine built and none have run more consistent than the 455 they built. Highly recommended. A++++++ Service A++++++ Support A++++++ Quality They even painted the engine the correct color for the year, make and model. All bolts where correct as well, if your into that nut and bolt restoration kinda thing. And I am. Thanks JGM for a job done right. read more

Jim Grubbs is honestly the nicest guy I've ever met and puts in so much pride, dedication, and honestly into building his customers engines. Jim listens to exactly what you want the motor to do for you. JGM and the team rebuilt our '96 Ford F-350 460 V8 engine because we wanted more power and torque for towing. Jim turned it into a stroker motor that now produces over 400 HP and over 550 ft. lbs of torque! Jim puts so much pride into what he does and gives you honest opinions of what he recommends for the engine to operate at its highest level. I absolutely recommend going to JGM for any engine rebuild. His turn around time for the engine was only a few weeks which was amazing! I wouldn't go anywhere else but here. Jim even encouraged us to stop by time to time to see the progress of the build and he let us watch as it was being assembled, it was awesome! Thank you so much Jim for your awesome work and dedication! read more

JGM Performance Engineering - My Ford 501 V8 Stroker motor Jim built for my '96 Ford F-350 - Auto Customization Near Me - Valencia, California

Wanted to post an update now that my motor has about 50k miles on it and has pulled my fifth wheel everywhere. It runs better than ever and still amazes me every time I get behind the wheel. Jim and his guys are by far the best and to anyone that might read this, don't hesitate to have these guys build your engine! My 460 is a beast thanks to Jim........ read more